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.
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.
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 hoursIf 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.