Take a look at the Raychem Polyswitches. The battery should be able to take
anything they will allow to pass before they trip and after the short is
removed they reset themselves. I have used them on power busses for medical
equipment. The only complaint is they cause a slight voltage drop that you
need to take into account.


At 09:53 PM 1/21/98 +1100, you wrote:
>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
>
>
Larry G. Nelson Sr.
mailto:L.Nelson@ieee.org
http://www.ultranet.com/~nr