question

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magnus-fredholm asked

MPPT 75/15 not charging but MPPT 100/20 is

So, I have 2x45W cells connected to an MPPT 100/20 and 1x55W cell connected to an MPPT 75/15, which in turn are charging a LiFePO battery bank. Up until approx. two months ago they were charging just fine, but somewhere around there after a F/W upgrade the 75/15 hardly charges anything. The thing is that when the the cell has a clear los of the sun, the voltage is usually around 19-21V but still it won't charge. The other cells connected to the 100/20 could go as low as 15V but still is charging albeit very little. The 75/15 just sits in "off" mode the whole time.

I've checked all fuses, measured voltages on the cell, after the fuse, on the terminals and it all checks out. Both MPPT's have the same configuration, power reset it, reset to factory defaults and what not.

Does anyone have an idea what causes this situation?

MPPT Controllers
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Alexandra avatar image Alexandra ♦ commented ·
@Magnus Fredholm

If you stop the other mppt from charging does it wake up?

Is the voc of the two panels on the other mppt low enough for the 75/15? Try them to rule out a panel issue.


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magnus-fredholm avatar image magnus-fredholm Alexandra ♦ commented ·
No.


Good idea, I'll try that out!

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magnus-fredholm answered ·

Okay, after some more investigation and switching the panels between the controllers, it seems the panel itself has broken. Case closed.

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