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Bob Sweeney asked

100-50 switches from Bulk to Float too soon

Over the last 2 days the 100-50 solar controller has shifted from bulk charging my 400AHr lithium (BattleBorn) batteries before charging completes. Today the battery bank was at 92% SOC when it switched to float (at 13:11) and so it didn’t fully charge the batteries despite it still being a sunny day. Battery voltage reading from the solar controller shows 14.4v while the BMV-712 shows 13.44v at 13:11 when the switchover occurs. The solar controller is mounted 3 feet away from the battery bank so why would the solar be showing that much of a higher voltage (system installed for over 2 years with no issues, it was running at low loads (100% all day, 95% first thing in the morning) all winter, just started up higher amperage loads (used 76.6 amps last night) when this started to happen, no issues noted during the winter and low loads). Since the solar controller is sensing a much higher voltage it is shifting over to Float mode. The SOC has been very accurate all winter, once in Float the SOC continued to slowly rise up to 94.8 before the sun stopped providing power.

MPPT Controllers
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Alexandra avatar image Alexandra ♦ commented ·

@Bob Sweeney

Have you checked at the mppts terminals what the voltage is with a meter?

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Paul B avatar image Paul B Alexandra ♦ commented ·

The voltage reading at the solar controller reading using your volt meter, should be the same as at your batteries . if not then you need to find out were the bad connection is or the wires from the controller to the battery are to small

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Bob Sweeney answered ·

I used my Fluke multimeter and measured battery voltage at the controller and the battery terminals. Voltages were within 0.1 volts of each other. I removed the wires to the battery and then re-tightened them down. I’ll be watching the controller response however today is cloudy and windy so I’m not getting the amperage out. So far it is staying in Bulk mode, hopefully the problem is solved.

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seb71 avatar image seb71 commented ·

And what was the battery voltage indicated by the solar charger and by the BMV?

Same as measured with the multimeter?

Or you did not look?

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Bob Sweeney avatar image Bob Sweeney seb71 commented ·

The Victron measured voltages were pretty close (~0.1v) of the Fluke. Since then the voltages have started to drift apart, they are 0.25v difference at this time. Had to close things up as we have very high winds and too much blowing grit in the air. I’ll watch remotely for now, will get back on it tomorrow if its not raining as predicted.

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