Electrical – use a 12V battery charge controller to “ballance” two batteries

batterieschargercurrentsolar energy

I have a simple question which drives me crazy and I'm really hesitating to test it, this is why I ask for your opinion.

At home I am using a solar system, using solar panels and a battery. The panels are connected to a charge controller and the charge controller takes care of the battery. So far so good. It's working perfectly and nice since years.

I have still two charge controllers left im my toolbox and there is still a car battery left. Now I was thinking I could utilize that stuff to use abundant power. On sunny days the panels create more electrical current than what I could store in my battery.

My Idea was now to setup a second system with the new battery and the second charge controller. My naive idea is to connect the first battery to the solar input of the second load controller. If the Voltage of the first battery is high enough, the second controller should start loading the second battery. In Theory the (PWM) charge controller should "think" there is a solar panel installed and should load the battery.

After thinking about that for a while I thought that maybe the current of the big battery is a problem. Solar panels are "naturally" limited in electrical current while the battery could maybe kill the charge controller!?

Does someone of you know if charge controllers limit the current inside? I know that there is lot's of ready made battery ballancers out there on the market. But I just want to make use of the spare parts and the second battery.

Thanks in advance

Jack

Best Answer

Generally battery charge controllers have a minimum voltage drop between the input and the charge output to the battery this should be found in the specifications of the charge controller. It is unlikely that you will meet this condition by connecting the input to the pwm charger to the output of the Victron mppt.