10 Things You Should Know About Charging Electric Vehicles

This is a recap of concepts I've covered at length in previous posts.

• 1) It's pointless to be able to "search for nearby charging stations," unless you're prepared to wait at least 1 hour for every 20 miles of charge you need.
• 2) There aren't nearly enough public charging sites to actually matter. If one happens to be in walking distance of a place you need to go, consider yourself lucky. (By the same token, if you know of a charging site at which you'd like to charge, it's not likely to be available - see #5.)
• 3) Yes, you can travel further than the full range of your EV's battery by stopping to charge. But if you do not plan carefully, you will either be stranded or find yourself sitting in your car for hours while it charges.
• 4) Public charging stations work, but how useful they are depends upon your level of commitment and/or spirit of adventure.
• 5) There's no guarantee or even likelihood that any given public EVSE will be available. It may be:
• non-existent
• non-operational (broken, or never completed as an installation project)
• charging another EV
• inaccessible because an EV or ICE (internal-combustion engine) vehicle is using the space only for parking
• 6) Even though most public charging stations deliver around 6-7kW (kilowatts), some don't.
• Those that can achieve at least 6-7kW replenish most vehicles at about 20 miles/hour. But some vehicles can only charge at about half that rate (i.e., some Nissan Leaf models have only 3.3kW chargers), and some public EVSEs don't provide more than 2-3kW, even to vehicles capable of charging at higher rates.
• 7) Most for-pay public charging stations provide a way for EV users who have not previously established an account to pay for charging.
• This involves a telephone call, a credit card, and a way to identify the charging station.
• 8) For-pay charging services may bill: a) by the hour of charging; b) by the kilowatt-hour (amount of electricity transferred); or c) by the hour of being plugged in (regardless of charging).
• 9) Regardless of your vehicle's battery capacity, the time required to replenish the battery at most public charging sites is about the same:
• Most "Level 2" EVSEs provide around 6 kilowatts, providing about 20 miles of range for every hour of charging.
• 10) For many users, public charging is irrelevant. If you don't drive more than 70 miles a day, don't worry about it.

Planning ahead to travel beyond the Single Charge

Because public EV-charging infrastructure is quite sparse, it's challenging to travel beyond a single charge. Making regular trips which require charging away from home can become routine. But with a little planning, even unfamiliar destinations beyond a single charge can be achieved.

I've made up the expression single charge to represent any round-trip travel which can be completed without recharging one's EV. It's an important concept, because things get considerably more complicated beyond what's possible on a full battery charge. When your vehicle only has a range of about 80 miles and takes 4 hours to completely refuel, time management is an important aspect of attempting trips which require refueling. In the four and a half months we've owned our first all-electric vehicle in Southern California, we've challenged ourselves to use our Ford Focus Electric, regardless of the destination. So far, we've never reverted back to our gasoline-powered vehicle. In that time, we've probably made only six or seven trips which necessitated a charge to return home. The longest round trip was exactly 200% of our battery range, for which we added about 15% - about 20 miles - of extra range. So we had to add 115% of a full charge while we were out and about - a total of about 5 hours of charging for a trip which took about 2.5 total driving hours.

In my previous posts, How Do I Charge My EV? and Why public EV charging stations might not be as useful as you think, I discussed the state of public charging infrastructure. The upshot of the latter post is that there's rarely a public charger where you happen to need to charge your vehicle, but the trick to charging on the road is deciding whether you can do something you already need to do where the EV charging is. This is obviously nothing like going to a gas station for a 5 minute fill up. But it can work, with a little thought.

Here are some important strategies we've developed and lessons we've learned:

• You can't have someone bring you a gallon of electricity. Emergency roadside EV charging trucks may exist somewhere, but I'm not counting on them anywhere. If you run out of charge completely, you'll be getting towed.
• You must be aware of how much real-world range you have, and how long it takes to add charge to your battery pack.
• It's tricky to anticipate how much battery charge a given trip will take. Many variables, including traffic conditions, elevation changes, and even the mood of the driver can affect EV range.
• Not all charging stations (EVSEs) charge at the same rate. Your plans can be torpedoed by a given amount of charge taking 6 hours instead of the expected 3.
• Figure out if there's something you can do wherever you find a charging station, for as long as you need to charge.
• Meals are the most practical solution; shopping can work as well. Most EVSEs are located in or near retail areas, so both of these services are likely to be within walking distance. 
• To avoid charging in an unfamiliar neighborhood after dark, try to charge on the outbound leg of the trip earlier in the day.
• We prefer to charge on the road before an appointment or event, so that (assuming it's a one-charge trip) we won't have to think about it again after the event. 
• Charging infrastructure is flaky and unpredictable. Never assume that your planned primary or even secondary charging locations will be functional or available. Plan to have enough charge to drive to another charging location.
• Many townships here in SoCal have a municipal (often free) charging station. But they're typically located in a parking lot at city hall, which may not be a place where you want to walk or sit in your car after dark. 
• If you see a car plugged in at a charging station, don't assume they'll ever leave. We've seen several cars in shopping center EV spaces that were there for 8+ hours.

CHARGING STRATEGY EXAMPLE

Let's put some of this wisdom to work in a scenario:

• We're traveling to a destination that is 40 miles away, over unknown terrain (we don't know about elevation changes, which soak up a lot of range). So our round-trip is 80 miles, and we'll be traveling on Los Angeles freeways.
• Worst case for battery range, traffic will be light and fast, and we'll travel at 65mph or faster (because of aerodynamic drag, traveling 60mph uses 4 times the energy of going 30mph).
• The nominal range of our battery pack is about 80 miles at 60-65mph on level ground.
• This can increase by a substantial amount if the traffic is slow, but I'd only count on going 70-75 miles.
• Turning on the heater in our Focus Electric's climate control can reduce range by more than 30 per cent.
• I'd like to have at least 10-15 extra miles of range than anticipated.
• On a 240 volt, 30 amp Level 2 charging station, our EV will add 20 miles of range to its battery every hour. This is a typical rate for most EVs. (Be warned that some L2 EVSEs are configured to charge at a lower rate. However, most will achieve the 30A rate.)
• So if our battery delivers 75 miles of range, and we add one hour of L2 charging, then 75 + 20 = 95 miles. That's about 15 extra miles over our 80 mile target. 
• We want to add 20+ miles of range at some point during the day. We'd prefer daylight hours. 
• We can't add 20 miles of charge until we've used at least 20 miles of charge. So we use tools like PlugShare.com to locate a charging station that is on our route, and at least 20 miles away from home.
• We use the Yelp! links and other search engines to determine if there are dining/shopping establishments close to the located charging site.
• We also locate a few contingency charging sites further down the route, in case the first choice fails.
• Online and smartphone EV charging location-finding tools promise to show real-time status of whether chargers are in-use, but that doesn't help if someone plugs in 30 seconds before you arrive, or are parked in the space but not connected to the charger (and thus EVSEs don't show "in use" status).
• We stop at the scheduled charging site, and (assuming that the charging station is available and operationalI) have a leisurely 1+ hour meal or shopping trip.
• Using smartphone apps on for our car, or from the charging services, we monitor our car's charging progress. The car and charging network apps notify us when the car has completely charged (if we choose to let it reach full charge). 
• With a full battery, we complete our day's journey, knowing that we have 10+ miles of surplus charge for unexpectedly high power consumption or a (small) side-trip.

Based on the experiences and criteria I've mentioned above, online and smartphone tools for planning EV trips and finding/using charging locations aren't very good at this point. Most of them prioritize finding a charging site nearby. If you are looking for a way to charge your EV nearby, you're probably too late. No EV owner would think this way for long. Ideally, the tools should put as much emphasis on what else you can do while charging at a given location as the charging itself. You may be waiting for many hours for your vehicle to charge, so you'll really want something to do while you wait. And navigation tools (including EV in-car navigation systems) should take elevation changes into consideration for range estimates.

GOING TO GRANDMA'S HOUSE  

If you have a good relationship with the home or business owner at your destination, this opens up the possibilities of charging at both ends of your commute. The important parameters are:

• the charging rate of your charging hardware
• the "Level 1" EVSE (discussed in my earlier post) included with most EVs charges at 3 to 4 miles per hour; Level 2 EVSEs that are typically permanent installations charge at 15 to 25 miles per hour
• there are portable L2 EVSEs (we chose to purchase a "plug-in" L2 EVSE in the event that we think we might have access to 240 volt, 30+ amp connections "in the field") which can be transported with the vehicle
• if the destination is frequent, you may choose to permanently install an L2 EVSE there, but the cost of hardware and installation isn't trivial
• how long you'll be visiting
• The math is simple: required miles to complete journey / charging rate in miles per hr = hours to charge
• how much charge you need to return home
• Depending upon how much battery charge you have upon arrival, how far the return trip is, and how much surplus you want as range insurance.

EXAMPLE: When you arrive at Grandma's house after a 60 mile drive, your EV shows 20 miles of remaining range. You need at least 40 miles of additional range (but it may take more or less power to make the reciprocal trip on the same route, depending upon elevation changes or traffic), and you'd like 10-15 mile of "pad." 

If you have a Level 1 EVSE and plug into a 120 volt outlet in Grandma's garage:

55 miles to complete journey / 4 miles per hour @ L1 = 13.75 hours

If you have a portable Level 2 EVSE, and use an adapter to plug into the outlet for Grandma's electric oven (and Grandma isn't planning on baking cookies for you while you're there), or you pay to have an electrician install a 240 volt, 30 amp outlet for your EVSE at Grandma's:

55 miles to complete journey / 20 miles per hour @ L1 = 2.75 hours

So if you're spending the night at Grandma's or don't mind listening to her talk for 14 hours, you can get by with Level 1 charging. But if you had L2, you could just have a meal, watch an episode of "Murder She Wrote," and go home. 

Will Grandma mind you using her electricity? She might, but in this example, with our Ford Focus Electric and at 20 cents per kilowatt hour for electricity, that 55 miles of charge would cost about $3. You can leave it in her tip jar, if you think she minds.

THIS IS A LOT OF TROUBLE, ISN'T IT?

Many, if not most EV owners won't attempt journeys which exceed a single charge. That's really the expectation of manufacturers who are selling EVs now, and of consumers who purchase them with full knowledge of their range limitations. 

Sure, this is a lot more effort than using an internal-combustion vehicle. With most conventional cars, you could make at least two of the round trips in the example above on a single tank of fuel. But if you've read this far, you might just be the adventurous sort who welcomes such challenges of EV ownership. 

Regenerative Braking

Back in 1999, we rented the now famous GM EV1 on a couple of occasions. Long interested in both automobiles and technology, it was only natural for me to be interested in what that project attempted and accomplished.

One of the common press buzzwords for the EV1 was "regenerative braking." GM engineers would refer to it as "regen." They promise of regen was that the EV1 would attempt to recoup some of the energy wasted during deceleration. This energy would put back into the battery pack, rather than lost as heat, as is the case with traditional internal-combustion vehicles and friction braking systems (which the EV1 also utilized).

After reading much hype about the complex engineering and motor/charging control system programming involved in the EV1's regenerative braking system design, I was disappointed when I finally saw empirical data of the increased range. I think that GM claimed something like three or four additional miles of range, and though the EV1 publicized a maximum range of over 100 miles, real-world range was more like 70. So the benefits were single-digit percentage of range improvement, at best.

To be fair, if they really got 5 or 6 per cent improvement, that's pretty impressive, especially given that those first-generation EV1s used lead-acid batteries. Lead-acid batteries take on charge at a significantly lower rate than the lithium-ion and lithium-polymer packs that power today's EVs and hybrids.

Most if not all of today's mass-produced plug-in electric vehicles and hybrid vehicles employ some sort of regenerative braking system in an attempt to increase the range/efficiency of these vehicles. The millions of hybrid vehicles that have been sold utilize regenerative braking systems and small battery packs to improve the energy efficiency of those vehicles.

SO WHAT IS REGENERATIVE BRAKING?

The idea behind regenerative braking is to exploit any opportunity in which the momentum of the vehicle needs to be diminished, and store as much of this energy harvested from either slowing the vehicle or maintaining speed while decreasing altitude on a downhill grade. The friction brakes employed in automobiles (including EVs) convert momentum into heat. When the throttle is lifted on an internal-combustion vehicle, the the vehicle's momentum is also converted into heat at it compresses air pumping through the engine (in a manual-transmission vehicle) or churns the fluid inside the automatic transmission's torque converter. In pursuit of greater efficiency, vehicles with regenerative braking attempt to replace these traditional momentum-transferring mechanisms with systems that store as much of that energy as possible for later use.

Beginning almost a century ago, commuter light rail cars and buses have used mechanical storage mechanisms for this purpose, either spinning up a heavy flywheel or even winding a large spring mechanism as part of the braking system. When these frequent-stopping public transit vehicles were ready to depart for the next stop, the operator released the mechanically-stored energy to assist the vehicle's normal propulsion source in getting the vehicle moving from a standstill. Crude as these systems might seem today, the ideas are still valid (and still in use, in some cases) and provide useful energy-reducing benefits by salvaging some of the energy normally lost as heat.

Today, in addition to the more well-publicized electrical battery regen systems employed in vehicles, there are ultra-high pressure compressed gas batteries used in urban public transit and delivery vehicles in much the same way as those flywheel and spring systems, to store as much energy as possible from any given stop to offset the enormous task of overcoming the loaded vehicle's inertia when stopped. Though none have been put into practical use in vehicles, many experiments have utilized high-speed electrically-powered flywheels as batteries for storing and returning energy from braking.

ELECTRIC REGEN

Electric motors and electric generators are very similar. Indeed, many electric motor designs function very well as generators.

Thought Experiment: Two identical, high-efficiency, permanent magnet electric motors are mounted on a tabletop. On each of these motors driveshafts is mounted a hand-crank. Between the two motors are connected two wires, so that the two motors and wires complete a circuit. If the hand crank of one motor is spun with sufficient speed and force, the other motor will begin to turn. If instead, the hand crank is turned on the second motor, the first motor will turn from the electrical energy passing through the circuit. If while turning the "generator" crank someone else places a load on the "motor" - perhaps by dragging their hand on the motor's spinning shaft/crank, the person cranking the generator will feel the effort increase. Likewise, if a low wattage light bulb powered by the generator is replaced by a higher-wattage bulb, the generator operator will feel the additional effort. Note that when these experiments are performed, both motors, the light bulbs and the wires are likely to become warm to the touch. Some of the heat is from mechanical friction from the moving parts of the motors, but most is from electrical resistance. This is evidence of energy leaving the system in the form of heat, and thus a loss of efficiency. This loss is in practice unavoidable. 

Electrically-based regen systems use an electric generator - typically the very same electric motor used for propulsion - and an electronic control system to reverse the flow of electrons from the battery to the motor whenever the system detects an opportunity to do so. As in the thought experiment above, applying regen creates a torque load in the opposite direction of travel to wheels connected to the motor, so regen systems must be designed not to upset the stability of the vehicle through excessive application of this braking torque (i.e., locking up the driving wheels in slippery conditions because the braking torque is too high). But it should be as aggressive as possible to reap the maximum efficiency.

Regenerative braking systems will attempt to "harvest" the momentum of the vehicle under several conditions:

• when the driver applies the brake pedal
• the regen system attempts to achieve maximum generator braking torque, but if this is inadequate to the request signaled by the driver's brake pedal pressure (i.e., an emergency), then the friction brakes must work in concert, and have priority
• if the brake pedal pressure is below a certain threshold, then the system has the opportunity to modulate braking torque entirely through regen, with no friction braking
• below a certain road speed, motor regen no longer generates effective braking torque, and so a transition from regen to friction braking must take place during a full stop
• A common malady of vehicles employing regenerative braking is that the transition to friction braking is typically non-linear. Most often (at least in my regen driving experiences of about a dozen different vehicles), there is a sudden increase in braking effect as the friction brakes take over. I think this is chosen as a more desirable transition than having the braking effect suddenly diminish, but it causes drivers unfamiliar with those cars to nose-dive during this "grabby" increase in braking effect. With some practice, one learns to feather off the brake pedal just at the transition. 
• when the throttle position is insufficient to maintain current speed for the current conditions
• when the vehicle encounters a downhill grade or tailwind
• the regen system will attempt to convert excess momentum to battery charge
• depending upon how much the throttle is lifted, and which regenerative braking mode is selected, the system attempts to slow the vehicle with motor braking/regen

Different manufacturers have different philosophies and strategies about how aggressively their regen systems attempt to harvest. Some vehicles (including our Ford Focus Electric) provide the driver with feedback for driving behavior that maximizes regenerative braking gains. These vehicles coach the driver with visual display aids to generally brake over longer distances at modest deceleration rates, which allow the regen system to perform nearly all the speed abatement, while using the friction brakes as little as possible to avoid needless energy loss as heat.

It's important to grasp that it's impossible to recoup all of the energy from a moving vehicle's momentum with a regenerative braking system. Some energy will inevitably be lost as heat from friction and other mechanical inefficiencies, and there will be loss in electrical and electronic control systems. But systems have become efficient enough for vehicle manufacturers to profit by manufacturing and selling them, and for vehicle owners benefit from measurable energy-use reductions. If you drive up a 400 foot incline and the regen system harvests during the 400 foot descent, you still use significantly more energy lost as heat than if the road were level.

IS DRIVING A CAR WITH REGENERATIVE BRAKING DIFFERENT?

I would say that there is a place and time for a car's regen to be completely undetectable, but for certain users - particularly the current crop of early-adopters of EV and regen technology - having noticeable differences in operation due to regenerative braking is a desirable trait. Certainly those vehicle owners who wish to take a more active role in exploiting the energy-saving benefits of EV technology - the same population who coined the term "hypermiling" to describe challenging oneself to drive their vehicle while using as little fuel as possible - are not only willing to accept additional consequences of the technology, but embrace them.

REGEN-BRAKE TRANSITION

As much as manufacturers would like to make cars with regenerative braking seem absolutely no different to the user than any other vehicle they've operated, such has (in my opinion) not yet been achieved. I haven't driven every vehicle equipped with regen, but I've driven several examples from many different manufacturers, most of whom have developed their own regen technology. And they all suffer from a similar issue which I'll call poor regen-brake transition.

A difficult task engineers face with regen is that for maximum recovery of energy during deceleration and hill descent, friction-braking should take as little part in the process as possible. But for reasons of safety, cost-efficiency and common sense, friction-brakes must be part of the vehicle's braking system. This is partly because the electrical braking torque available in a given vehicle regen system is never adequate for maximum braking, and because electrical generators no longer function effectively below a certain rotational speed. So during a given traffic stop, the system controller will somewhat suddenly hand over braking duties from regen (or a mix of regen/brake, during heavier braking) to friction-brake only. Because electrical braking torque is dependent upon battery load in a regen system, there are conditions under which regen is typically unavailable.

During a typical traffic stop, the EV's control system will attempt to harvest as much energy as possible during the moments that the driver indicates that they wish to lose velocity by pressing on the brake pedal. If the brake pedal is pressed moderately over a long, gentle stop (which several EVs encourage through dashboard brake-coaching displays), the motor controller will keep the wheels engaged to the motor - now functioning as a generator - and route the generated power into the battery pack. If the brake pedal pressure indicates a need for braking which exceeds regen, then traditional friction brakes continue to work as in a conventional vehicle.

ALTERNATE REGEN MODES

Many vehicles with regenerative braking offer two distinctively different regen modes, both of which actually affect the behavior of the vehicle with respect to throttle (and perhaps should actually be called "throttle modes"). Neither of these modes causes the vehicle to behave as a typical internal-combustion vehicle with an automatic transmission. The two modes have varying names, but the concepts are the same:

• Normal, "coasting" mode - When the throttle is lifted, the vehicle provides NO additional braking force except mechanical friction from moving parts and aerodynamic drag. Because most EVs and hybrids deliberately use low-drag bodywork and even tires, very little speed loss results from decreasing the throttle at medium and low speeds (where aero drag has less effect). In the most extreme case of differences between Internal Combustion (IC) cars and low-resistance EVs, lifting the throttle may give the driver the impression that the throttle is still applied, because the deceleration is nearly imperceptible.
• IC cars with automatic transmissions provide significant "engine braking": the engine is partially coupled to the road wheels through the torque converter, and when engine speed is reduced, a braking torque is applied to the wheels. So we're all accustomed to a certain deceleration rate when we lift off the throttle. EVs in "coast" mode barely slow down in an attempt to preserve momentum.
• "Low gear," "Braking," or "Regen" mode - When this mode is selected (often using the vehicle's "shifter," even though this is actually an electrical or software change), the regen system responds to any reduction in throttle position immediately, aggressively slowing the vehicle through electrical braking torque, and sending any harvested electrical energy to the battery pack for storage. Manufacturers have a difficult time explaining this mode, and why the user might employ it. Most manufacturers present the feature in much the same way as manually selecting a lower gear (2nd or 3rd gear) in an IC car with an automatic transmission to provide engine braking on long downhill descents. But then, most people never use that feature of IC cars, and most people with EVs won't do a lot of long downhills. My thoughts about Braking/Low Mode:
• To get the most out of regenerative braking, I drive in this mode most of the time, except during high-speed highway driving. However, it takes a bit of practice to drive smoothly.
• This is far more demanding of the driver. Driving in this mode requires disciplined control of your throttle foot. In most EVs, I liken the effect to driving a 5-speed manual vehicle in a gear about halfway between 2nd and 3rd. Lifting abruptly off the throttle in this mode at 60 mph causes enough deceleration that it could alarm passengers, and in traffic, creates the potential hazard of slowing you significantly while not activating brake lights. With throttle practice and experience, it need feel no different than any other car.
• There is NO DIFFERENCE between holding the throttle in a position in this mode that slowly loses speed and lifting off the throttle in "coast" mode.
• It would certainly be possible to use more energy through unnecessary slowing in this mode.
• I recommend against using this mode while using cruise control, since canceling cruise then results in somewhat more abrupt slowing than conventional cars.

NOTE: I presented the tabletop generator/motor experiment to illustrate that the braking torque utilized in regenerative braking systems depends upon an electrical load. In the case of regen, that load is a partially-discharged battery. In the case of our Ford Focus Electric, if I leave home with a fully-charged battery pack and put the car in "Low" mode, I get no braking torque effect for the first mile or so of operation, because there is no discharged battery to provide a resistive load. In fact, occasionally if I happen to be in Low and braking for a traffic stop during that first few minutes of operation, the Focus might abruptly slow as it suddenly adds regen braking torque when the battery pack falls below full charge. Toyota Prius hybrids apparently maintain their batteries at around 40 to 60 per cent of their full capacity, so that they can always have "headroom for regenerative braking." 

SO WHICH REGEN MODE SHOULD I USE?

If this all sounds like a lot of trouble, don't worry about it. Just select the default drive "coast" mode and have a good life. You may initially feel as though your car isn't slowing down as much as it should when you lift off the throttle, but that's by design. 

There is lively discussion in online forums about which of these modes is "best," or most efficient. Personally, I prefer the idea that if I see an opportunity for maximum regen harvest (a traffic light turns yellow ahead), that it's easier to fully lift off the throttle than to apply only enough brake pressure to trigger regen, but not so far that I waste precious momentum in friction braking. So thus far, I've tended to stay in "Low" mode in our Focus Electric as much as possible during city driving. I operate in Drive mode on the highway to avoid subjecting cars behind me to unexpected slowing without any brake lights, but if I slowing traffic or am approaching an impending exit ramp, I'll throw the vehicle into Low mode for maximum regen. I'm an "involved" driver in any kind of vehicle, so this isn't an imposition for me, but for most drivers, I think this would be too much to do. (I intend to experimentally drive in normal Drive mode for an extended period to compare efficiency results.) Initially, it may be tricky to gently transition off-throttle, but as with most things, one becomes accustomed to it with practice.

HOW WELL DOES REGEN WORK?

Our Focus Electric reports than in 2,885 miles of operation, 627 miles were from regenerative braking. Since I have no way to disable its regenerative braking, I can't provide a comparative figure, and I have to take their word for the reported figure. But if it's accurate, then regen has saved us almost 28% of our energy cost.

(I just noticed for the first time that our Focus Electric has occasionally logged my wife's wireless key fob as the current driver, even though I've almost exclusively driven the car. And the dashboard display only shows statistics from the currently logged key fob. So I just updated the figures above to reflect the 159 miles previously excluded from calculation. That makes for an even more impressive effect than the 19% energy savings I previously cited.)

While the big picture of ecological impact of the manufacture, servicing and recycling of battery electric hybrids is still in question, manufacturers and government organizations have been convinced enough of regenerative braking's validity that increasing numbers of automobile models are adopting the strategy to achieve energy and emissions goals. 

As energy storage technologies continue to mature, regenerative braking will play a incrementally larger role in our energy and transportation future.

Choosing a "portable" Level 2 EVSE

As I was researching EVSEs to install at our home, I discovered a distinctive characteristic that there were "plug in" models, which typically use a NEMA 6-50 plug and receptacle to connect the EVSE to an AC electrical supply, and "hard wired" models, which are to be permanently connected to an electrical supply. Some brands only sell one version or the other, and some are available in both connection options. In some cases, there were subtle differences between features, such as the length of the cable between the EVSE and the vehicle connection plug.

I was immediately interested in the notion of having a "portable" Level 2 EVSE. I don't know if that's ever going to come up, but if we ever did try to drive a long distance in an EV (in our current Ford Focus Electric, that would mean driving for one hour, then charging for 3 and a half, then repeat), we'd want to have as many charging options as possible. If we have to stop at a friend's house to top off, we don't want to have to stop for 20 hours with our Level 1 charger - we'd like to have a 3 hour meal/visit and hit the road again. It's not something I expect to do more than a few times, but I'm up for that adventure, and I like to have my options.

I was considering adding my own NEMA 6-50P plug to some EVSEs which were only available hard-wired (some people refer to the end of wires without terminals as a "pigtail"), but then noticed a subtle mention in one manufacturer's collateral material that their plug-in model claimed to incorporate ground fault circuitry, but their hard-wired made no mention of GFI. This may have been a typographical error, but it made me wary of adding my own plug, and it wasn't a deal-breaker to eliminate that brand from my candidate list.

In the end, we bought an Aerovironment "Plug in" EVSE for a few reasons. I've used public installations of them, so I know they think they're rugged enough for years in that fully exposed environment (we installed ours in a covered breezeway, as we're currently parking our EV in our driveway, due to conflicts with other garaged vehicles). And the Aerovironment piece is, while not exactly small, certainly far from the biggest of the EVSEs out there, all of which do the same task. Our Focus Electric gave up a LOT of the Focus' original cargo compartment to its battery pack, so keeping things compact helps. Finally, I established early on that the Aerovironment mounting bracket and EVSE incorporate a hasp for a padlock, so I can secure it (at one point, I was going to mount the EVSE on the front of our house near the street). It's also a "quick release" bracket - although the tolerances between the EVSE and mounting bracket are a bit too close, and it's not at all easy to remove. That said, I don't expect to remove it much, so it's not a big deal.

We had an electrician run a custom 50 amp, 240 volt circuit to a NEMA 6-50 receptacle on our breezeway wall (the EVSE and our car require only 30 amps, and specify 40 amp service, but the electrician ran wire big enough for a little future-proofing). Local code required that in this "damp" location (even though it's under our continuous roof), the receptacle be installed inside a "weatherproof" enclosure.

Aerovironment "Plug In" EVSE, with NEMA 6-50 outlet in "damp location" mandatory weatherproof enclosure.

I still haven't gotten around to collecting the pieces, but theoretically, with a few inexpensive adapters, we'll be able to charge from household electric clothes dryer or stove circuits (provided they are 240 volt, 30+ amp), and campgrounds (via their 50 amp NEMA 14-50R service, if they have it).

We might never try going more than a couple of full charges from home, but if we do, I'll be ready for it.

Cabin Heat - the Enemy of EV Range?

THE FREE (HEATED) RIDE IS OVER

For the past century of internal-combustion (IC) powered automobiles, we've taken for granted the luxury and convenience of having heat (unless you owned an air-cooled Volkswagen, but that's another topic). When we've needed heat to maintain comfort (or in more severe climes, to survive), or clear the windshield of our IC cars, we've used "waste heat," excess thermal energy which is a side-effect of IC power. This excess heat is conducted away from the hot combustion regions of the IC engine and into the air around the vehicle. So using some of this heat before it's simply exhausted from the vehicle is for all practical purposes free. We incur almost no energy consumption consequences when we turn on the cabin heat in our IC car. (Actually, in extremely cold conditions, some IC vehicles can have trouble reaching a sufficiently high engine temperature for efficient combustion and oil viscosity. So in these cases, turning on cabin heat might further over-cool the engine.)

The amount of energy required to maintain human-comfortable temperatures in a poorly-insulated metal box which is constantly being cooled by 65 mph, 10 degree Fahrenheit air flowing over it is impressive. While there are parts of EVs that get warm during operation, there isn't nearly the amount of excess heat that has been available in IC vehicles. So EV manufacturers have had to resort to using some of the precious stored electricity from the vehicle's battery to make heat. The heating system in our Ford Focus Electric, and probably most EVs, is a resistive heater. A resistive heater uses electricity to heat conductors - wires - over which cabin air is drawn. The shocker is how much power the heater draws. My calculations (see below) suggest that the heater uses almost 7,000 watts of power - slightly more than a typical home electric oven.

GM's pioneering EV1 and Toyota's 2004 RAV4 EV incorporated "heat pumps" to heat and cool the interiors, but I've thus far found no evidence that any current EVs are employing that technology. Heat pumps, while power efficient, work somewhat slowly at moving heat from one place to another, and would probably be a poor choice for an environment in which the entire volume of the cabin could lose all its heat during the 30 seconds it might take to buckle the kids into their seats.

When I turn on the heater in our Focus Electric, its range estimate falls by slightly more than 30 per cent - it is assuming that I'll leave the heater on for the entire journey (which is one of many flaws of range estimation). In many cases, the heating system will be able to reach the desired temperature so that either I or the thermostat will turn off the heating element. When I tested the range impact for this article, the full-charge range estimate (which varies based upon the previous driving cycle) for the Focus at the time was 91 miles, and I estimate that the Focus would have to be traveling at 60mph on level ground in moderate temperatures to achieve that. The Focus' battery pack has a capacity of 23 kilowatt/hours (kWh). So we can extrapolate that for our 2013 Ford Focus Electric:

• 91 miles @ 60mph = 1.5 hours
• 23 kWh full battery / 1.5 hours = 15.33 kW (20.56 horsepower) @ 60 mph  
• 91 miles no heat / 63 miles with heat = 1.44 = 44% more power with heat
• 0.44 heater coefficient x 15.33 kW @ 60 mph = 6.75 kW heater power 

So our Focus Electric's heater has a devastating impact upon range. In the worst case, a new EV owner might spend the entire spring and summer season commuting 60 miles to their workplace and back, arriving home each evening with 15 surplus miles with which they could run errands before recharging. But when the winter arrived, they'd discover that in addition to some range lost to battery efficiency at low temperatures, they would be unable to complete the same journey while maintaining any sort of cabin heat. We live in Southern California, and our Focus has heated seats (I envy Chevy Volt owners' heated steering wheels). So down to the low 40s, we've made do with being a little bit cooler and cranking up the seats (which have no noticeable impact upon range). But if you lived in a really cold place, you'd have to deal with a lot of discomfort, or come up with an additional charging stop.

In our Focus Electric, which has an "automatic climate control system," selecting any temperature that's even a single degree above the current cabin temp will energize the heater, and cause the range estimate to plummet until it reaches that target temp. The same is true for the Defrost mode. So it's a bit more involved to use an EV's climate system if the intended journey approaches the ultimate range of its battery pack. The Focus Electric is what I call a "conversion" - it utilizes many parts and systems from the existing Ford Focus internal combustion car it's built alongside. The "legacy" HVAC (heating, ventilation and air-conditioning) control system operates as blithely unconcerned about power consumption as it does in IC vehicles, and every time I call for a little fresh air, the HVAC gleefully turns the fan on full blast and cranks up the heat or A/C compressor, forcing me to frantically start poking at its controls to limit its effect upon vehicle range. A vehicle purpose-designed to be an EV could and should incorporate systems and operational modes which are more energy-aware. I wish that the Focus Electric had a low-power heating element just to keep the windshield from fogging. Instead, I engage the mighty 7 kilowatt heater system and watch the battery gauge instantly plummet to 2/3 of its previous range estimate.

If you operate your EV in a region with frequent or prolonged periods of intense cold, you should consider that its maximum range could dramatically change during the cold season due to heater use. Here are some strategies to limit the range-reducing effects of using cabin heat on an EV:

• Bundle up in a lot of clothes and avoid using the cabin heat. However, it can be impossible to go without turning on the defroster. When it's cold outside and you're exhaling inside, you eventually end up with either fogging or frosting condensate on the inside of the windows. In our Focus Electric, there is little choice but to engage the power-sapping heater when the "defrost" function of the HVAC system is called. 
• Use cabin preconditioning to preheat your vehicle while still connected to a charging source. In addition to passenger comfort, this helps with interior defogging and exterior defrosting (when parked outside), but at no small cost in electrical energy from the utility company. Much of this cabin heat will be quickly lost in very cold conditions when in motion. If there are no charging facilities at the other end of the commute, preconditioning will be unavailable for the return trip. Cabin preconditioning, while not affecting battery range, does have its cost (see "Cabin Preconditioning" below).
• Use the heat sparingly. In the pursuit of range, we're willing to have a cold cabin. But I'm far less cold-averse than most people, and if it were REALLY cold, or had passengers, I'd still want some heat. We use our seat heaters in lieu of cabin heat whenever possible. We're all used to being warm and toasty in an IC car. I don't see that happening without significant consequences any time soon in an EV. 

Of course, if your journeys use only a fraction of a full battery, and you don't mind using more energy, you can crank up the heat and stay toasty warm. Even then, you'll be spending less on energy and have a lower carbon footprint than you would in an IC car.

CABIN PRECONDITIONING - A HIDDEN COST?

An oft-mentioned feature of modern electric cars is "cabin preconditioning" or "climate preconditioning."  And for the 15 years I've been hearing about it, I've found it both an appealing idea - your car is already warm in the winter, or cool in the summer - and what sounds like a perfectly logical strategy for an electric car: that you use your home's boundless electrical supply so that your precious battery charge can be preserved for propulsion.

. . . and work it does. Our Internet-connected Focus Electric provides on-board and remote (via website or smartphone app) programming of "Go Times" - the anticipated time of departure. Select one of the preset temperatures, and for the 15 minutes prior to the Go Time, the climate system attempts to reach and maintain that target temperature. Alternatively, the user can "Remote Start" the Focus Electric (a funny expression, since there really is no "starting," per se, except to put the car into Drive mode, which is decidedly NOT what you want to do when you're not in the car) from key fobs, smartphones, and the Web. If the user is prescient enough to leave the climate system in the "on" position and set to a target temperature (I'm so focused on managing power, I don't even run the climate control beyond getting barely comfortable while in the car), the remotely-started Focus will attempt to achieve that temperature for a maximum of 15 minutes.

Again using our extrapolated Focus Electric data:

• 6.75 kW heater x 15 minutes / 60 mins in an hour = 1.69 kWh per 15-minute precondition
• 23,000 watt hour battery / 91 miles = 253 wH/mi @ 60 mph
• 1.69 kWh 15-minute precondition / 253 wh/mi = 6.67 miles @ 60 mph

So a single morning's 15-minute precondition cycle would be equal to almost 7 miles worth of highway driving. Assuming you preconditioned just once each weekday morning, that's 21.67 avg weekdays/month x 1.69 kWh = 36.62 kWh/month. Using our (Los Angeles DWP, late 2013) highest tier electrical rate of about 20 cents/kWh, that's $7.32/month to precondition your cabin. That might not seem like a lot, but I drive our EV 5 miles every day of the month with that much electricity.

And that doesn't even take into consideration that you might turn on the heat while you're driving.

So cabin preconditioning is nice. There's the convenience of getting into a car with a comfy cabin and a clear windshield. But if you are interested in EVs because you want to reduce your energy footprint, just know in advance that cabin preconditioning can have significant energy-use consequences.

AIR CONDITIONING - NOT THAT BAD (SO FAR)

In the case of our Focus Electric, the energy impact of turning on the air conditioning compressor to cool the interior or de-fog the windshield appears to be far smaller than the heater. During the same test I performed with the heater, turning on the A/C dropped the Focus' range estimate from 91 miles to only 89 miles - representing only a few hundred watts of power. This is pretty impressive, given that just 30 years ago, automotive air conditioning compressors used as much horsepower as our EV does to move through the air at 55mph. We haven't yet used the vehicle in the truly hot weather that we can get here in SoCal, so we don't know how high temps will further reduce battery range, or whether the Focus' high-efficiency electric A/C compressor can refrigerate well enough to keep us comfortable in triple-digit weather. I'll report as I can.

During our first month of EV ownership before our Level 2 EVSE was installed, I plugged our Level 1 EVSE through a Kill-A-Watt. This product is an electrical energy logging device, intended to let consumers determine how much energy any given appliance in their home uses. When I compared the Kill-A-Watt's logs to the Focus Electric's on-board log of energy use, I discovered that the Kill-A-Watt reported over 30 per cent more energy use than the Focus - and this was without doing any cabin preconditioning. I have no way of knowing whether the Kill-A-Watt or Focus are accurate or not in their data logging, but the suggestion is that the car's records might not reflect the amount of electricity actually pulled from the energy grid and billed to the user. This does make sense - the car isn't responsible for whatever inefficiencies there might be in the rest of the power transmission process. But the point is that an EV's historical log of electrical use probably doesn't present the entire picture of electrical cost-of-operation. The Kill-A-Watt is 120 volt, 15 amp maximum, and can not be used with our 240V, 30A L2 EVSE. I intend to install a separate energy logging system in our home electrical system to accurately determine how much energy the EV is using - if I do so, I'll report that here.

Why public EV charging stations might not be as useful as you think

One of the first things most new or prospective electric vehicle owners research is the locations of public EV charging stations. 

ELECTRICITY, ELECTRICITY EVERYWHERE, BUT NOT AN ELECTRON TO CONDUCT

We live in Los Angeles, an enormous city where many of our friends think nothing of driving 45 miles (still in Los Angeles County, mind you) to grab a bite to eat. L.A. has as large an electric vehicle fueling infrastructure as currently exists - which is to say, a lot more than most of the United States. Still, there's not enough of a network of charging facilities that you're likely to be able to plug in your vehicle where you happen to be going.

A brief online search suggests that there are around 120,000 gas stations in the United States. That averages to one station per 2,700 citizens. So California, with 38 million residents, should have around 14,000 gas stations. According to the U.S. Department of Energy, as of January 2014, there are 5,176 non-residential electric vehicle charging stations in California. However, some of these are so-called "legacy chargers," which may not have ever seen any significant use beyond promotional propaganda a decade ago. In practice, public charging stations are far more sparse than those numbers suggest. Even though a few modern companies are maintaining networks of paid public charging stations (and there are still some legacy free charging stations left over from various utility and municipal trials and promotions from the past 15 years), there are not nearly enough stations to be called ubiquitous. Their usefulness is severely limited by their scarcity.

EV charger-locating site PlugShare's map of Metro Los Angeles illustrates that even in the middle of densely-populated L.A., you could easily end up walking 3 miles - one-way - to and from the nearest charging site.

So while California might lead the way in public EV charging stations, that's not as meaningful as it sounds.

CURRENT PUBLIC EV CHARGING INFRASTRUCTURE

In our first weeks of EV ownership, I explored the available public charging infrastructure. We established accounts with the handful of companies maintaining for-pay charging networks. One of those companies, ECOtality, declared bankruptcy during our second week of ownership and its new owner is still struggling to reestablish a business with its network of Blink charging stations.

During our first couple of days with the Focus Electric, I drove around and located the public charging stations near our home. Several things about public EV charging became apparent:

• EV charging stations are where they are, not where you want them. There aren't nearly enough that your destination is likely to be within reasonable walking distance of one. (And when I say "reasonable walking distance," I don't just mean a few blocks. As illustrated in the map above, that's a 3-hour walking round-trip.)
• There are a number of websites and smartphone apps which promise to show the user the locations of charging stations. These services seem to think that users want to be able to locate a nearby charging station, as one would when running out of gasoline or diesel fuel. But because your fuel range is more precious to begin with (it's like having a fuel tank with 1/4 of typical capacity), you'd be foolish to wait until you needed to add charge before you started looking for a recharge. And because refueling takes a serious commitment in time (the public "Level 2" charging stations typically add about 20 miles of range per hour), it requires a some commitment to spontaneously decide to charge. Imagine looking down at your fuel gauge, and thinking, "Oh, I need to find a place to refuel, because I'm down to 10 miles of range. I hope we can find a refueling site within 10 miles (which could take 30 minutes to reach in Los Angeles) and we'll need to find something to do for two and a half hours while we take on enough fuel to get home." When your vehicle is constrained by these parameters, you do NOT put yourself in these situations.
• Of those charging stations that do exist, a significant number are non-operational. Some have been vandalized or accidentally damaged; many have problems communicating with their networks (as with ATM and credit-card transactions, a real-time electronic transaction takes place in order to start and stop the charging process). One station located at a retail location I frequent has been on-again/off-again every time I've visited. 
• A given public charging location has equipment to charge from one to four vehicles (typically one or two). The sales rate of plug-in vehicles has increased far faster than installations of charging locations, so the likelihood of finding an unoccupied charging site decreases daily.
• Even when a municipal sign bearing a local ordinance number prohibits non-electric vehicle parking in a charging space, it's not at all unlikely that an internal combustion engine-powered (ICE) vehicle will be parked in the spot, potentially preventing EVs from proceeding to their next destination. This is known in the EV community as ICEing. Many charging stations aren't marked as EV-only at all. Perhaps worst of all, EV owners occasionally use the charging spaces as parking spaces without charging - a serious breach of etiquette and manners, since many full-electric drivers are depending upon supplementing their charge to complete their journey.
• We established an EV charging account with the Los Angeles Metro Transit Authority, which has EVSEs (Electric Vehicle Supply Equipment, the official term for the hardware that connects your EV to a source of electricity) at some of its mass-transit parking lots. When I reconnoitered the Metro subway station near Universal Studios in Hollywood around 8am one morning, I discovered four EVs charging at the four available charging points at that locale. In all likelihood, those four drivers had gone to work for an 8-hour day, and might well expect to do the same every weekday. So the prospects of anyone else using those charging sites would be dim, or they'd have to engage in a competition for early arrival.
• Even though it might seem logical to locate charging stations close to home, it's probably not that important, if you have your own "fast" Level 2 EVSE installed. In the event that your home charging system fails, it might be helpful to know you can walk two and a half miles home while your car charges, but if you depend upon public charging, you might just as likely end up charging 30 miles from home and having a long lunch there while waiting. 

Here's the problem with the current public EV charging infrastructure: a citizen commuting daily, using almost the entire range of their EV on the way to work, then riding public mass-transit, charging their vehicle during their workday, and finally driving their EV home at night is arguably using their EV to greatest advantage. They're generating lower emissions; lowering fuel costs; and (potentially) reducing use of fossil fuels, etc. But if there's no guarantee of recharging your vehicle before returning home, then it's an impractical or impossible plan. I'm not sure how the owners of those four cars I saw charging at the Metro station make it work - I suspect that they're not actually driving far enough to require a charge at the end of their day. Which would be a breach of etiquette and logic - taking up a charging space for 9 hours when your car only needs 30 minutes of charge (even a fully discharged average EV will be finished charging in 4 hours). Chances are, some of those EV drivers are using the EV-only parking as leverage to have a parking space in these over-capacity public transit parking lots. This is just another problem with having such a thinly populated charging infrastructure.

In the EV community, there are conventions that: a) if you arrive at a charging station and the car connected to the station has completed its charge, you can unplug the cord from the charged car and use the EVSE if you can get the cord to reach your own charging port; and b) if you arrive at a charging station and the adjacent vehicle is still charging, leaving your charging port door open is a message that you'd like the other EV owner to plug the EVSE into your car when they leave. However, these practices are only possible when more than one parking space is within range of the charging station's cord. Only on a few occasions have I seen more than one parking space designated for sharing a vehicle charging station.

(In the case of free chargers - mostly legacy municipal experiments and pilot EV programs from a decade or more ago - the charge will start automatically. In the case of for-pay charging, most charging networks provide smartphone apps through which users can remotely start a charging session. Our Focus Electric also has its own Internet connection, through which we can see if it's plugged in. I'd also be happy to pay to charge someone else's vehicle on our charging account in those rare occasions where I found another unattended EV indicating that it needed a charge at a for-pay EVSE.) 

As an exercise, I've experimentally plotted what it would take to drive our Focus Electric from Los Angeles to Las Vegas - a trip we make regularly for trade shows. In a conventional car, in good traffic, the 270 mile trip can be completed in a little over four hours on a single tank of fuel. To be able to make the trip in our EV, we'd want to arrive at a charging station every 60-70 miles - and that infrastructure almost exists, but for a 150-mile gap in the California desert. At each stop, if there was an available charger (some EV charging apps promise to show whether EVSEs are occupied and functional, but in only a few attempts to use this information, I've experienced very poor accuracy), and we could get our charging network account to work (I've had problems with perhaps 1/3 of the dozen attempts I've made so far), we'd then have to wait for three to four hours before driving the next hour to the next charging site. Assuming we made every charging stop, found the station vacant and charged for 3.5 hours every 60 miles or so, we'd make the "4 hour" drive in about 19 hours. But if any of those chargers were out of service - of the few excursions we've made requiring more than a single charge, one of them required four attempted locations before finding a working charger - we'd never complete the journey. So while installing just one EVSE each in Victorville and Baker, California might make the theoretical chain of required stops, it would hardly count as a kind of fueling network. In my limited experience with public EV charging stations, there's no way that I'd count on that thin an infrastructure being 100% operational, and it could only accommodate a few vehicles traveling in the same direction. 

Despite stories that there are automobile club emergency EV charging trucks which can provide Level 2 roadside charging, it sounds like these "pilot programs" provided a couple of specialized vehicles for each of a few states. I'm not planning my family's security on whether one of a few trucks in California is available at the time.

Public charging stations continue to slowly increase in number, but not at a rate which will improve this situation in the near future. It's still "pioneer days" for EVs, and those of us taking this plunge are constantly reminded of that. Even though my wife's workplace is claiming that they'll eventually be installing six EVSEs, we already know of four EVs that might use them. By the time the equipment is installed, there might be more vehicles than that. When the number of employees at one workplace which are commuting in EVs exceeds the number of charging stations, it would take some cooperative effort and scheduling serendipity to work harmoniously.

PUBLIC CHARGING NOT REQUIRED

My plan for owning and operating a plug-in electric vehicle never depended upon using public stations. I still think it makes perfect sense for us to charge our vehicle at our home and use it primarily within the 35+ mile radius of operation of a single full charge. Owning an EV in a region without any public charging infrastructure could be perfectly workable. As we've owned the Focus Electric and experimented with traveling further than a single charge, we've developed strategies and familiarity with those restrictions. 

Indeed, we haven't felt restricted by having an EV. In fact, we have yet to revert to driving one of our ICE vehicles in three months. Partly, that's because we're willing to academically explore the consequences and compromises of driving trips which require more than a single charge, and because we enjoy the adventure of it. We done about six so such journeys so far. But for the day-to-day vehicular needs of our life, driving all-electric has been easy and fun.

How Do I Charge My EV?

FUELING EVS

Charging electric vehicles is a very different proposition from tanking up with liquid hydrocarbons. When we fill up on gasoline or diesel fuel, we use the product of thousands of hours of sunlight which fell on hundreds of square feet of plants, hundreds of millions of years ago. We transfer the potential energy to propel the vehicle and its occupants hundreds of miles at more than a mile a minute in a matter of seconds in a refined form of this petroleum. Through the magical process of photosynthesis (upon which pretty much all life depends), plants capture a tiny proportion of our sun's total light energy and store it in molecules they make from water, carbon dioxide and a smattering of other compounds. The natural process of plants decomposing to petroleum over vast periods of time is a battery of sorts, which takes millions of years (plus no small amount of human time and energy to extract, transport and refine) to store, but releases useful amounts of its stored molecular energy on demand when we press on the throttle pedal. Modern electric batteries can be thought of as faster than fossil fuel storage, in that they can store energy in minutes, rather than the millions of years to yield "fossil fuels." But since the Industrial Revolution, we humans have become both accustomed to the convenience and fantastic energy density of these energy sources upon which much of our civilization depends. We take for granted that the "liquid sunshine" through which we've been burning is for all practical purposes a one-time resource (for our species, anyway) and an effectively finite one. Regardless of how much crude oil there is left on the planet, when it's gone, it'll take a couple of hundred million years to make another batch - and our own molecules will be part of that batch. 

Today, we have a highly developed civil infrastructure which produces and distributes electricity to wherever humans need it. The electricity might come from any number of sources, including combustion of those plant-based fossil fuels, the releasing of the atomic bonds formed at the beginning of time in nuclear reactors, and "renewable" sources such as photovoltaic, wind, hydroelectric and wave power. When we tap into this ubiquitous electrical network and store its potential in a modern electric car battery, the process is limited by the electrochemical nature of batteries. Most contemporary EVs use lithium-ion and lithium-polymer batteries, the same technologies which are currently favored to power our mobile communication and computing devices. These battery technologies offer the most economical balance of duration and power performance to volume and weight, while offering improved charging performance (lower times) over prior technologies. However, charging batteries currently takes far more time than traditional liquid refueling.

(Find out what sources are used to produce the electricity at your location with the Environmental Protection Agency's "How clean is the energy I use?" website.)

CHARGING EQUIPMENT

Current EV vehicles actually incorporate the charging hardware in the vehicle, as the charging process is meticulously and intimately interactive between the charging circuitry and the battery system. This is practiced to protect the extremely valuable battery (which may represent more than half of the value of the vehicle) from range and lifespan damage due to electrical load and thermal extremes. All electrochemical batteries are affected by extremes in temperature, and electric vehicles can expect to be operated in the full range of temperature extremes, although range will be adversely affected in very cold and very hot conditions. Many vehicles, including our Focus Electric, both heat and cool the battery pack to optimal temperatures during charging and discharging to maximize both their range and their lifespan. EV manufacturers also limit the charging and discharging thresholds of the batteries during user operation to considerably less than the batteries' ultimate limits. I've read that the Chevrolet Volt pack discharges to only 30 per cent of its capacity, and I think most packs stop charging well short of 100 per cent. So while it might be possible for current EVs to have markedly longer ranges than they do (on a brand-new battery), manufacturers deliberately software-limit the stress on batteries to extend and ensure their warrantied service life.

Since the "charger" is actually built into the EV, it's considered incorrect to refer to the hardware used to connect the vehicle to an electrical supply as a "charger." The official term for this device is the awkward acronym "EVSE," for "Electric Vehicle Supply Equipment." However, the community seems to accept "charging station" as an expression to refer to both home and public/commercial EVSEs. 

IS IT AS EASY AS PUMPING GAS?

Easier. Plug in the cable from the EVSE, and the car starts charging. When it's done, it will automatically stop. Whenever you unplug the cable, the charging automatically stops.

HOW DO I USE FOR-PAY EV CHARGING?

In our limited experience with using paid charging stations, we've used only two networks: ChargePoint and Blink. These two companies predominate in the Los Angeles area. 

Both services provide customers with methods for paying via monthly account or on a per-use basis. They have provisions for "guest" use, so any EV owner can walk up to a public EVSE, call a phone number on the EVSE, give a credit card number to a live operator, and they will remotely authorize the EVSE to begin charging your vehicle.

By establishing accounts with these charging networks, you get discounted charging rates, and the convenience of initiating a charging session by simply waving an RFID card by the EVSE. Rates vary, and are set by station owners, but range from similar to our home electrical rates to three times as much. Even at the highest rates, it's less expensive than gasoline, and we have so infrequently used pay public charging that it's not an issue for us.

UPDATE 2/16/14: I previously neglected to mention that some for-pay charging stations charge the user by the hour - even after the car completes charging. I think this is fair - they're trying to incentivize users to move on and make the station available for another EV user, and protecting their ability to generate revenue.

FREE ELECTRICITY?

There are many charging stations out there there are free to use. Most of these are municipally supported - almost every town has at least one free charging station at their city hall, apparently installed as part of an "initiative" for some purpose or another. Some of these are over a decade old, and not compatible with modern mass-produced EVs. Some have been converted to the modern J1772 connector.

Most car dealerships for brands (Nissan, Chevrolet, Ford, Fiat, etc.) that sell EVs have publicly-accessible EVSEs on their lots. We've never used one, but we've been with friends using one of two parking-lot stations in a Nissan dealership for their Leaf, and our Ford dealer's EVSE is in a terrible location partially blocking a driveway through their service area. Between those two examples, I think we can extrapolate that a dealership is not going to be the best choice for charging. I've heard of people having the chutzpah to ask to charge their differently-branded EV and being begrudgingly allowed to use them. I've also seen something about "priority to (brand name)" somewhere on the Web, so some dealerships actually have established a policy to charge off-brand EVs.

WHAT DO EVSEs DO?

If they're not doing the charging, what do EVSEs do? They provide a safe interface between the electrical supply and the charging port on the vehicle. That is, the EVSE does not energize the plug electrically until it is certain that it is connected to an electric vehicle. Users of electric vehicles would be expected to charge them in all environments (i.e., standing in the pouring rain), and EVSEs are often located where they can be accessed by small children, so their functionality must NOT be that of a 240 volt extension cord.

In addition to incorporating ground fault interrupt circuitry to help prevent electric shock to users, EVSEs only energize the conductors on their connectors when they have established communication with an EV, and interrupt power when they detect that the connection has been broken. EVSEs can even anticipate when the connection is about to be broken with switches built into plug latch mechanisms. This prevents potentially dangerous and destructive arcing from unplugging a very high current load connection at as much as twice the 120 volts with which most citizens are familiar.

EVSEs also report the amount of current which they can provide to the vehicle. The vehicle should then only begin charging at a current at or below the EVSE's advertised rate.

Our Aerovironment Level 2 EVSE

ELECTRICAL CONCEPTS

Here are some basic electrical concepts that the EV owner may encounter regarding charging equipment:

• The unit of measure of electrical difference of potential is a volt, abbreviated with the letter "V," as in "240V." The higher the voltage, the easier it is for electrons to flow past conductive impediments, or resistance.
• Typical household outlets are 120 volts. Some appliances, such as all-electric clothes dryers, stovetop ranges, ovens and air conditioners are designed to run on 240 volts, and will use plugs and outlets that are incompatible with 120V outlets. 
• The unit of measure of electrical current is the ampere, also called the amp for short, and abbreviated with the letter "A," as in "30A," meaning "30 amperes." The higher the amperage, the more work can be done by that electrical source. 
• Typical household outlets and the wires to them are designed to safely convey about 15 amps of current. If that current is exceeded by more than the safe level (like plugging the waffle iron and toaster into the same circuit), then a fuse or circuit breaker designed to limit the current to 15A will interrupt the circuit before the wires inside the walls get dangerously hot from exceeding their designed maximum load of (in this case) 15 or more amps. 
• Some appliances may require higher currents of 20 to 50 or more amps of current. These will utilize special plugs, preventing the higher-current device from being plugged into an outlet with inadequate supply. Some outlets and plugs are designed so that lower-current devices can also be utilized in outlets designed for higher-current devices of the same voltage.
• Circuit breakers are a protection mechanism to prevent wiring and connectors inside the structure from dangerously overheating due to overload. The current rating (in amps) of the circuit breakers is chosen to suit the expected load from connected electrical devices, and the total load of all the circuit breakers is chosen not to exceed the available current from the wiring supplied by the utility company to the circuit breaker panel. From the circuit breakers, wires designed to conduct a specific maximum current are routed to one or more locations, where they are terminated by either an electrical outlet, or a permanently-wired device.
• Supply refers to the electricity which flows from utility company infrastructure to the customer's site, through a circuit overload protection mechanism (fuses or circuit breakers), and to the outlets and devices which require electrical power.
• A device's rated operating current should never exceed the current rating of its electrical supply. So a 12A appliance is fine in a 15A circuit. So are three 4A devices. A 10A toaster and an 11A microwave oven in one outlet, totaling 21 amps, is NOT appropriate and should cause a 15A circuit breaker to "trip" in order to protect the 15-amp rated wiring and connectors.
• An electrical supply's current rating can and should exceed the loads placed on that circuit by the total current draw of all devices on that circuit. For example: It is OK to plug either a 1A, 10A, or 25A device into a circuit properly wired to supply 40 amps. It is also OK to plug all three, totaling 36 amps. Having a higher-rated supply circuit (that has been properly installed for its advertised amperage) than the expected device's rated load is typical and desirable: when you turn a single 60 watt porch light on, that represents a 0.5A load on what is likely a 15A circuit.

CHARGING STANDARDS

There are currently a handful of EV charging standards. These are characterized by: 1) the voltage and current requirements of the charging equipment; 2) the rate at which the given charging system adds charge to the vehicle's battery; and 3) the kinds of physical connectors used to connect the charging equipment to the vehicle. Most contemporary EVs have flexible charging systems that can electrical supply from a range of available supplies. These systems often automatically adapt to the available power supply.

The charging standards most commonly encountered by EV users today include:

• Level 1 - Uses the SAE J1772 connector on both the vehicle and the charging equipment. Plugs into common household 120 volt AC outlets, and draws less than 16 amps. While this allows users to plug their cars into existing outlets found anywhere, charging is extremely slow. In the case of our Ford Focus Electric, Level 1 charging adds about 4 miles of range per hour, so a fully depleted battery pack might take as more than 20 hours to replenish at this rate. Most vehicles are sold with Level 1 chargers included. Despite the apparently slow charging, it's a good thing to have with you at all times. We visited friends recently who live far enough away that we required an additional 30 miles of charge to return home. But because we were parked at their house for more than 7.5 hours, an extension cord across their yard was adequate.
• Level 2 - Uses the SAE J1772 connector. Using 240 volt AC sources up to 200 amps (typical home Level 2 EVSEs range from 20 to 60 amps), this is also sometimes referred to as a "fast charger." Charging rates/times vary. In the case of our Focus Electric, our home L2 EVSE and commercial L2 stations add about 20 miles per hour of charging. All of the for-pay charging stations we've encountered so far were Level 2.
• DC Fast Charging - Uses the CHAdeMO connector. This infrastructure promises charging rates which close the gap to traditional liquid hydrocarbon fueling. The Chevrolet Spark EV, Mitsubishi i-MiEV and some models of Nissan Leaf are equipped with connectors for this very fast charging standard. (Tesla Motors is currently taking pre-orders for a $1,000 CHAdeMO adapter for their Supercharger-equipped Model S. Non-Supercharger Model Ses will require an additional $1,900 upgrade.) Most CHAdeMO-equipped EVs claim that the 480 volt DC charging system can charge a fully depleted battery pack to 80 per cent capacity in about 30 minutes, providing 60 to 70 miles of range (Tesla claims 150 miles in an hour). This is still far less than the 300-600 miles of range a gasoline or diesel vehicle can add during a 5-minute refueling stop, but makes far more practical the notion of a trip which requires multiple full charges, where each 1 hour/60 mile drive would be followed by a 30 minute charge (our Focus Electric requires a 3.5 hour charge to replenish each 1hr/60mi driving stint). Nissan warns that DC Fast Charging may significantly affect the long-term range performance of the battery pack, indicating a deleterious effect of this charging system upon batteries. For 36-month leasees, this isn't as much of a concern, but for purchasers of EVs, this might give pause. In any case, CHAdeMO charging stations are very rare, even in the Pacific Northwest where the standard has had the highest distribution. I considered this as attribute while we were shopping, and when I realized how unlikely it was that we'd actually encounter a CHAdeMO station, I excluded that consideration.
• Tesla Motors - EV manufacturer Tesla Motors chose to establish their own proprietary connector standard, rather than adopt the widely-used SAE J1772 connector (they make adapters to most of the other connector standards available for purchase). But since 2012, Tesla has sold over 20,000 Model S in the United States, and projects 30,000 more sales in 2014, so they may not have needed to conform to the widespread standards. Because the Model S' optional 85kWh battery pack is far larger than every other EV (giving the Model S three to four times the range of other EVs), but it uses a similar amount of power during operation, the rate of miles of charge over time is similar (effectively depending upon driving style), but replenishing the full pack on slower systems can take a long time. Tesla maintains and is expanding its own network of Supercharger DC fast charge stations, which can add 120 miles of range to their 85 kWh Model S in 20 minutes, or 200 miles in 30 minutes. Tesla's intentions are to provide owners of their premium EV an infrastructure for traveling longer distances with similar ease to traditional internal-combustion refueling. As of 2013, Tesla announced their intention to make each of their Supercharger Stations into a "battery swapping" station, where owners could pay to borrow a charged battery pack, which could be changed in as little as 90 seconds. Tesla also claims that by Winter 2013, they will have established a "coast to coast travel" network - but I suspect that this reaching one point on each coast, so you might still end up 1,000 miles short of your destination. 

CHARGING RATE DOES MATTER

While charging an EV battery is many times slower than replenishing gasoline or diesel fuel, it provides practical fueling times for many situations. At the typical Level 2 charging rate of 20 miles per hour, a typical 8-hour workday or sleeping period is enough to recharge the batteries of those EVs whose ranges are 100 miles and under (8 hours x 20 miles of charge/hour = 160 miles). 

But it's important to consider available charging rates together with expected driving habits.

For some EV owners, there may be little incentive for spending potentially thousands of dollars to install a Level 2 EVSE. Though a Level 1 EVSE may charge slowly at 4 miles/hour, if your commute is 20 miles round-trip, you only need 5 hours of L1 charging to compensate for that. It could be perfectly economical and acceptable to charge only with the L1 EVSE.

At the other end of the spectrum, the fastest available charging might seem like a way to travel beyond the range of a single battery charge. However, even 20 mile/hour charging rates of typical L2 public charging stations create awkward delays in travel. Pausing at a charging station for 90 minutes to gather 30 miles of additional range to complete the day's travel may not coincide with a productive or safe location for spending 90 minutes. It's possible to do - we've been scheduling meal stops within walking distance of charging locations before we set out on trips which exceed a single battery charge. But it's an awkward process, and finding an occupied, faulty or even missing EVSE at your planned stop can sabotage the plan and the trip. Many owners won't be exploring the world past the range of their EV's battery, but we've been deliberately making that part of our ownership experience. While it feels like Pioneer Days for EV owners, you can make it work with some preplanning and a willingness to take longer trips at a, uh, leisurely pace.

The Tesla Model S and those few vehicles with DC Fast Charging can charge much more quickly, but the networks of public charging stations supporting them is even smaller than the thinly-distributed Level 2 stations that predominate. The difference with these fastest charging technologies is that an EV owner might be willing to wait 30 minutes to collect 60 miles of charge, while 3 hours (at L2) would be intolerable. But one might have to drive 30 miles out of the way to find stations that support these fastest standards. (Some members of the EV community - including Tesla Model S owners - make their home EVSEs available for use by sharing their location on sites like PlugShare.)

SO DO I NEED A FASTER CHARGING SOLUTION?

Maybe not. The answer for you is based upon several factors:

• How much power you will use for your commute.
• How fast your vehicle can charge (which is a combination of your vehicle's charging system and the current that a given location's EVSE provides).
• How long your vehicle will be stationary at an charging source. 
• Whether you want your vehicle to be charged as soon as possible, for unexpected transportation needs, or are prepared to potentially leave the vehicle charging until shortly before the next schedule departure time.

Here are simple formulas for visualizing what kind of charging schedule you can expect from a given set of these parameters:

[Miles depleted from battery] / [EVSE miles of charge per hour] = [hours to complete charge]

[hours to complete charge] + [arrival time @ EVSE] = [charge completion time]

So for example, if your drive to work is 22 miles one-way, then a round-trip would cover 44 miles. If the Level 1, 120 volt, 15 amp EVSE which came with your car charges at a rate of roughly 4 miles per hour, and you arrive home at 6:30pm (18:30), then:

44 miles / 4 miles chg per hr = 11.0 hrs (11 hrs, 0 mins)

11:00 + 18:30 = 5:30am charge complete

While the same trip with a 20 mile per hour Level 2 EVSE results in these figures:

44 miles / 20 miles chg per hr = 2.2 hrs (2 hrs, 12 mins)

2:12 + 18:30 = 8:42pm charge complete

In the real world of EV driving, the actual impact of driving even the exact same route can affect battery depletion and thus charging times by more than 30 per cent, so some actual driving tests would be necessary before committing to a charging solution.

PUBLIC CHARGING - IT WORKS, BUT . . .

Perhaps some day, every parking spot will automatically charge our cars inductively. But for now, for-pay commercial and free public EVSEs are somewhat sparsely distributed, even here in Southern California.

The most significant function of public charging stations is that they provide the only practical way to travel to destinations beyond the range of your EV's battery. But because public charging infrastructure is rather thinly distributed, one must be careful to plan alternate charging locations in case EVSEs at proposed stops are either occupied or non-functioning. We've made several trips beyond single-charge range in our first months of EV ownership, and we've had to make use of contingency plans a number of times when public charging stations turned out to be broken or already engaged with another EV.

For more, see my post, Why public EV charging stations might not be as useful as you think.

ROUGHING IT

In the days before automobile manufacturers began producing EVs, hobbyists charged their home-built electrics from household circuits, including not only typical 15A, 120V services, but the higher-powered service sometimes installed in homes to supply power to appliances like electric clothes dryers and ovens. 

So can these circuits - which sometimes have the 240 volt, 30+ amp service required for Level 2 charging - be used for fast charging an EV? Can you take your L2 EVSE along with you and plug it into the dryer outlet in your grandma's house? Maybe. 

While modern EVs typically come with a Level 1 EVSE which can plug into any household outlet, it's almost never going to be convenient to charge for the 20+ hours it might take to recharge your fully-depleted battery pack after 75 miles of driving (in the case of the largest battery pack in a Tesla Model S, you could spend 90+ hours after driving 300+ miles).

It's possible to plug a Level 2 EVSE into some of these existing outlets, but it's a non-trivial pursuit. There are many standards of outlets and plugs, some having bearing subtle differences which both identify them and prevent inappropriate connections between devices and electrical service. If you happen to be the adventurous sort who has a reason to periodically travel well beyond the range of your battery and know that a home or business owner somewhere along the route won't mind you using their electricity (and possibly unplugging their oven, and parking on their grass so the cable will reach through the kitchen window), it's possible to take along your L2 EVSE (provided it has a plug for 240 volt power - some are designed to be wired permanently) and the appropriate adapters (no home or business is likely to have the outlet type which is physically compatible with your EVSE's plug), and charge fast enough that you don't have spend the night (or more) before returning home.

Me, I'm enough of a geek that I've been scheming about making trips requiring several full charges. This involves almost 80 per cent of the trip time spent charging, and 20 per cent in motion. So traveling 300 miles could take more than 20 hours - IF you make it to the charging stations, AND they are available and operational. If we do this, one of the options for fast charging is plugging our L2 EVSE into a 50 amp, 240 volt service in a campground. So that's one of the adapters I'll have in our kit.

CONCLUSIONS

Most owners of EVs with 80 miles of range probably rarely use charging infrastructure away from home. Indeed, the point is that most automobile owners drive far less than 80 miles per day. If you fit in this profile, you may not need to concern yourself with charging away from home.

If you're lucky enough to have a charging stations at your destination, you might be one of the very few who can travel nearly the full range of your EV's battery in both directions. But if you drive more than half of your range, the charging system at your destination must be available and functional, or you'll either be stranded or looking for a public charging station that's within whatever remaining range your EV's battery has.

If you live in a region with public charging stations, that provides some flexibility to the kinds of travel you might undertake. But the availability and operational status of public stations is unpredictable at this point in time, so you must be prepared with contingency charging locations which are within range, and the effect that this will have on your schedule.