Quote:
Originally Posted by Ronn
Where does the 50% magic number come from, neither of these charts?
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I comes from the same place that the sun never shines as every other arbitrary "rule of thumb". If the argument is that 80% discharge cuts life in half compared to 50% discharge, then I say you should never (on pain of death
) ever exceed 30% discharge, because 50% discharge cuts life in half compared to 30%.
The chart is for discharging to that depth on every cycle. A single discharge to 80% instead of a user's usual 50% (for example), doesn't cut life in half. Time matters, too, not just discharge depth, and so does discharge rate, so you can't predict the life based entirely on the discharge versus cycles chart. The chart just illustrates one relationship in the several factors that affect battery life.
My thinking is discharge as much as you need to, but recharge at the first opportunity. The tolerable life (in cycles) will depend on the application; while thousands of cycles sounds nice, if you are only going to use 500 cycles in the couple of decades that you own an RV, why would it matter if the battery could last longer?