On Sat, 18 Nov 2000 21:01:15 -0500, you wrote:

>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
Check out 1.5v alkaline button cells - they can be found way cheaper
than lithiums (<15 cents), even taking into account you need twice as
many for the voltage. 20mA would be no problem. The 12V batteries are
just a stack of alkaline button cells in a case - used for lighters
and car alarm keyfobs.

Do you really need a voltage as high as 9v ? Reducing this will
significantly reduce battery size. Maybe you only need 9v for a small
part of the circuit, for which you could maybe use a charge pump or
dc-dc converter, running everything else at 3v.

=46or minimum size & weight, you should look at using a DC-DC step-up
converter from 1.5 or 3V from alkaline buttons or lithium camera
batteries (e.g. CR2).=20

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