How do solar charge controllers work?

I want to get a 5 watt 12 volt solar battery charger but I want to clear up my understanding of how they work before I get one.  

FIrst:  The panel comes with a charge controller.  It says it cuts in at 13 volts.  What does that mean?  It starts charging once the battery drops to 13 volts?  That can't be it because 12 volt batteries range in voltage from 11.9 to 12.6 volts (charged/discharged).  

Second:  "12 volt panels" output more than 12 volts right?: because batteries need 14.8 volts to charge.   I think they call it a 12 volt volt panel because it charges 12 volt batteries and not because it outputs 12 volts.  It must really output 22 volts and the charge controller steps it down to 14.8 volts.

Thanks for the help

Jacob 

RheanF1 year ago

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Thank for good explaining. I can understand for what i dont know?

you are somewhat right about the voltage coming from the panel. What the charge controller does is monitor and regulate the voltage going into the battery. the charge controller wont let any voltage flow into the battery unless it is higher than the mininum voltage allowed for that specific controller. If is says it " cuts in" at 13 volts it probably means it wont charge the battery unless there is at least 13 volts of input.
I'm afraid it can mean different things to different people. In the simplest chargers, a linear regulator feeds the battery a limited current at 2.2 V/ cell. The input to the circuit HAS to be more than 13 volts. When the current drops to close to zero, it is charged, and ideally should drop to trickle charging voltages.

In other circuits, switch-mode circuits boost the output to 13 volts etc etc.

In the BEST circuits, switch mode circuits load the cell in its maximum power point mode, which is a function of the light on the cell, and the buck or boost the output volts to 13V.

Steve