[RE-wrenches] Best Off-Grid Equalize Charging Method

[Jeff Yago]

I know this has come up before but wanted to see if anything new available. 

Unlike on-grid battery-based systems, off-grid systems require a different equalize charging strategy to reduce generator run-time and save fuel. The problem arises when you have a large battery bank and a not so large solar array. 

You can first run the generator early in the morning at a high bulk rate to shove as much charge into the battery as possible, then take over charging with the solar charge controller set for equalize charge and hope you have enough sun-hours and current to take the generator-charged batteries past their normal voltage and start gassing, 

OR, 

You can do the reverse and solar charge all day and then at the end of the day use the generator with the inverter set for equalize charge and continue charging while hoping this will not require too many hours of fuel usage. 


Of course the size of the solar array verses the size of the battery bank may favor one method over the other, but are there any actual tests or studies that make one method always the better choice?

I have found that small arrays have a real hard problem ever getting a large battery fully charged, let alone provide an equalize voltage for several hours, yet I have also found most inverters supplied by a generator tend to back-off the charging current as soon as the battery nears a fully charged state then tries to stop the generator. I also have found that some deep-cycle batteries sold for solar applications require charging voltages and re-charging times that are almost impossible to achieve unless you have grid power available.

Any documented testing out there?

Thanks,

Jeff Yago




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