Sunday, September 14, 2014

Electric Air Conditioning Technology Benefits

Japanese industrial manufacturing giant DENSO debuted a new electrically-powered air conditioning compressor in the Ford Focus Electric in 2012.

Mid-September can be toasty in SoCal

During our first summer of owning a 2013 Focus Electric, the benefits of having a variable-load A/C compressor in terms of energy use have become noticeable as I've observed the Focus Electric's user-configurable Climate energy use display. On days like today, when air temperatures on the asphalt here in Los Angeles exceed 110°F, the Climate gauge peaks at over 4 kilowatts of power when I first turn on the cooling in the hot car. But after running for only 5 to 10 minutes, I can maintain a comfortable cabin (at least in the front seats, with the A/C ducts blowing cool air directly on us) by eventually dropping the fan to its lowest speed - where the display indicates that the Climate system is consuming well under 1.0 kW. In the past, A/C compressors were not variable-load. They were on or off, and temperatures were either modulated by duty-cycling the compressor with an electrically-activated clutch, or by mixing engine coolant-heated air.

Just after entering the Focus Electric in 110°F temps, the Climate system works hard to cool the cabin, using nearly 5 kW. But within minutes, the HVAC system can maintain comfortable temps at under 1 kW.

wrote previously that I do NOT use the automatic thermostat in our Focus Electric in hot weather, leaving the temperature set to "LO" to avoid the HVAC system activating its high-wattage heater to regulate the amount of cooling. I've practiced that for this entire summer, and the strategy works, except that sometimes it gets too cold when temps are merely "very warm" (85-90F), and even pointing the vents away from passengers and turning the fan all the way down doesn't moderate the cooling enough. This demonstrates how effective and impressive the DENSO-based A/C is, but how Ford still should have some way to regulate cooling without turning on its 6+ kW heater. When it's 82F outside and muggy, running the A/C at "LO" will make it really cold inside, and turning the A/C switch OFF results in immediately sticky conditions in the cabin.

And as we head into winter, I'm reminded that the Defrost system appears to run both A/C compressor and heater to clear the windows. This is a typical strategy of all cars, but because the Focus Electric's cabin heater is electrically-powered, and uses a devastating amount of power (while heat in traditional cars is scavenged from the engine cooling system), a driver has no choice but to run the range-sapping defroster in order to maintain fog-free window interiors for safety.

So bravo to DENSO for what appears to be a superb solution for efficiently compressing refrigerant with electricity. I've been able to maintain the same 245 Watt-hours/mile consumption rate that I'd averaged in the winter and spring months before hot weather arrived. I've read that electric A/C compressors are a trend among all motor vehicles, and I'm encouraged by our own experiences.

Tuesday, September 9, 2014

Test Drive an EV Next Week!

September 15-21 is National Drive Electric Week, organized in part by Plug-in America, The Sierra Club, and the Electric Auto Association, and partially sponsored by Nissan.

Events will take place around the U.S. - this search engine promises to locate NDEW events by zip code.

If you live in Southern California, the City of Santa Monica will host the 9th Annual AltCar Expo, where many manufacturers of alternatively fueled (electric, natural gas, hydrogen, etc.) vehicles provide free test-drives to attendees. We attended this event in 2012 and 2013, driving most of the available (and not-so-available, like the exotic, rare and lease-only Honda Clarity hydrogen fuel-cell car) electric, plug-in electric, compressed natural gas (CNG) and fuel-cell vehicles before deciding to lease a Ford Focus Electric last October.

Tuesday, September 2, 2014

Blink Network Introduces Kilowatt-Hour Pricing & Reduced Time-Based Increments

Today, I got an email from CarCharging, the new owner of Blink Network, announcing a change in pricing structure on September 2, 2014 for charging electric vehicles. In "states where such pricing models are permitted" (CA, CO, FL, HA, IL, MD, MN, NY, OR, UT, VA and DC), CarCharging says:
Fees for Level 2 EV charging stations owned by Blink and operated on the Blink Network in the kWh eligible states will range from $0.39 to $0.79 per kWh, depending on the state and individual’s membership status. Fees for DCFC chargers owned by Blink and operated on the Blink Network in the eligible states will range from $0.49 to $0.69 per kWh, depending on the state and individual’s membership status.
Blink's previous pricing schemes sometimes charged the user for hours connected, even after charging had completed. This was a useful strategy to discourage the use of EVSE stations as private parking for EV owner, and to encourage turnover so that more EV owners could have access.

While we have grumbled a few times about paying far more than the a fair price for charging because our parking stay continued hours after charging completed, I think I'd actually rather have the old system that provided a likelier opportunity for any arriving EV owner to take on charge by applying pressure on users to move on after charge completion. I'm really tired of finding EVs (mostly Tesla Model S) using spaces marked "Electric Vehicle Charging ONLY" as private parking spaces, without even the effort of connecting a charging cord. For those of us attempting to make a go of electric-only vehicles, use of public charging is NOT about parking privileges.

10/2/2014 CarCharging's announcement of Blink Network pricing changes

Monday, August 25, 2014

"Car & Driver" magazine: "Assault on Battery - Three Early Hybrid Energy Storage Fears That Never Materialized"

While thumbing through my backlog of unread automotive periodicals, I discovered this article from the June 2013 issue of Car & Driver. I appreciate the selection if topic, not just as a an EV owner, but because the popular media often fails to follow up on their own predictions about anything.

Car & Driver, June 2013 "Assault on Battery - Three Early Hybrid Energy Storage Fears That Never Materialized"

Friday, May 23, 2014

Will an EV Fit Our Driving Lifestyle?

We find that in discussions with acquaintances about the subject of EV ownership that the most common reservation about ownership of the current crop of EVs offering ranges of 75 to 80 miles is, "Yes, but what if I suddenly decide to . . ."  In nearly every case, these comments have been made by individuals who have absolutely rigid daily schedules with invariable driving routes, and are the least impulsive of characters.

I, on the other hand, am known to set off on a mission with little to no notice.

And yet, after seven and a half months of EV ownership, we have yet to jump in one of our gasoline-powered vehicles because a trip exceeds the range of our Focus Electric.

To be fair, we're trying harder than most to make the EV work. To that end, we're sometimes defining our itinerary by the requirements of recharging on the road. If we were driving a hydrocarbon-fueled car, some of those trips would have been different, and a few would have taken significantly less time due to fueling (charging). We're treating this EV ownership as a learning adventure, and so it's interesting and fulfilling to go through these new experiences. But we're actually doing more exploring than we would have before owning the EV; driving more often, and further from home than we typically would, just to see how bad it is.

And you know? It's not bad at all.

Sure, once our round trip exceeds 70 miles, it takes some extra thinking (which I find fun, but many wouldn't). When it's a LOT further - approaching two full battery charges, we look for excuses to spend the hours charging doing something useful or fun in proximity to the charging site. Did we do this before owning an EV? No. But the point is that rather than Cramping Our Style, our EV has encouraged us to explore its limits. We haven't called AAA to tow us to a charging site. And we've never gotten caught out so that we end up sitting in our car waiting for enough charge to get to our next waypoint.

So what's the takeaway?

When we were deciding whether an EV would fit our lifestyle, I discovered that we'd only driven our daily driver about 5,000 miles during the previous 12 months. As it stands right now, we're on track to put about 8,000 miles on the Focus Electric every 12 months. That's how enthusiastically we've been using it.

Living in Los Angeles, round-trip distances to points of interest can certainly challenge even two full charges (160 miles) of our Focus Electric. And yet we've never resorted to another form of intra-city transport since getting an EV. 

As I've written previously, the current state of public charging infrastructure is such that it's unlikely to be truly useful to most people. But I think the 80 mile typical range of a single, daily EV charge suits the majority of drivers. For anyone with a predictable itinerary under 60 miles per day (many sources claim the average daily U.S. commute is 32 miles, and I'm allowing for impromptu side trips), the cost of operation and ease of use make an EV a perfectly serviceable second car (we actually think of our EV as our primary vehicle, and our small motorhome as a secondary vehicle for even short- and medium-distance adventures).

Thursday, May 22, 2014

Avoid Automatic Temperature Control to Minimize Range Impact from Air Conditioning in a Ford Focus Electric

It’s now May 2014, and we’re entering our 7th month of leasing a 2013 Ford Focus Electric. Here in Southern California, we’re having a hot spell, with temps touching 100 degrees, and thus we enter a new phase of our experiment that is EV Ownership: hot weather operation.

Not having an internal combustion engine (ICE) from which to utilize waste heat, the Ford Focus Electric (FFE) uses power from its main 325 volt, 23 kilowatt-hour lithium-ion propulsion battery to power what is obviously some kind of electrical resistance heater, probably not unlike the glowing wires in your toaster or hair dryer. Based upon my observations and crude calculations (using data from the FFE’s own range-estimating battery gauge), the heater uses electricity at a rate of around 6,000 watts - about the same as the typical household electric oven, and what I'm guessing the FFE requires to move through the air at 30 mph. This has a devastating impact upon vehicle range. The FFE has a nominal range of 80 miles or so (potentially going over 120 miles in low-speed, stop-and-go traffic, or only 60-65 miles at 65 mph on a hilly road). If the heater were powered for the duration of a full-battery trip, its total range would be reduced by about 30% - dropping the range from 80 miles to around 56. Yikes.

I’m sure we’re not the only EV users who choose to wear warm clothes and make do with our seat heaters whenever possible. We live in Los Angeles, and our mild local weather played a part in our decision to take the EV plunge. I probably wouldn’t have "gone electric" if we lived in the FFE’s home state of Michigan. Between low-temperature battery efficiency loss and having no choice but to run the heater, I wouldn’t be surprised to lose half of the Focus’ range in truly cold climes. But SoCal winters rarely reach the 30s, so that’s not an issue.
In my early experiments with the FFE’s HVAC (Heating, Ventilation and Air Conditioning) system, I was as struck by the apparently small range impact of the A/C system as I was by the traumatically high burden of heating the cabin. This is particularly impressive, since the FFE has an electrically-powered refrigerant compressor, and because A/C compressor load has historically been a significant contributor to energy use, even in conventionally-powered automobiles. (Since writing this, I’ve read that electric A/C compressors are a trend in automobiles in general, so they apparently provide some efficiency benefits.) Furthermore, the Focus Electric’s A/C system is fairly effective, maintaining a comfortable cabin even during an hour of 100 degree driving, despite bright California sunshine and the FFE’s generous greenhouse.

Doing experiments today in 98 degree weather, I observed a 10.7% reduction in estimated range by engaging the A/C and selecting “LO” temperature (the HVAC system never stops cooling at this setting). But as I raised the target temperature on the HVAC system until it exceeded what was the apparently the cabin's current temperature (at 71° F), the battery range dropped precipitously (see graphic below), reducing range by over 26%. Obviously, the system was engaging its electric heater to modulate the HVAC temperature.

In an internal-combustion vehicle, with its vast supply of free waste heat, mixing in warm air with dry, refrigerated air to adjust temperature is a practical approach (though running a compressor full-time does impact fuel use and vehicle emissions). But in the range-challenged world of BEVs (Battery Electric Vehicles), it is decidedly NOT practical.

I appreciate that the Focus Electric is a “conversion” of sorts - that is, it’s not a ground-up design of a vehicle intended to run on electric propulsion alone. Ford obviously makes and sells only enough of these to fulfill federal mandates or incentives (only a few thousand have been produced in two years), and their decision to engineer a BEV based upon their successful and mature Focus platform is sound (Ford proudly mentions that Focus Electrics are built amongst their fossil fuel-burning siblings on the same production lines in Wayne, Michigan). I accept that like some of the other adaptations of existing platforms, there are compromises that manufacturers and users have to accept: the cargo area is severely diminished by battery pack; just maintaining a fog-free windshield costs 30% of the vehicle’s range; and vehicle dynamics reveal that Ford didn’t engineer the Focus Electric’s suspension for that added 600-odd pounds of battery.
(I’m a harsh critic of any product in general, and automobiles is a lifelong hobby, so I’m particularly picky about vehicle design and performance. But though I sound negative, the Ford Focus Electric is generally a dandy car, and we enjoy using it daily.)
But having the energy-sapping 6 kW heater turn on in a BEV when it’s 100 degrees outside is absurd. Perhaps there’s some reason they don’t want to cycle the electric refrigerant compressor off and on, as conventional auto A/C compressors did for decades. Perhaps the sensibility of the designers is to always provide low-humidity cabin air, regardless of outside temperatures. Many contemporary automobiles run their A/C compressors full-time, mechanically routing some or all of the dehumidified “conditioned” air through the engine-coolant heater core as necessary to supply the cabin with desired air temperatures. But this is an electric car, and it’s already a hard sell to convince the public to buy automobiles with 1/4 of the range of their existing vehicle, and which takes hours instead of minutes to refuel. Further crippling the range of the vehicle in hot weather (and most chemical batteries neither like being hot nor cold) because the heater is employed to counter the A/C system's cooling - that’s just asinine. And although the gas-engined Focuses probably use warm-air blending in their HVAC systems - and the FFE has no doubt inherited much of that system - Ford probably had to design and manufacture an electric heater which surely didn’t exist in the conventional Focus. So they must have had the opportunity to configure the control systems not to energize the heater when in “A/C” mode.

In the last few days, I’ve discovered that operating the Focus Electric’s air conditioning system in high-90s weather and bright sunshine results in: 1) a comfortable cabin environment; and 2) the HVAC system’s apparent inability to reduce cabin temperatures much beyond that comfortable temperature. So while it appears that the target temperature on the HVAC system can be set to a typical temperature: say, 72 or 74 degrees, with the attendant 11% range loss in 100-degree conditions - the reality is that if the outdoor temperature then drops to, say, 85 degrees, the A/C system is then able to achieve those target temps. At the point at which the target temp is achieved, the FFE turns on its heater to maintain that target, as evidenced by a sudden reduction in estimated range. So ironically, the energy consumption for cooling the cabin in the hottest weather is far lower than if the temperatures are cooler (if the HVAC system is allowed to automatically control the temperature).

My strategy for minimizing energy usage while cooling the cabin is simply never to set a target temperature. I set the HVAC target temperature to the “LO” minimum setting, and adjust the cabin temp by adjusting the fan speed, Recirculation mode and vent openings. This prevents the system from ever reaching a target temp and energizing the heater.
  • If it gets too cool:
    • Decrease HVAC fan speed
    • Re-aim the vents away from occupants
    • Close vents partially or completely
    • Turn the Recirculation mode off, so that the system uses warmer outside air
  • If it gets too warm:
    • Open vents and aim more directly at occupants
    • Increase HVAC fan speed
    • Turn Recirculation mode on, so that the system ingests pre-cooled cabin air
Manually turning the A/C mode switch off and on when the cabin feels too warm or cool, like automobile HVAC thermostats of days past, will also work. This will use the least energy short of using no refrigeration at all. But this is a very inconvenient and invasive way to operate the vehicle.
(NOTE: It’s important to also set the temperature target to “LO” when simply ventilating without running the A/C system, for the same reason. If for any reason the HVAC system measures the cabin temperature as being lower than the requested temperature - i.e., the air cools as the sun sets - it wil energize the heater. Again, in internal-combustion cars, this warming of air is essentially free. But in an EV, this shouldn’t be the automatic behavior of the HVAC system.)

I find this all more than a little disappointing. This is the first vehicle we've ever owned that had a fully "automatic" HVAC system, allowing the left and right cabin occupants to simply pick a temperature and ignore the system, which then provides comfortable temperatures by whatever means necessary. But since the system is hardly energy-efficient or well-designed for EV use, I'm unlikely to ever engage the automatic feature.

Some of the inefficiency of internal-combustion engines (ICE) results in constant waste heat emitted from the cooling radiators and exhaust pipes of those vehicles. Our Focus Electric's cost of operation is a fraction of a similar ICE vehicles, partly because its systems suffer less thermal loss. However, having to then generate cabin heat for occupant comfort and safety becomes an energy burden which must be accounted for and borne by the same economically- and dimensionally-limited electro-chemical batteries which currently constrain EV range and refueling time.

In this particular case of the Ford Focus Electric, I think a lot of improvement might be gained by minor software and hardware changes. If I could, I'd just disable the electrical heater in the summer altogether (although I think it may be involved in battery pack heating and cooling, which probably takes place year-round).

I recently read in an online forum of Focus Electric users that some anomalous behavior of the HVAC system (sometimes powering up with the blower in full blast, always turning on the A/C mode with the fan, etc.) could be remedied by rebooting the car's infamous MyFord Touch system. This suggests that perhaps the “heater with A/C” behavior about which I’m ranting here is under software (designed by Ford, and running on the Microsoft Auto operating system) control. So there’s some possibility - even hope? - that the behavior could be changed - or at least made user-optional - by a future firmware upgrade. Yeah, right.

I'd like to think that purpose-built electric vehicles might incorporate better ideas about scavenging and routing the inevitable waste heat created in the vehicle's energy and propulsion systems, keeping them in thermal reservoirs for use in cabin climate, and generating additional heat as economically as possible. In our Focus Electric, simply attempting to prevent the windshield from fogging in cold weather - a safety-related issue - requires energizing the monstrous battery-zapping heater. Ideally, there should be a very low-power defogging heater which can run constantly in these conditions.

Carrying around stored electrical energy for automobile propulsion remains a challenge in search of a solution. Although the Tesla Model S would appear to have achieved something with a claimed 300 mile range, it's 85 kilowatt-hour battery contributes substantially to its $90,000+ price (which may not be profitable) and certainly to the car's massive 4,700 pounds. And while the Model S has a range which sounds similar to a fossil-fueled car, even its proprietary, semi-exotic and rare Supercharger charging stations take 30 minutes to add 170 miles of range. Use existing public charging infrastructure to recharge your Tesla Model S, and it takes the same 20 miles/hour as most other EVs - not even remotely like a gas-station fill-up. If future battery solutions provide similar range at a fraction of the cost and half the weight and volume, having a comfortable cabin in an EV will cease to be an extravagance.

For now, you can stay as warm or as cool as you like, as long as you're not trying for maximum range.

5/26/2014: I've performed additional testing. Here are some results.

The behavior where the FFE’s HVAC system energizes the heater while in A/C mode is complex. Here are observations I have made which characterize the system’s apparently energizing the electric heater to balance cooling in order to maintain a target temperature. Notice that the results are dependent upon a combination of ambient temperature and selected HVAC target temperature:
  • First, configured the Message Center display (left of the speedometer) to display MyView, and configured MyView to display Accessory Power. With HVAC off, the Climate level displayed no power use.
    • With outdoor temperature reported as 98°F, in bright sunshine:
    • Turned on the HVAC system, and turned on the A/C (NOT using “Auto” mode).
    • Set target temperature to 73°F. 
    • MyView displayed about 1kW of power use for Climate.
    • After allowing the A/C to cool the cabin for 20 minutes of driving, only small variations in Climate power use occurred. 
      • This is apparently because when outside temperatures were very high and the vehicle was in direct sunlight, the A/C was unable to achieve the temperature.
      • Increasing the target temperature while observing the Climate power level, the power level increased to 5+kW when the target temperature was set to 78°F - apparently the current measured cabin temperature.
    • CONCLUSION: At very high outdoor temperatures, the system is incapable of cooling the cabin to what might be considered typical comfort temperatures: i.e., 72-75 degrees F. Because the system cannot achieve the selected temps, the heater is never energized to balance the refrigeration system. 
  • With outdoor temperature reported as 80°F, in bright sunshine:
    • Turned on the HVAC system, and turned on the A/C (NOT using “Auto” mode).
    • Increased the target temperature until MyView’s Climate power increased to over 5kW - in this instance, this occurred at 75°F.
    • Reduced the target temperature to 74°F at which point Climate power dropped to less than 1kW. (Setting the temperature to "LO" appears to constantly use 1 to 1.5kW, so setting a target temperature does potentially use less power, but only if the user constantly adjusts the temperature to chase the cabin temp.)
    • After allowing the A/C to cool the cabin for less than a minute, Climate power raised to 5+kW.
    • After a few minutes more of operation, Climate power fell again to under 1kW. Allowing the system to continue to run resulted in the repeated cycling of the 5+kW Climate reading.
    • CONCLUSION: At warm outdoor temperatures (which in conjunction with greenhousing effects create uncomfortably warm cabin conditions), the A/C system can easily cool the cabin to the desired temp. When that temperature is achieved, the HVAC system energizes the heater to balance the refrigerated air. 
  • With outdoor temperature reported as 62°F, at night:
    • Turned on the HVAC system, and turned on the A/C (NOT using “Auto” mode).
    • Increased the target temperature until MyView’s Climate power increased to over 5kW - in this instance, this occurred at 64°F.
    • Reduced the target temperature to 62°F at which point Climate power dropped to around 1kW.
    • After allowing the A/C to cool the cabin for 20 minutes, Climate power never increased.
    • CONCLUSION: Uncertain. The implication is that the A/C system was incapable of reducing the cabin temperature enough for the interior thermometer to register 62°F. It’s unlikely that any user would wish to cool their cabin in these conditions, however.

Sunday, May 11, 2014

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.

Friday, February 14, 2014

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.


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.
  • 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 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.


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.


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. 

Thursday, February 13, 2014

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.


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 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.


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.


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.


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." 


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.


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.

Tuesday, January 21, 2014

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.

Wednesday, January 15, 2014

Cabin Heat - the Enemy of EV Range?


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.


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.


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.