I'd visit the local drugstore and look over the rack of digital camera and
watch batteries.  Whatever you find there will probably be readily available
at least for a couple of years.

We've been using DL123 2/3A lithium batteries, and they pack an impressive
wallop.  One of our applications is sucking over 800 mA from these little
things (a few mS at a time), and getting nearly full rated capacity out of
them.

When buying them in quantity, we found that we could not get them packaged
without the retail shelf cards because without them they exceeded some ICC
rule about energy density.  If you could short out a whole box of these
critters, you could generate a LOT of heat.  Supposedly they have some sort
of fusible link inside that will keep them from actually exploding if
shorted out, but with the right load, you can get several amps for quite a
while.

A coin cell based on the same chemistry should be able to supply your
current without sending you to some exotic source to get them.

The 3V cells start out something like 3.6V, but within seconds of load being
applied drop to 3V and stay there for a long time before they start to drop.
To suck them dry, you need to hang in there until they drop so something on
the order of 2.2V, at which point you've gotten 90% of the capacity.  You
need either voltage-tolerant circuitry or a switching regulator to drain
them efficiently.  Some of the L-series PIC's are a very good match for
these cells.

> -----Original Message-----
> From: Sean H. Breheny [mailto:shb7@CORNELL.EDU]
> Sent: Saturday, November 18, 2000 8:01 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]: Small batteries
>
>
> Hi all,
>
> Two quick battery questions:
>
> What type of battery would you recommend for a situation
> where you need
> about 9V, 20mA, for about one minute at a time (followed by about 30
> minutes of off time), repeated several times? The battery
> must be as small
> and light as possible (this is for a model rocket altimeter).
> Are there
> coin cells capable of this current level? If so, several
> could be stacked
> to get 9V.
>
> Secondly, I remember small (smaller than AA size) 12V batteries being
> discussed here some time ago, but I can't find a supplier or
> the name of
> the type of battery. I think they might be used in wireless
> controls (such
> as car door lock transmitters).
>
> Thanks,
>
> Sean
>
> --
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>

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