[ausev] Sick Prius

[Gil Dawson]

I don't know whether it applies to Prii, but replacing a single  
module in my Chevy S-10E's NiMH pack was a big magillah.  The problem  
we had was the computer shuts the truck down if the voltages on all  
26 modules aren't within a tiny tolerance.

What we did was:

1) We woke up the new module by deep cycling it several times.  We  
rigged up a nest of light bulbs and nichrome wires that would  
discharge the cell overnight.  A tripout relay would open when the  
discharge was deep enough, and we could adjust the discharge current  
by adding more light bulbs.  Then we would charge that module on a  
commercial battery charger the next night. We went through several  
cycles over a week.

2) Using a 400VAC variable transformer and a diode, we charged the  
remainder of the pack in series until all the modules -- including  
the new one -- were within 0.2 volt of each other.

3) Then we slipped in the new cell, closed the lid, and handed the  
pack back over to GM's Battery Pack Control Module software.

The first trip was disappointing, because the battery voltages got  
out of tolerance after about 25 miles, but the truck's calculated  
range has been slowly climbing since last August.  The new module  
still gets out of tolerance first, but it lasts nearly 35 miles now.

--Gil