William "Chops" Westfield wrote :

> A type 394 watch battery 
(PROBABLY 
> available in alkaline (general purpose), silver (camera),
> and zinc air (hearing aid) with slightly different part numbers)
> is 
3.6mm tall (so you couldn't fit 10 of them in the space of a
> A23, but 
4 and a spacer would be no problem) and has
> about twice the mAh 
capacity.

Hi.
Just thinking out loud here...

Other posts have also 
been talking about getting a lower
voltage battery with a higher mAh 
value (in this case "twice"
the capacity).

Now, Let's say we have a 
12V/100mAh battery and one
4.5/200mAh battery. Now, the 4.5V battery 
*seems* to have
double capacity (which most equals with "lifetime" 
under
similar conditions). But, if using a well designed step-down
converter, will that not draw *less* current from the higher
voltage 
source, then the target is using ? Or in other words,
if one could 
expect a 100% efficient converter, is it not realy
the V x mAh value 
that is interesting, not ? Even if the
converter runs at something like 
80-85%, I think that
one can not just compare the mAh values 
directly...

I'm not claiming to be an expert in this, just liked to 
know...

Jan-Erik.



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