Re: Cold NiCd/NiMh batteries

"Ted Edwards" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> I have a 12V 60Ah, vented cell NiCd battery.  I tested this at
> -40degrees with a 500A load and got 5min to a 9V end point.  A
> theoretically perfect 60Ah battery would have given 600A for 6min so
> this is truly impressive performance.

Indeed!

> My question: I hear from many sources that modern NiCd and NiMH cells
> have very poor cold weather performance in GPS receivers and digital
> cameras.  Does any one know what the difference in chemistry and/or
> construction is that leads to the poor performance?

The cylindrical spiral wound consumer cells don't fare nearly so well, but I
wonder if the cell self heating was significant in this case.  A slower
discharge might have done much worse.