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Old Aug 28, 2012, 04:36 PM
everydayflyer is offline
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Southern Pride
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Haralson County GA. USA
Joined Oct 2004
34,852 Posts
True deep cycle Pb batteries have a reserve minutes rating. This is the length that they can supply 25Amps. for from fully charged down to 10.5V under that load which is considered 100% discharged.

My 125Ah deep cycles have a reserve minutes rating of 210 minutes. That is 3-1/2 hours ,thus 125Ah at 20 hour discharge rate becomes 3.5 X 25 = 87.5 Ah at the 3-1/2 hour discharge rate.

Now one should not use more that 50% so 1/2 of 3-1/2 hr. becomes 1-3/4 hr. at 25A discharge rate.

Also consider that cycle life is to the half life. That means that if said battery can be used down to the 50% level 500 cycles in fact at that point it only is only able to supply 50% total of its' rated capacity.

MAx. life is obtained by limiting depth of discharge and recharging as soon as possible after use.

Flooded cells are the least expensive but AGMs last longer under same demands but cost a great deal more. Five years ago my 125Ah flloded ones were $65 each. A 48 Ah AGM I purchased a year and a half ago was just over $200, Excide Yellow Top..

The very best AGMs are sold under the Life Line name. Expect to pay around $400 for a 100 Ah one.

Note: One good part of Excide Yellow Top is that there is a 36 month free replacement warranty. I guess that means use the you no what out of it and hope it fails after two years but sooner than three.

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Last edited by everydayflyer; Aug 28, 2012 at 04:43 PM.
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