How to know where to stop when you battery is under a load

[PHoganDive]

The electrolysis is what mixes the electrolyte during equalization to eliminate stratification. As the oxygen and hydrogen bubbles rise through the electrolyte, it 'stirs' it up. You don't want too much of it though, so it is current and time limited so as to minimize water loss.

 

[STW]

You could do what I did… a load test. I have 2 6v GC2 210ah batteries in series.. so 210ah.. or approximately 100ah usable.

I put a 7a load (typical load for me) on and measured the voltage every 15 minutes. I also have a shunt that told me how many ah were used. I let the load run for 6 hrs and my voltage was at 11.7 under load. I stopped load and let battery recover. It came back to 12.1v. So that told me I was only getting about 50ah from my batteries… or half of what I should be seeing. I checked and one of my batteries was .3 volts lower than the other. Batteries were getting old, so I replaced.

This is not a perfect test, but it gives me a good idea of what battery SOC is under load, based on my typical load amps.