question

bkuethen avatar image
bkuethen asked

SmartSolar won’t charge while batteries under load

Hi,


I have a 1200 watt solar array connected to an 150/35 MPPT Smart Solar charger. That’s connected to a Lynx distributor with a 12v/3000w MultiPlus and two 6v 220Ah deep cycle cells in series (110Ah/1320Wh capacity).

Under normal operation I’m getting 450 watts from the charge controller (limited to 35amps of charging for the sake of the batteries).


The issue starts when I put the MultiPlus under load (~1500 watts). When that happens the charge controller drops the wattage to a few watts. It jumps around a bit but isn’t near what it was before the MultiPlus load. Why is that? I was hoping the solar array would offset some of the usage so I’d only be using 1,050 watt hours from the batteries.

Is there a configuration/setting that would allow the charge controller to continue to supply power while the MultiPlus is under a heavy load?

This doesn’t happen when the MultiPlus is under a light load (<~300 watts).

MPPT Controllers
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1 Answer
Jesse avatar image
Jesse answered ·

I expect you're experiencing DC ripple generated by your inverter. The MPPT is trying to optimise input voltage but if the output varies too much I guess it gets confused and gives up?! I've previously had the exact same problem in a similar sized setup though sadly I never got around to measuring how much ripple was there - maybe you can check yours for me. (Well described on this site - just need a multimeter in AC mode applied to the DC terminals of the inverter)

I cured the issue with a complete overhaul - I'm not sure which change had the largest impact but they all probably helped. Bigger capacity battery bank. Separate wire path for the MPPT's and the inverter to the batteries - for both positive and negative - nothing shared. Thicker wires!

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