was it really humid when you measured the GF? are your aluminum
battery racks painted or otherwise isolated from the batteries (besides
the thermal grease)? how do things look when you are not charging?
Seth
On Friday, September 20, 2002, at 01:07 PM, David Brandt wrote:
> Boy, am I steamed. I put all that effort into getting good pack
> isolation,
> and the next thing I know, the car has aground fault, seemingly right
> in the
> middle of the pack. The really weird thing is that I have an odd
> number of
> batteries, and the fault really is *exactly* in the middle of the pack.
> Voltage from ground to the positive terminal of the most positive
> battery in
> the rear pack is +2.8V. Voltage to the negative terminal is -3.6V
> (this was
> while charging). How is that possible?
>
> For reference, I have 19 (10 in the back, 9 up front) brand new,
> spotless
> US-125's with only a few cycles on them. Up to this point, they had
> perfect
> isolation. I've checked the obvious things, and cannot find any
> reason for
> this. There is no corrosion, no acid misting or spills, no other
> wires that
> lead to ground in contact with the batteries or the posts, and all the
> connections are covered. The batteries sit on aluminum sheets which
> are on
> top of heater pads (not hooked up yet), which are on top of 1/8" thick
> fiberglass/nomex honeycomb panels. There is silicone heatsink grease
> between the batteries and the aluminum, and between the aluminum and
> the
> heater pads. there is silicone adhesive between the heater pads and
> the
> honeycomb, and between the honeycomb and the racks.
>
> If the batteries were dirty, I could see a fault between the rear rack
> and
> the center cell, conducting through acid mist. But as I said, these
> batteries are spotless, with no acid on the outsides.
>
> Any advice?
>
> David Brandt
>
>
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