Charge controller capacity

In an RV application what would be the down side to using 20 or 25 amps of solar panels with a charge controller rated for 15 amps. Will there be damage to the controller when the panels produce more than the charger's rating. I know I will not get the benenft of the extra capacity of the panels but that is OK. My wiring is to small and resistance to high get get the full advantage. I am thinking that while I may be limited to about 15 amps at peak output conditions I will gain during times of less than peak output when my current solar array is puting out only a fraction of it rated maximum out put. So My question is do I need to put a higher rated charge controller on even though the 14 gauge wire is to small to benenfit from the increased current?


  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Charge controller capacity


    The small wire will reduce voltage from the array to the controller, but not current. How your controller will respond to excess current will depend on the controller itself. For example, the Morningstar TriStar controller can handle 130% of its rated current by reducing the output current. Above 130%, it'll disconnect the PV array. This may save the controller, but the batteries won't be recharged. On the other hand, I suspect that there are at least several controllers that wouldn't survive such abuse.

    How about just buying another controller to place between the new PV modules and the batteries? It's usually not a problem to connect several controllers in parallel to charge the same battery bank from different PV arrays.

    Jim / crewzer
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Charge controller capacity

    "It's usually not a problem to connect several controllers in parallel to charge the same battery bank from different PV arrays."

    pay particular attention to what he said as a new controller must have its own pvs running it. you must not share pvs with 2 or more controllers. this means splitting up the pvs you have to run seperate systems with their prospective controllers. from the controllers the battery connections will be the only thing in common between each controller with the proper fuses and disconnects. it sounds complicated, but it's not. the second wire run into another controller will also cut your voltage losses making it a win win scenario.