# Maximum current draw for D alkaline's



## Mr.Penny (May 20, 2010)

Just curious, I know the maximum current draw for AA alkalines is 900mAh. So when using D cell alkaline's, does that mean that the current draw can be increased to a higher number? And if so, how high?


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## 45/70 (May 20, 2010)

Mr.Penny said:


> Just curious, I know the maximum current draw for AA alkalines is 900mAh. So when using D cell alkaline's, does that mean that the current draw can be increased to a higher number? And if so, how high?



I think you're probably right, but for example Energizer's .pdf's on their site seem to indicate 1A as a normal maximum discharge rate. I think the original idea behind the "D" size cell, was more along the lines of increasing the available capacity, rather than providing more current.

Dave


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## Mr.Penny (May 20, 2010)

Thanks, that's exactly what I needed to know...


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## Mr Happy (May 20, 2010)

Mr.Penny said:


> Just curious, I know the maximum current draw for AA alkalines is 900mAh. So when using D cell alkaline's, does that mean that the current draw can be increased to a higher number? And if so, how high?


You are a bit mistaken about the question you are asking.

There is no maximum current draw for an alkaline cell. The maximum capacity will be achieved if the current draw is zero. As you draw more current the capacity decreases. Even 100 mA will give less capacity than 1 mA, and by some reckonings 500 mA from an AA cell is too much.

The same goes for a D cell. A D cell can manage 1 A, but it will have a much higher capacity at 0.1 A, and higher still at 0.01 A.

You have to make a cost/benefit choice about what amount of current you can afford to draw and how often you want to replace the batteries.


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## Mr.Penny (May 21, 2010)

Oh! I see what you mean...

How about this scenario, let say for example that cost is not an issue, at least two hours of runtime and a minimum voltage of 1.10 is needed.

I checked the Energizer's datasheet on E95 D alkaline's, the graph doesn't show beyond one amp, but I'm guessing if it continued draining to 1V, I would end up at about 1.1A draw, so with 1.10V I should end up with 1A maximum draw (with the requirements above). Does this seem correct?


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## Lynx_Arc (May 21, 2010)

you could probably do 1.5 amps out of a D cell but not for an extended period of time. If you need to go beyond 1 amp it is time to use nimh or nicad or redesign for lithium chemistry of some sort.


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## tocs (Jan 2, 2013)

I don't know if people will see this since the thread is so old but I thought I should try an existing thread first. What perplexes me is not that the capacity of an alkaline D cell decreases with current, but that it doesn't seem to be any more robust against capacity loss with increasing current than a AA. Looking at the Energizer data sheets, the capacity of either the D or AA at 500 mA is about half what it is at 25 mA. (I read D: 20 Ah / 10 Ah and AA: 2.8 Ah / 1.4 Ah for 25 mA / 500 mA current from the data sheets for the E95 and E91 respectively.) Maybe this is peculiar to Energizer, consumer alkaline, or maybe it is the cell layout, that is what I would like to know. I could do much better by using say 7 AA cells in parallel which would be 19.6 Ah at very low current (25/7 mA) but then for 500 mA TOTAL current each would be at about the 70 mA capacity, which looks to be about 2.5 Ah. So my total capacity at 500 mA current would be about 17.5 Ah, not 10 Ah as with the D cell. I guess I have been thinking that D cells could take more current draw than AA without capacity loss, act more like parallel AAs, but obviously I am wrong!

I am not talking about cost mind you, I know 7 AAs cost more than 1 D. It's just the logic (or my lack thereof please point out!!). Guess maybe it is just that Ds give more capacity, and paralleling smaller cells is the way to get more current without sacrificing capacity. By the way, the D is about 148g mass and the AA is 23g, a ratio of about 6.4 consistent with the choice of 7 to parallel AAs to match capacity at very low current < 25 mA given that the D gains a bit of advantage not having the extra case weight of the 7 AAs.

I just opened an old 6D flashlight that a friend had for a year and there was a leaking D alkaline. I had turned it on at her house a few days ago and it worked... but not now. I also just found a leaking Duracell Ultra AA on my table that was fine when I tested it yesterday. If this is not a *sign* when writing a post about Alkaline cells, I don't know what is.


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