question

brett avatar image
brett asked

Is my MPPT shutting down one panel?

I have four LG 350w solar panels connected two at a time to 2 MPPT 150/60 and then into a 5000w inverter. They are charging 4 200ah LiFePo4 batteries. First thing in the morning and up to about 10am all is well. The batteries are reporting 100% are sitting around 13.2v but yet to go into absorption mode. Then something happens. The two panels on the port side are happy taking their full capacity. However on the starboard side about half is being taken. On checking, one panel appears to have been switched off. Is my MPPT faulty?

MPPT Controllers
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1 Answer
JohnC avatar image
JohnC answered ·

Hi Brett. It's most unlikely your mppt is faulty. To test your 'half working' starboard side, try switching off your port panels. If all is well, starboard should bounce back to try to fill the gap. If it doesn't, then to worry..

It's likely your system just can't handle the potential power (full batts?) produced in the sunnier part of the day, and the 'lazier' mppt is backing off first. There's several reasons why one may back off before the other, but in the washup it doesn't matter if the charge V targets are being met overall.

There may be deeper issues with length of Absorb time between mppts, etc., but let's not go there just yet. Unless you force me..

And oh, I only have a single mppt, and if it's backing off by 10am I'm on a good day. If I had 2x I wouldn't care which one took an early siesta.


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