Yes, have that graph (I think the left arrow s/b pointing at the 10%
number). See that if the graph were continued to the ordinate it would
asymptotically approach infinity, meaning that for very low DOD it doesn't
matter how many cycles a battery undergoes.
Thus, it perhaps doesn't matter if the battery is retained on float charge
vs. getting recharged periodically from a very low DOD.
Is sulphation an issue under constant float voltage conditions?
JoeS.
> From: Eric <ewdysar@yahoo.
> Reply-To: <electricboats@
> Date: Fri, 01 Jan 2010 21:25:36 -0000
> To: <electricboats@
> Subject: [Electric Boats] Re: AGM Battery: To Float Or Not To Float
>
> Joe,
>
> Keep in mind that the number of cycles is dependent on the depth of discharge
> of that cycle. With lead acid batteries, a deep cycle battery may have a
> lifespan of more than 10,000 cycles with a shallow (5%) DOD, but only some
> hundreds of cycles of life at deeper levels (>70% DOD). I'm not sure that a
> constant trickle charge ages the battery any slower than repeated cycles of
> less than 1% DOD.
>
> A file was posted to this group just over a week ago named "batteryLIFE.
> that illustrates this concept graphically.
>
> Fair winds,
> Eric
>
> --- In electricboats@
>>
>> The Question:
>>
>> "For battery LONGEVITY, is it preferable to have the battery absorb every
>> last bit of energy and sit there fully charged with an external float
>> charger (set to, e.g., 13.2v at 70degF), or is simply turning off everything
>> when float current gets below a certain point preferable?"
>>
>>> From: James Graham <osirissail@
>>>
>>> Battery life is measured in "cycles" not hours, days or years. Each time
>>> the
>>> battery is allowed to discharge and then a battery charger kicks in to
>>> re-charge the battery that is a cycle...
>>> - - Constantly "on" charge battery charges not only keep the battery topped
>>> off but they will provide the electricity to run the other equipment
>>
>> Thank you for emphasizing that the measure of longevity is "number of
>> cycles", even if those cycles are extremely shallow DOD and last only a few
>> seconds...
>
>
>
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