[ausev] A/C in an EV

[Gil Dawson]

I don't have power consumption figures, but GM's EV1 and S-10E, and 
Toyota's Rav4-EV, all use an electric motor integral with the 
compressor.  GM's version uses a synchronous motor driven by a 
variable-frequency 3-phase 120V power conversion module running off 
the traction batteries.  The frequency is varied to continuously 
adjust the amount of cooling to the demand, rather than turning on 
and off.  The A/C is used to cool the NiMH batteries, too, so it will 
come on automatically while charging, or even while sitting in a hot 
parking lot.  There are two evaporator coils: one for the cab and one 
for the battery compartment, each activated separately somehow.

The effect on range is barely noticable.  Sitting in a cool cab in a 
parking lot on a warm day with the windows up, I can watch the 
State-of-Charge meter drop very slowly.  Sometimes in the summer when 
I'm going into the store for just a few minutes, I leave the A/C on 
so the cab will be cool when I return.  Can't do that with an ICE.

This design works fine when it's working, but it is probably much 
more complex than necessary.   The power conversion module is very 
expensive, about $4K, and they are not making any more.  Without it, 
charging will stop when the temperature of the batteries gets above 
80-something degrees F, so, when the power conversion module broke 
last summer, my truck was inoperable until I found a new one. 
Fortunately, with some help from my friends, I did.

--Gil