I have (2) 100w Renogy solar panels and a 30a 12v wander controller for (4) 12v = 48v Gel battery series system. I’ve been told that I Actually need a 30 amp 48v controller for that type of set up. Can you please advise if this is correct and if so, can you tell me a good controller with those specifications. Thanks!
  • you need to rethink this. 2 x 100 w panels is series yields a mppt of 36v which is not enough to charge a 48v battery bank. The mppt of each '12v' panel is ~16-18v. you would need 4 in series minimum or use different panels.

  • Thanks for the reply. As you can tell, I’m a complete newbie to this type of work. So you’re saying I don’t have enough solar panels? Why can’t I just use two 100w panels for this application? I realize it won’t charge the 48v system as fast as four panels but I’m ok with that. I was told if I put the positive line coming from the controller on battery 1 and the negative on battery 4, that would work. The issue I thought I was having was I only have a 12v controller right now but need a minimum 48v controller to make it work properly. battery’s are 100ah. Look forward to your response...
  • if your batteries are in series then that is a 48v battery (bank).

    Mppt controllers do not step up voltage they do step down high input voltage to battery voltage.

    You would need to find a controller that does step up (if one exists).

  • I’m not following what your saying. (2) 100w Solar panels to controller to (4) 12v 100ah deep cycle batteries in a series. Why is this so difficult? The question I have is. What’s the best controller for this set up?
  • one that can BUCK the low voltage input up to over 48v for charging. My question to you is do they make such a thing. I am not aware of a controller that can increase input voltage to charge. Good luck!

  • please look at the specs of a typical renogy 100w panel

    note at the bottom right "IV-Curve", this is ideal conditions, note that at 22v the panel makes no power, a mppt controller will force this panel to operate ~18v @ the mppt, this point goes much lower when the panels are hot, say down to 16v or even lower. 2 in series connected directly to a 48v battery and there would be no power @ 48v. Also no power at charging voltage which would be up 50v (~60v). They do make BUCK devices that can step up lower voltage to higher voltage but not in a controller that I know of.

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