[BrianG]

Yeah, another battery-related discussion... I know Li-Polys would be better than NiMH in everything but price, but for those still using NiMH cells;

Maybe this has been discussed before (search turned up nothing relevant), but I have a bunch of NiMH AA 2300mAh batteries laying around and was wondering about the advantages and disadvantages of using these instead of the normal sub-C cell packs.

For a little background, I did a little measuring and calculating:

AA's (Duracell)
- 2300mAh
- Cell Diameter = 14mm
- Cell Height = 49mm
- Cell Volume = 7542.9 mm^3
- Cell Weight = ??
- A pack of 14 AA cells, wired in series, in 2x7 arrangement takes up 134456 mm^3 of space.

Sub-C's (GP3300 cells)
- 3300mAh
- Cell Diameter = 22mm
- Cell Height = 42mm
- Cell Volume = 15965.6 mm^3
- Cell Weight = ??
- A pack of 7 sub-C cells, wired in series, in 1x7 arrangement takes up 121968 mm^3 of space.

AA Advantages of using 2 AA cells in parallel vs 1 sub-C cell
- 39% increase in battery capacity/runtime, providing manufacturer ratings are not exaggerated.
- 48% increase in surface area to aid in cooling.

AA Disadvantages of using 2 AA cells in parallel vs 1 sub-C cell
- 5.8% decrease in battery cell volume (actual voltage/current generating volume)
- 10.2% increase in battery dimensions (tray real-estate) needed.

I figure two packs of 7 GP cells could theoretically be replaced by two packs of 14 AA cells. Each of the 14 AA cells in one pack would be wired in series for a full 14.4v. Then, both packs could be wired in parallel. Despite the two disadvantages I could think of, would the increased capacity offered by the AA cells be useful? Also, what is the discharge rate of AA cells? Weight could also be a consideration.

Price is also a factor. Two Sanyo 2500mAh cells cost about $6.50 (quoted from BallisticBatteries.com), while a single GP3300 cell runs for $5 from rc-monster.com. That's a 30% increase in price.

Ideas/thoughts?