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Old 12-08-2010, 08:11   #1
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Calculate Amp Hours From Reserve Capacity ?

Searching, I found two references on how to calculate average amp-hours using reserve capacity.

Amp/Hours = 0.6 * reserve capacity

Amp/Hours = (Reserve Capacity / 2) plus 16

With two Exide 4D deep cycles rated at 320 RC each, one method gives 384 AH and the other 336 AH, for both batteries combined.

This is a 12% to 14% difference. Which formula might be more accurate? The second adds 16. That would make lots of variation in the AH/RC for a small vs a larger system, and that doesn't seem right to me.

Also, I guess in actual application there could be many other factors that will make a 12% initial accuracy difference not much to consider...


"In theory there is no difference between practice and theory. In practice there is."
- Yogi Berra

Any observations or input appreciated.
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Old 12-08-2010, 08:35   #2
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An Exide Nautilus 4D is rated at 160 ah so neither may be right. those calcs are ball park only in my experience. The only way to really know is to physically test it.

To see what i mean do the calcs on ten different batts with published rc & ah/20 hr rates..
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Old 12-08-2010, 09:31   #3
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Peukert's law won't permit Amp-Hour Capacity (20 hr rate) and Reserve Capacity to be exactly correlated.
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Old 12-08-2010, 10:01   #4
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Thanks.
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