Sean:

The 12 volt battery you are referring to is Eveready # A23 and has about
a 30ma/hour rating. It does seem to supply the current that you need
from my own experiences. If you only really need 5 volts, consider a 6
volt battery and a series diode.

Many alkaline and lithium batteries exist in small sizes such as
Eveready A544 (alkaline) and L544 (lithium). Duracell makes a 7.5 volt
alkaline battery in a slightly longer case under the # MN175B. The 6
volt and 7.5 volt batteries are typically LR44 (alkaline) or SR44
(silver oxide) stacks. It is interesting to note that the lithium
batteries are specified as having about twice the amp/hour rating of the
alkaline batteries and cost about twice as much. Coincidence?

You might be able to stack several of the SR44's in a length of tubing
installed into a N-cell holder.

-- Rich


"Sean H. Breheny" 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
>
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