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Test spin in a plugin Prius
5/25/06

Last Tuesday I got the chance to briefly drive the California Cars Initiative’s Prius plug-in hybrid, converted by EnergyCS/EDrive. Unfortunately, I only had about three minutes behind the wheel, and about another three minutes riding in the back, but I did get a basic feel for it.

Overall, it drove more or less like a normal Prius. I felt that it was a bit slower off the line when I really stepped on the gas, though CalCars founder Felix Kramer assured me this was only because we were lugging the weight of four people. The car seemed much happier to stay in electric-only mode compared to the Prii I’ve driven in the past. In the past, I’ve been driving in hotter weather with the AC running, which may help explain this difference, though the larger battery probably helps. In this case, it seemed that the gasoline engine might not have come on at all if I hadn’t stepped on the gas pretty hard a couple of times. On our admittedly short trip around downtown DC we averaged over 100 miles per gallon of gasoline, although this does not account for the energy or emissions associated with charging the battery.

The car uses a lithium-ion battery pack stored underneath the rear floor. In the stock Prius, there is a storage area in this space, but it seems to hold the battery nicely. The biggest problem with the battery pack is that it makes it impossible to get to the spare tire, but Kramer told me that the next generation of conversions from EnergyCS/EDrive would have a more compact battery pack that would allow access to the spare. There is no word yet on battery life, but they are aware that it may be shorter than in the stock Prius, due to their charging and discharging the battery more severely. The electricity supply for the car comes from a standard 120V outlet, meaning it can be plugged in just about anywhere.

The plug-in Prius uses a custom battery management computer with the stock engine management computer. It also has a nifty gauge installed on the dash that shows how close you are to engaging the gasoline engine (unlike the stock Prius, which tells you whether the engine is on, but does not give you any way of knowing when it is about to engage). This feature will help the truly dedicated driver to keep his car in electric-only mode as much as possible.

In sum, the conversion seems to be done pretty well, requiring only the sacrifice of a little bit of storage space. We’ll have to wait and see what reliability is like, especially with respect to the battery pack. And finally, although it delivered good MPG numbers with respect to gasoline, we do not know what the efficiency is like with respect to the charging and discharging of the battery. Hopefully, CalCars will publicize charge histories for their vehicles, so we can evaluate not only the gallons of gas, but also the number of kilowatt-hours that have gone into them.

Posted by: Don 5/25/06

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