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When parking boat in a no load scenario, it would be good to solar charge LiFePo4 only up to only 80% SOC. This is good for battery life and when starting engine and leaving dock 100% is reached pretty soon anyway. Can this be accomplished with mentioned products?
yes you can just set the absorbtion voltage lower on the MPPT charge controller - exact voltage would depend on battery voltage and chemistry...
If you're not too fussed about how exact the 80% is, +1 to adev's suggestion. Getting the (and trusting) the 80% value on a BMV will require effort in setting up and possibly ongoing effort as well.
As far as I understand it, the voltage must be very low to stop charging completely, otherwise 100% SOC will be reached eventually. My idea was to use SOC instead of voltage. (well synchronized periodically by using shore power).
I've read the attached link, and think that its consistent with what we're saying; the first answer in the link I think could also have been worded better.
Some background - for any given battery (and this is different between batteries, even in the same manufacturing batch), there is a voltage level that would equate to 100% SOC. When the battery is charged to this point, you would get the nameplate capacity (xxx amp-hours) out of it if you were to completely flatten the battery, in the conditions given by the manufacturer, and everything else in the environment being identical.
For all practical purposes, you would not be able to (or even want to) precisely measure this voltage. You rely on the typical charging voltage given to you by the manufacturer.
The point of the above background is that if you were to charge to a voltage level below the typical charging voltage, you would reach XX% SOC, where XX < 100. This is essentially what the 2nd answer is saying in the link.
In the 1st answer, when they say "the charging time takes longer", it means that it takes longer to charge to YY% SOC, where YY < 100. Not that the charging time to 100% SOC takes longer. When you charge at a lower voltage, you will never reach 100% SOC.
FWIW, I believe the "word" is that 50% SOC is better for longevity. But obviously there's a tradeoff between longevity and practical use of the battery.
