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lwitty asked

Did my SmartSolar MPPT 100/30 die?

Have a 400W solar system on my boat with the Smart Solar MPPT 100/30. Been working great since installed in early 2021. Came to the boat today and noticed that the batteries were at 90% through my BMV-700, was expecting them to be at 100%. Looked at the MPPT bluetooth app and saw a discrepancy on the battery voltage - MPPT saying 14.20 (which is the max voltage for the LIFEPO4 battery settings) and the BMV was at 13.20. volt meter verified that the 13.20 was correct as expected.

I then removed the battery (+) wire from the MPPT to the battery. Measured voltage on this was 25V coming out of the MPPT. Was just checking to ensure the fuse had not blown, but was surprised by this voltage. Verified in the app that the battery was indeed set to 12v and not 24v.

I then moved the MPPT output to a different battery bank (AGM) and changed the charging parameters to AGM. App shows MPPT voltage now at 13.8 and battery bank is 12.55.

Anything I am missing here? Seems like the charge controller has failed. Was working fine yesterday, but I did work the battery bank harder than normal yesterday drawing 15-20A for the majority of the day but the solar was pumping in 18-20A for most of the day with no problems.

MPPT SmartSolar
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clintc avatar image clintc commented ·
Without knowing the normal output voltage of your panels, what the sun conditions were like at the time, and what your wiring is like, it's hard to answer your questions. If the BMV is connected closer to the battery terminals than the charge controller, it's not surprising to see a difference in the voltage measured between the two.


As an aside, you mentioned you disconnected the battery +ve terminal from the controller and then measured the output voltage of the controller?

As a rule, charge controllers should never be connected to solar power without any batteries connected. Controllers should always have batteries connected to them first when assembling a system, and disconnected last when disassembling a system.


Regards, Clint

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