Just thought I'd share some important info on buying rechargeable batteries...
When it comes to rechargeable batteries, bigger does not always mean longer lasting power.
Not well known is that even though they are physically MUCH larger, some rechargeable NiCd and NiMH "D" and "C" batteries (cells) have significantly LOWER mAh capacity than some rechargeable "AA" cells (e.g. a 1100mAh "D" cell v. a 2500mAh "AA" cell).
In some cases it may be much more cost-effective to use a AA cell and an AA-cell to D-cell or C-cell adapter casing instead of buying rechargeable "D" or "C" cells. It depends a lot on the retailer and the battery brand.
Worse, is that the lower capacity NiCd and NiMH "D" and "C" cells may cost 2X to 4X the price of a higher capacity AA cell of the same chemistry. For example, I found a quality 2500mAh AA NiMH cell for about $2ea in 4-packs when on sale, yet a lower capacity "D" or "C" NiMH cell at the same retailer cost almost $7ea in 2-packs.
I found that some of the NiMH "D" cells (including the larger case) weighed about the same as a quality 2500 mAh NiMH AA cell (lower weight is consistent with a lower milli-Amp-hours capacity battery).
I took apart a couple "no-name" rechargeable "D" cells and found a cheap, low-capacity AA-sized cell inside with just an air-gap in the case. The 'AA' cell was internally supported in the larger 'D' casing only by it's connections...which would make it less impact resistant. Some of the cells were rated at just 1100 to 1250 mAh! A well-known store-brand had a similar design battery. Clearly this is a way to make more profit by disguising an inferior product in a way the average consumer won't recognize...and it's perfectly legal as long as they don't make misleading claims. This is kind of like the industry trick of "shrinking" (providing less product in the same size package for same prior cost. You'll be seeing this increasingly often in grocery stores over the next few years. e.g. you'll get 11oz of cola instead of 12oz...or 14oz of chips in the same bag as the old 16oz size but for the same or higher cost as the old larger size/weight).
Worse yet, is you may be relying on the logical assumption that a rechargeable "D" cell will last longer than a "C" or "AA" cell, but your flashlight could "die" at the worst possible time.
However, much higher capacity 10,000mAh NiMH "D" cells CAN be found for much less $/mAh (e.g. $8ea on sale, $18regular price) and can be a good deal.
The point is that you first have to be aware of these differences and read the specifications on the battery and the package...if the mAh is even specified...sometimes it isn't or it's in incredibly tiny print.