Friday, Jun 11, 2010 at 10:37
Hello Paul,
I second the other Peter ;)
I don't think it matters much in terms of actual charge being pushed into the battery.
I think the Ah figure has been made configurable so that the controller can display some meaningful SOC percentage depending on how much Ah go through the battery in both ways.
BTW, the specified battery capacity is not a
rock solid constant.
It changes with temperature, and most noteably with battery age.
A perfectly healthy 5 year old battery may only have 80% of the original capacity left.
If it's been abused, then this figure may
well be lower.
In both cases the solar controller isn't going to over or under charge it because the charge termination voltages remain more or less the same regardless of residual battery capacity.
But even these voltage levels can change a little over the life of the battery and could be adjusted by the OP when trying to get maximum service life out of the battery.
But for this to be successful the usage history has to be known, and actual values of internal resistance and float current requirement has to be known (and compared to the same set of properties when the battery was new).
F.e. if the battery was subject to frequent undercharging in the past, then the battery life would be limited by sulphation. If countermeasures aren't taken, this will cause other effects to kick in which shorten battery life even faster.
But if sulphation is detected in time, then this domino effect can be prevented by raising the float voltage to stretch its useful life a bit.
Best, Peter
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