My First EV, Part V: My First Long Trip
Six months after buying my first EV (see My First EV — Part I), the time has come for the first long trip — Cupertino to Huntington Beach, about 420 miles each way. We decided to go on Highway 101 rather than 5, about 20 miles longer, but a prettier drive. We took two days to get to the destination, with one overnight stop in Santa Maria and one day to get back home.
We drove 931 miles, including a few trips to the beach. We charged on the road six times at fast charging stations, paying an average of $0.47/kWh. We charged overnight at the Hampton Inn in Santa Maria at a Level 2 slow station, and overnight at our host in Huntington Beach, which had a Level 2 charger in his garage and was kind enough to let us use it.
We spent 3½ hours charging on the road and about 16 hours driving. All of the fast charging stations were in shopping centers, welcome stops for bathroom breaks, coffee, or light shopping.
We bought 138 kWh of electricity, spending $64 for it. This could have bought us about 11 gallons of gas, leading to an equivalent 84.6 mpg — a little less if I factored in the free charging at our host.
Five out of six times, we charged at Electrify America. Four stations had 4 chargers each, and one had 11. Multiple charging slots were always available. With convenient credit card payment, I would give it five stars and always look for it on the road.
Once we charged at a ChargePoint station. There were also 4 chargers, but you have to use your smartphone, which I do not appreciate. Four stars.
In Ventura, we tried charging at PowerFlex. It had many charging stations, and after spending about half an hour there and on the phone, I gave up. Zero stars. I will never ever use PowerFlex again.
Before leaving home, I made a list of all of the fast charging stations on the route, but it was not necessary. The Bolt GPS has a convenient Charge Stations tab, which lists them by distance. Too bad you cannot sort out Level 2 chargers, which give you only about 25 miles/hour, compared to more than 100 miles/hour at a fast charger. Level 2 chargers on a long trip are useless.
Charging overnight at the hotel was a little bit of a surprise. It had four charging stations. I asked at the reception if I could leave the car plugged in overnight and they said “sure.” In the morning, I found out the charge was $28, or about $1.41/kWh. They charged for the idle time more than for electricity. … This was not disclosed on the charger or at the front desk. There was not an easy way to avoid it, though, since I did not want to wake up at 3:00 AM to unplug the car, but it would be easy to avoid with better planning.
I drove all the time with the cruise control set at 65 mph. The Bolt averaged 4.1 miles/kWh, or about $0.12/mile. The A/C was on for most of the trip — it had about 4% impact on the energy consumption.
Drive Slower To Get There Faster?
It seems contradictory, but in an EV, it might be true. Those readers mathematically inclined know that E=mV2. “E” is energy, “m” is the weight of the car (mass), “V” is the speed. There’s not much you can do about the weight. The empty Bolt weighs 3,700 lb, about 4,000 lb loaded. Saving 40 lb would add only 1% to your range, but try to leave the kitchen sink at home if you can.
Oh, but “V” is a killer, since it comes into play squared. To make it simpler, at 85 mph, your energy consumption is twice that at 60 mph. For a short trip, the faster you drive, the sooner you get there. But things are different if you have to charge.
On the return home, I drove 420 miles in one day. If the trip would have been on a flat road, with no traffic, at 60 mph I would have driven for 7 hours. At 85 mpg, I would drive only 5 hours — if I could keep the speed constant. I am not factoring in the time spent with the highway patrol, which could vary depending on the mood of the officer who stopped you.
At 60 mph, the Bolt goes about 4.2 miles/kWh. This is not only my empirical observation, but after my 900-mile trip on cruise control set at 65 mph, the dashboard displayed an average of 4.1 miles/kWh. To find the ideal speed, I need the reverse number, 1/4.2 = 0.24 kWh/mile. To find the energy spent per hour, I multiply 60 mph by 0.24 kWh/mile and I get 14.4 kWh/hour.
Assuming the electric motor’s efficiency is not influenced by speed, I use Einstein’s formula to find out how much energy is spent per hour at various speeds:
At 50 mph: (502 / 602 ) x 14.4 = 10 kWh/hour
At 85 mph: (852 / 602) x 14.4 = 28.9 kWh/hour
On a fast charger, the Bolt can take about 35 kWh per hour. All the fast chargers I used were not on the freeway, but in shopping centers nearby. It took a 5-minute detour to get to one, a few minutes to plug and pay, and another 5 to get back on the road. So, that’s about 15 minutes overhead on each charge.
If you charge from 20% up to 80%, each charge can give you about 40 kWh. I’ll assume 35 kWh since you might not be able to time it perfectly.
The results for a 420-mile trip are in the next table.
Last Hour Range Anxiety
Our last charge was in King City, at a ChargePoint station 110 miles from home. I charged for only 15 minutes, until the odometer showed 170 miles of range. Anxious to get home and with 60 miles to spare, I thought I could drive fast. I call “margin” the difference between the car’s listed range and the distance to the destination. Feeling safe with the 60-mile margin, I pushed it. Seventy mph, 80, 85 — I was just keeping up with the traffic.
The margin started to drop like a punctured balloon. Sixty went down to 50, then to 30. When it got down to 10, I realized I had to charge or slow down. My wife said “charge,” but I did not want another stop. “Let’s try slowing down,” I said. I dropped the speed to 60 and my margin started to creep up. I got home with 22 miles to spare and plugged it in. The next morning, I would have another 260 miles to go. Maybe 300 if I drove around town. I have solar, so charging at home is free.
Conclusions
Disclaimer: I am not advocating driving slow, except when it makes logical sense. Driving fast is often useful, and sometimes even pleasant. I once pushed my motorcycle to 100 mph briefly, just to see how it feels. It feels like flying low. But I am not advocating driving fast either. Do it at your own risk.
Several times in my life, I drove almost 1,000 miles in one day, obviously using an ICE. It was not a pleasant experience — exhausting and prone to tickets. I would not engage to more than 500 miles per day with the Bolt. Maybe a Tesla can charge faster and go farther. However, driving slow was a new and refreshing experience. The Super Cruise helped. After the 10-hour trip (with stops), I arrived home rather fresh and ready for dinner.
Is it worth it to drive 420 miles at 85 mph in order to save 15 minutes? Considering the extra cost, the wear and tear on the car and tires, and the possibility of Highway Patrol encounters, I think the answer is obviously no.
Is it worth it to drive at 50 mph and spend an extra hour on the road in order to save $10? I do not think so. Interestingly enough, the Bolt seems to be optimized around the speed limit.
By Mihai Beffa, CEO of SequentMicrosystems.com. Also see part II, III, and IV.
Featured photo: Electrify America gets * * * * *
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