I have a 3 X 18650 battery set with bms. I would like this to be charged using a 12 volt solar panel which outputs anywhere from 15 to 20 volts. the BMS has a max voltage rating of 12.8 volts.
I was wondering if it would be possible to use a voltage regulator like 7812 to regulate the output of the solar panel to 12 volts so that it could charge the batteries?
I do not want to use a solar charge controller if it can be avoided.