Battery Capacity Measures

[JohnInStockie]

I was looking at the energy density of the A123 batteries, and was quite impressed until I actually calculated their energy density vs other NiMH types. So I am not sure if I have done it correctly.

The way I calculated this was :-

The Voltage x Amps to give me the energy capacity in Wh

divided by

Pi x height x Radius squared to give me the volume in cubic centimeters.

Doing this gave me:-

A123's h = .652cm, r = .26, vol = .138 cm3, v = 3.3, ah = 2.3, ED therefore = 54.8 WH/cm3
Yuasa's h = .57cm, r = .31, vol = .172 cm3, v = 1.2, ah = 9, ED therefore = 62.8 WH/cm3

Am I missing something?

John

 

[Ian]

John, it seems you used the diameter instead of radiius and your dimensions in cm are a tenth of what they should be (1cm=10mm), eg the height of the A123 should be 6.52cm or 65.2mm. That doesn't alter the fact that the NiMh has a superior energy density by volume, my calculations giving 0.69 & 0.78 Wh/cm3 for the A123 & Yuasa cells.

By weight the A123 fares better with 108 Wh/kg as oposed to 67 Wh/kg for the NiMh.

 

[JohnInStockie]

Thanks Ian. Does this mean that Nimh are best for energy density then? I am thinking if/when I recell, I would like to have it recelled with the greatest possible energy density.

 

[Ian]

It seems NiMh have the best energy density by volume but not by weight.

NiMh cells are by far the easiest to use from a diy perspective though, especially as you have the option of using a reasonably priced pre-assembled cell pack from powacycle for which a purpose made charger is available.

 

[flecc]

It's best to use the original Giant thermistor and charger with the Powacycle pack when recelling though, since the Powacycle charger is a fairly low quality one without a discharge function.

Recelling details on my site.
.