AA's vs Sub-C's ?

[BrianG]

Thanks for the info people. I wasn't really looking for weight savings really - I just had a bunch of NiMH AA's laying around and was looking at the Ah capacities and got to wondering. Since I haven't been able to find the max draw rate of AA's, I thought I'd ask the knowledgeable people here. :)

I suppose I could take some of those AA's, hook up a resistive load, and seeing how the voltage drops at 5A, 10A, and so on. Maybe even use a few transistors and make a variable load circuit. However, this wouldn't be totally accurate as a motor is a mix of mostly inductive, a little capacitive, and some resistive for a sometimes complex impedance - and the signal feeding a motor is really square wave AC. Since I was planning to run two AA's in parallel to approximate a sub-C, I can just double the values. Since sub-C cells can be subjected to load currents upwards of 70-90A (or more), I'll have to load the AA's with 35-45A. To be fair, I should perform this test with a sub-C as well and note the difference in drop of voltage. Unfortunately, I don't have any more loose sub-C cells. :(

Another reason why I was toying with this idea is I was reading a thread in a different forum (sacreligious, I know) about using D cells and people said they have more capacity, but do not release heat as well due to their bulk. I also know that sometimes using a bank of small capacitors in parallel is better than one large one of the same total value due to the transient response to loads. I thought maybe these two factors may apply equally here.