[ausev] Converting a vehicle

[Gil Dawson]

At 3:01 P -0600 2/19/08, Chris Robison wrote:
>NiMH batteries are a difficult issue in EV packs due to their exothermic
>behavior during charge and high-current discharge. On smaller packs for
>bikes and some small scooters it's not such a big deal, but for larger
>vehicles that have NiMH packs, the Ranger and I believe the EV1 used
>redirected air conditioning output to keep them cool.

This is indeed a big deal on the GM S-10E production electric pickup 
truck.  The NiMH batteries are in a sealed compartment under the 
truck bed (taking up no cargo space).  To keep them cool while 
charging, an evaporator coil and fan separate from the coil and fan 
in the cab are used.  The condenser coil and fan behind the 
"radiator" grille are used for both air conditioning and cooling the 
batteries.  From what I can tell, the batteries don't seem to be 
actively cooled while driving, only while charging.

I have an anecdote to illustrate the degree of NiMH exothermic 
behavior during charge.

When the condenser fan motor went out a few months ago, the truck 
would not charge, at least not in the summertime.  It would start, 
then stop with a "Check Vehicle" error after a few minutes.

After waiting a couple of days for the batteries to cool, I connected 
a Tech II to watch the temperatures.  Within seconds of starting the 
charger, the temperatures began rising and reached the computer's 
cutoff threshold (I forget the number) in four or five minutes. 
Blowing a 1/2 hp shop fan into the grille solved that problem and got 
us charged until I could buy (from GM) and install a new condenser 
fan motor.

--Gil