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Another Battery Question

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I have a question about deciphering what a battery tag says.

Our truck has 4 Deka 904D batteries as house batteries. These are charged by the truck alternator, but not used- isolated- from the truck batteries.

On the label it says-


Cranking- 1280

CCA- 1050


What would the usable amperage be for these batteries?

They checked out fine, I desulfated them and brought them up to a full charge- 14.4v

The inverter on the truck is a Statpower Prosine 3000 inverter charger.


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Google is your friend. :)




About half way down the page look for the two specs you cited and then follow over to "reserve capacity" which indicates "290". So probably 290 amps for each battery (less any resistance in connectors, cables, etc.).



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Actually.. with a battery like that "reserve capacity" is not measured in amps. It is the reserve capacity in minutes at 80 degrees F to fall below 10.5v @ 25 amps. So you would calculate it at 290rc x .4167 -or- 4.8 hrs @ 25amps = 120ah capacity at the approximate 20 hr rate.


120ah x 4 = 480ah @ 50% = 240 "available" ah's.


....and... 400lbs. :D

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for those sudo deep cycle, the 50% reserve capacity matches 20 hour amp rating. so these are equivalant 145 amp hour.


That's generally a pretty good rule of thumb for a single bank. Across multiple banks of cells it can get you into a little trouble though. In this case about 100ah discrepancy (or 50ah usable)... roughly 20%.

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