Digression...
Quote:
Originally Posted by MD2000
...Another problem with parallel cells is that a short in one cell will suck heavy currents from the other 2 cells, making the pack a dangerous device.
You never see NIMH cells used in parallel for that reason...
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Actually, multiple-AA - to - D cell "converters" (plastic containers) are widely sold. Most take two AA cells, but some take three. The going price in eBay is $0.99, including shipping. Search eBay for:
2 AA to D
Parallel-connected 3xAA-to-D converters are less common,
but do exist.
There are even some 4xAA-to-D converters out there, but the result is a slightly-oversized D cell:
diameter of 1 AA battery = 14.5 mm
diameter of 4 AAs = (1 + sqrt(2)) x (diameter of 1 AA) = 2.4142 x 14.5 mm = 35.006 mm
which is 0.806 mm oversize
compared to the diameter of a standard D cell, which is 34.2 mm
My guess is that if a short developed in one AA cell, it would do so gradually enough that it wouldn't be dangerous, because the stored charge in the other cells would not discharge through the short all at once. (Be careful when loading the batteries into the converter, though, that you don't put in batteries with different initial charge levels!)
Of course, unfortunately, without 10C or better AA cells, none of these could be used in HEV battery packs.