1.8AH 1C=1.8A, 10AH 1C=10A?

[jerry i h]

OK, I want someone to explain this to me (a little knowledge must be a dangerous thing).
2 NiMH batts, one a 1.8AH AA, and a 10AH D.
AA @ 1C = 1.8 amps,
D @ 1C = 10 amps.
Am I missing something?
If I am doing an ROP that pulls 5amps, then, it makes much more sense to use the D rather than the AA, since the AA will be putting out 3C, whereas the D will only be putting out 0.5C?
If we set aside things like MattK's hi-drain AA and Eneloops, all being equal, when I start doing ROP's, the D is better than AA?
I always thought the advantage was runtime, not current-out.

 

[Mr Happy]

It would sort of make sense that bigger batteries can supply more current, wouldn't it?

Even so, you need to look at the specific rating of each individual battery to see what it is capable of.

There is size to consider too. If you build a ROP with six D cells you will need a 6D host.

 

[TorchBoy]

AA @ 1C = 1.8 amps,
D @ 1C = 10 amps.
Am I missing something?

No, it really is that easy.

it makes much more sense to use the D rather than the AA, since the AA will be putting out 3C, whereas the D will only be putting out 0.5C?

You got it. :thumbsup:

If we set aside things like MattK's hi-drain AA and Eneloops, all being equal, when I start doing ROP's, the D is better than AA?
I always thought the advantage was runtime, not current-out.

Yes, D would be better, unless you're after something like a microROP. :tinfoil: The D cells can more easily cope with higher currents in the same way a man can not only work for longer than a boy (distraction issues aside) but he can do harder work too.

 

[TorchBoy]

Gotta type fast around here. As Mr Happy indicates, ability to cope with the load is not the only consideration. If the work the man and boy are doing is chimney sweeping, there are definitely advantages to being small. (Or disadvantages, as the case may be in that case.)

 

[jerry i h]

...If you build a ROP with six D cells you will need a 6D host.

Darn. The cat's out of the bag. I commissioned Wayne for the prototype 'Wall of Fire' (no, I had nothing to do with the name). While I do have an ROP in the works, my immediate concern was how to power this beastie. IIRC, he said that it pulls 6 amps (or was it 7?) and way more than a 3854HI, and I am skeptical that anything outside of a lab power supply can provide the amps. For the nonce, I ordered the 'massive' 6D version, which I will try to power with NiCds pushed to exhaustion. When I receive the batts and WOF, I will bump this thread...

 

[mdocod]

most NIMH D size cells can deliver 20 amps or better without a problem.

 

[jerry i h]

most NIMH D size cells can deliver 20 amps or better without a problem.

Noted. Assuming that cheapie NiCd's do not kill my WOF, I will buy MattK's NiMH's, and do a comparison.

 

[jerry i h]

I do not have my WOF yet, but have already changed my mind. I am concerned that the cell directly under the heatsink will be exposed to high temps. The usual spec is 140F; I do not know if this is just convention, or if really bad things happen above 140.
*attery*tation has some D NiCds of interest to me.
They list one by Sanyo that is high temperature.
There is also one by SAFT. I was able to Google the spec sheet, and it lists a 30 amp steady draw, and a 130 amp flash draw capability.
At this point, I have pretty much ruled out NiMH D's for my WOF, unless something really bad happens to the NiCd's.