charge controller clipping too much

I have 4-100 watt 12v modules connected to a Xantrex C40 CC that charges 2- 6v batteries in series for a small 12v battery bank at 225A hrs. Usually at mid day with lots of sun the CC usually puts out 20A, for some reason in identical conditions today it is clipping to 7A-9A. I tested the modules by disconnecting one then another and sure enough the CC quickly regulated the output to that 7-9 range, even with fewer modules connected? It's in bulk mode. Why such a drop in output?


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: charge controller clipping too much

    The most obvious question is: does the battery need more than that 7 to 9 Amps?

    Even though the array in total may be capable of putting out 23 Amps, but if the battery SOC is high enough it will not draw full current.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: charge controller clipping too much

    what coot is trying to say is that a charged battery (or nearly charged) will not draw the full power of your pvs as it takes only about what it needs. throw a load on there too like a light bulb and the batteries will still get the same current to them, but the light will get powered to almost directly from the pvs with no charging losses on the light.
  • Mike at Energy CommissionMike at Energy Commission Solar Expert Posts: 50 ✭✭✭✭
    Re: charge controller clipping too much

    thanks guys, after looking at things today, it appears the battery SOC yesterday was such that all is well. I am new to this and kind of surprised how smart that little CC is.
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