4 hours ago
22 May 2011
100 mile range at moderate speeds as advertised by Th!nk, 96% charging efficiency
We drove one hundred miles on a single charge yesterday in our new Th!nk City EV. The low battery light came on at about 99.5 miles, and the gauge indicated several miles of range left, perhaps just under 10.
Most of this drive was done on back roads at speeds of 45 mph, but with many stops going through small towns. We used the air conditioning for about 25 miles, I guess. The usual EV driving technique of trying to slow down only with regenerative braking is instinctive for me after 25,000 miles driving the Mini E. However, it takes a bit more care in the Th!nk since the regen is not as strong as the Mini E regen. This technique is essential to getting the best range in an EV of course. And it makes a noticeable difference in gas cars as well, it is just not as noticeable since efficiency of gas cars is so very low to start with.
I plan to test the range again on the freeway in the Economy mode, which is 60 mph top speed, and hopefully later in the Drive mode, which has 70 mph as the top speed.
On this trip I took a Garmin GPS which indicated that my Th!nk City EV reads a little high on the speedometer, just like my wife's Honda. At 59 mph on the speedometer, the GPS says 55. While my wife's Honda has the exact same speed offset, my old Mercedes 240D read even higher, almost 7 mph off at 65 mph. However my Saturn agrees precisely with the Garmin.
Recharging the Th!nk after my 100 mile trip consumed 23.6 kwh, a bit less than the 24 kwh specified to charge fully from zero. Perhaps this is because I stopped when the low battery light came on, and I had several miles of range left. This agrees with Th!nk's claim of 96% charging efficiency. See slide #12 at this link, original source is here if you can open a PDF file.
Charge time agrees closely with the Frequently Asked Questions on the Th!nk website. They claim 18 hours for a full charge from 110 volts. I measured 19 hours 19 minutes.
The bottom line is that the Th!nk adds about 5.2 miles of range per hour when charging at 116 volts, versus about 3 miles of range per hour of charging at 110 volts for the Mini E.
This high charging efficiency is a significant advantage over the Mini E which in my experience took over 30 hours to fully charge from 120 volts, even though they claimed 24 hours. (At work, I could only charge the Mini E at 110 volts, there was no 208 volt supply available to me until near the end of the lease.) The Mini E battery pack is only about 16% larger than the Th!nk battery, so most of this difference is in charging efficiency. I do not believe this is AC Propulsion's fault, I suspect it has more to do with poor BMW decisions like running the battery cooling fans during charging even if they are not needed. (Keep in mind the Mini E is a prototype.) As I found out, this can be a fatal flaw when charging the Mini E outside in the winter unless you put a cabin heater in the Mini E. The Th!nk should have no such problem. In addition, the battery temperature range of the Ener Del battery pack is wider, on both the hot and cold extremes.
To be fair, the Mini E charging efficiency appeared to be much better at 220 volts, presumably because the parasitic fan power is a smaller percentage of the total.
The older fourth generation Th!nk reported had a charging efficiency of about 64%, consuming 18 kwh to fully charge the 11.5 kwh NiCad battery. Nice that our generation 5 Th!nk has more than twice the battery capacity and roughly 50% more efficient charging. But I do miss the 12 kw charge rate available in the Mini E, even if I did not use it much. The 3.8 kw charger in the Th!nk is a limitation for long trips.