eVolvo - Electron Hog
Posted by Max Dunn Mon, 23 Jun 2008 18:30:00 GMT
You have heard of a “gas hog”? Well my eVolvo is an electron hog!
Most electric cars get between 2 and 4 miles per kWh. The ones that are light and streamlined and have efficient AC motors with regenerative breaking get the best mileage – and my car is none of these. It is a heavy car with a big DC motor and no regenerative braking. It does have a lot of zip, but at the cost of poor electron mileage.
Battery to wheel, I get about 2.5 miles per kWh. This is based on my maximum range so far of 25 miles, the battery pack of 15 kWh maximum, and a Peukert effect that reduces the useable energy from the lead-acid AGM batteries to about 10 kWh.
However, the Soneil 1206S chargers that are being used are not very efficient, probably around 75%. That combined with charging efficiency of the batteries which is probably around 85% gives a charging efficiency of only about 64%. So from the wall to the wheels I am getting about 1.6 miles per kWh. This figure is consistent with the data I have been collecting:
| Miles | kWh | Charge Time | Miles/kWh |
|---|---|---|---|
| 22.2 | 14 | – | 1.6 |
| 6.6 | 4.3 | – | 1.5 |
| 4.6 | 3.4 | 6 hrs | 1.4 |
| 13.3 | 8.4 | 17 hrs | 1.6 |
| 18.3 | 11.9 | – | 1.5 |
Yesterday, I really pushed the eVolvo accelerating hard and going as fast as I could on the freeway for a few miles. I ended driving 9.8 miles and then when I recharged, it took 6.6 kWh of electricity. So I still got 1.5 miles per kWh which is the same as when I drove it conservatively. I was expecting to get less, so I am not sure what this means.
Also, when I was accelerating hard, it was pulling 300 amps and sometimes up to 400 amps. But on the freeway, it would only pull 200 amps, which made it difficult to accelerate past 60 MPH. My guess is that the controller normally limits the current to 200 amps because that is what the motor is rated at for continuous use, and only allows higher current levels for short bursts.
The other day, I measured 1.9 miles per kWh, which I thought must have been wrong since it is quite a bit higher than the 1.6 I have been getting.
But then again today, the eVolvo was completely recharged after going 27.9 miles (which was not one-shot but achieved with partial recharges between trips) and it took 13.8 kWh of electricity for over 2 miles per kWh! With charging inefficiencies, this probably means the eVolvo is getting 3 miles per kWh from battery to wheel and that I might get up to a 30 mile range.
I have been driving conservatively trying not to pull over 100 amps, so maybe this is why I am getting better mileage. I will keep my eye on this to see if it stays this high.