Quote:
Originally Posted by Don Rotolo
Please do not confuse charge retention with capacity retention.
Charge loss is reversible; we generally re-charge batteries after each match.
Capacity loss is irreversible, it is the permanent loss of (some of) the ability to re-charge (or more accurately to deliver that energy back to the load)
A charge loss of 20% over 6 months is typical for lead-acid chemistry, no surprises there. For capacity loss, focus instead on "life expectancy" on that same data sheet.
IF you want to prevent significant capacity loss, keep the battery charged. Industry standard is 3 months on the shelf before it needs a recharge. We try to use that as a maximum.
The greatest factor of permanent capacity loss is allowing the battery to sit in a discharged condition. This allows the formation of 'hard' lead sulphate crystals which cannot be reversed by charging. As the sulphur comes out of the electrolyte, it loses effectiveness and the crystals 'clog' the lead oxide reducing the ability of the chemical reaction to occur, both reducing capacity.
Anyhow, to the original question: the charger can deliver 6 amps, it takes about 1.5 hours to recharge a battery, so we've used 9 Amp-hours as a rough estimate, about 50% of the battery capacity.
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ah, correct, I misunderstood their terminology. So their 20% loss is due to their internal ESR discharging it on the shelf and not referring to their internal impedance growth (your 'clogging') where the electrons remain lithiated in the anode/cathode material.
My main interest in knowing the average energy was to see if a) this battery is overkill and b) if something like an ultracapacitor stack could replace it since there is no significant capacity fade associated with a UC stack (among other benefits).