Why is the gain in capacity of a D or C battery over a AA so little?

Question

I've been looking at AA's to power my next project, and the typical Energizer AA rechargeable offers between 2300mAh up to some that I've seen with 2450mAh. I thought that moving up to a C or D battery would increase the current availability significantly, however for the Energizer in the same product line, both the C and D batteries are only 2500mAh...

Why is the increase so little for such a significant change in size?

gkk_72 · Accepted Answer

Because they aren't using the full capacity of the battery size.  In other words, they have a smaller cell and place it into the C or D size battery form.  If you want a true D or C rechargeable battery you will need to go elsewhere for it.

Here is a link for a D cell battery that is 10000mAh

http://www.zbattery.com/NiMH-D-Cell-10000mAh-1-2V-Battery

Here is a 5000mAh C cell

http://www.zbattery.com/NiMH-C-Cell-5000mAh-1-2V-Battery

tom7railway · Answer

I am surprised that any AA, other than perhaps Lithium,  will claim 2450mAH, perhaps it's a misprint ?
Even a small 6 volt leadacid, which I would expect to way outperform 4 x AA cells, will only be 4AH.
I'd certainly use a small SLA (sealed lead-acid) if the voltage is right & project can spare the room.
SLAs are better for power applications because they have a really low internal resistance. 
But you do need to have a fuse because lead-acids can deliver a huge current if shorted out by accident or a fault, they will fry the wiring and maybe start a fire..

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Why is the gain in capacity of a D or C battery over a AA so little?

2 Answers