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I just discharged two Alkaline batteries, one from Ikea (20p each) and the other a Duracell M3 (85p). The load was a resistor that was the equivalent of the bulb in my 4 cell headtorch.

As expected the Duracell did last longer (564 minutes)  than the Ikea el-cheapo (410minutes)

But when you factor in the cost, the Duracells cost THREE times as much to use as the ones from Ikea.

Makes you wonder why anyone bothers to buy the Duracells, I supose some mugs have to pay for the cute bunny adverts.

I will check an Energizer (the offer from Asda) and see how well they do.

Quote: Originally posted by halfpiste on 28/01/2005

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Stuart, you've got WAY too much time on your hands! I'd be interested in seeing how a high end (2300mAh) Nimh battery does though.

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Fairly easy to calculate capacity, if you know the load and the start and end voltages.

There no real need to measure the NiMh, they will deliver the rated capacity (i.e. 2300mahr) more or less independant of the load. Its alkalines that cause the problem, at high rates of discharge the mahr capacity will be lower than at low rates of discharge, if that makes sense.

In the test I did I would estimate the capacity of a Duracell M3 to be 1900mahr at the rate of discharge typical in a low power torch.  

I have a battery analyzer which will automatically discharge and measure the capacity of batteries, but it really needs a stack of 4 batteries to give an accurate result,  and in the case of Duracell Alkalines thats expensive.

The Enegizer lasted 494 minutes, so with 4 batteries required to run my headtorch it would cost per hour to run;

On Ikea batteries  12p

On Energizer batteries (special offer) 15p

On Energizer batteries (normal price) 30p

On Duracell batteries 36p