FYI the smallest battery that packs enough energy to turn motors etc that
is available commercially is the CR2 lithium (photo supply). This has
impressive characteristics and is surprisingly light. It is also expensive
when not bought in bulk. FYI camera winder motors often draw 1.2A for a
few seconds at a time from such batteries. The voltage is well in range
for a pic (perhaps with a LDO regulator or a silicon series diode or two
to go to <5.5V. The short circuit current can be very high. I think that
the batteries have built in overcurrent protection.

Anyway Lithium has the highest Wh/kg density. A Li-ion battery can be used
for rechargeable duty for 'lightweight' projecs. 7.2V nom 0.8Ah weighs
under 75 grams.

Peter

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