Hi,

May I draw on the eternal wisdom of the list?  I have a problem with
battery protection.

Our product uses a 12V 3AHr NiMh battery pack (and 3 PIC's).  The
battery pack is designed for use in rough environments, and for this and
other reasons, the terminals have been left relatively well exposed.
This is a problem if the battery is short circuited.  The batteries are
a small but expensive part of the unit.

Can anyone suggest a way of short circuit proofing the batteries?  The
method has to :

1. Be user-resettable after a short circuit, or self-resetting.

2. Respond very quickly after the current limit is exceeded (batteries
are quickly damaged).  Ideally the current limit will hardly be exceeded
at all, even for an instant.

3. Draw very little or preferably no quiescent current (NiMH
self-discharge automatically :-).

Some "resettable" fuses that we've tried are way too slow.  The current
limit by the way is 9A.

Any ideas?


Thanks.
David Lions
bjlions@magna.com.au.NOSPAM