In my case, the three stooges didn't install a charge controller. Excess charge would be 'wasted' or would boil out the batteries if not monitored closely. A better use for me would have been to heat my hot water.
I was 100% off grid btw. I had a water tank that was heated by the wood stove in winter or a solar rooftop heater in summer with a switch to redirect water flow as necessary. Unfortunately, the three stooges didn't install a pump, so the rooftop hot water never cycled to the water tank to stay warm -unless I manually drained it first - because the tank was below the solar heater, and not arranged for convection(hot rises/cold sinks) I could have run-out the unheated water in the garden, but that much water ate up my filters. (I could write a book on 'don'ts') The HW worked if you used it directly from the solar collector, but hot water in the morning was not a possibility, it was more like lukewarm. My water source was gravity fed from a spring on the mountain behind the house btw and was triple filtered. Water pressure was 100% reliant on gravity-zero pumps in the system.