Ronald J. Parigoris wrote:
> The new fangled Nickel Metal Hydride cells are pretty amazing. If
> I made up a Zapped 12 cell pack of lets say 2600mAs, unloaded
> voltage would be 14.4 volts.
For emergency backup such for the 914 pump, rechargeables have a
self-discharge problem making them undesirable as a standalone source.
Though one could constantly trickle charge them with the main system at
a rate which doesn't warm them up. OTOH, shelf life of alkalines is
several years and they are dated, but you're right in that you'll get
better high-discharge rate performance from NiMH's.
The 2600 mAh spec is not comparable to that for storage batteries. A
spec sheet may say 18,000 mAh for an alkaline D-cell, but that's at a
minuscule discharge rate down to .8V. The graph in Energizer's "Pink
Bunny" spec sheet stops at 1 amp discharge rate (the pump is 3A for
planning purposes), and the curve of the line suggests we're looking at
minutes here! It would certainly take a pack of 2 x 8 or 2 x 9 D-Cells,
and then only after test like Dave did.
I note that Dave didn't get 2 hours of 3A pumping on a 7 Ah battery,
terminating at 10+ volts per that usual spec, because it may be based on
a 20-hour discharge rate.
Best,
Fred F.
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