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SmartSolar 150/70 not charging and showing different batt voltage than smartshunt

Having issues with a system that I installed for a customer recently that I simply cannot figure out. The smartsolar 150/70 provided full production the first 24 hours that it was installed. In subsequent days, solar production dropped (day 1 = 590wh, day 4 = 20wh). Location remained pretty much constant, with roughly equal sun each day.

At the same time, battery voltage/state of charge was gradually going DOWN, according to the smartshunt. This confirmed that the smartsolar was not producing PV power, while power was being consumed from the battery bank. During this same time, there was a widening discrepancy between the battery voltage being read by the smart shunt and the battery voltage being read by the charge controller. At one point, the solar controller read 13.49v vs. smartshunt 13.10v. A day later, the solar controller read 13.49 while the smartshunt read 11.95v (at the same time the smartshunt read 100% state of charge, which made no sense).

Pretty lost here - I'm not on site anymore, which complicates the troubleshooting, but would love any suggestions. I verified that settings were correct after installing everything in the system.

MPPT ControllersSmartShunt
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wkirby answered ·

The one thing that stands out the most is the Voltage discrepancy between the MPPT and the shunt.
It would seem that the MPPT is happily sitting at its target float Voltage. If this is true, then it suggests that the MPPT is disconnected form the battery or there is a high impedance path between the MPPT and the battery somehow. A loose connection or circuit protection device has opened.
Is it possible to read the what Voltage the MPPT reports at night when there is not PV? It'll either be the same as the shunt reading or it will be 0V. Perhaps the MPPT will disappear from the system at night because it is only being powered by PV.

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nyyankees588 avatar image nyyankees588 commented ·
That was one of my thoughts as well. No breakers are tripped and no connections should be loose, as the issue started occurring the day after I finished connecting/updating the system. I'll have the owner report back on the PV battery voltage @ night.
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nyyankees588 avatar image nyyankees588 commented ·

The owner was able to verify this last night - at night, with no sunlight, solar charge controller read 13.27v battery voltage. So it appears that there is no disconnect between the charge controller and batteries. Still very uncertain as to what is causing this issue... any other ideas floating around out there?

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