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I have a multiplus II (Cerbo and shunt not yet connected) reading my battery voltage at 40.2 Volts when the voltage on the battery is 52.4V. When charger is enabled, the voltage reads correctly (51.7), but once load applied, the voltage drops down to 40.1V if charge is disabled, voltage reads 40.1V.
Get your multimeter and measure voltage at the battery posts, then measure actual voltage at the MultiPlus DC connection posts. If your multimeter measures anything substantially different at the MultiPlus DC connection posts than the actual measured voltage at the battery posts, then check your DC circuit length and your connections, crimps, fuses/breakers, switches etc - this is usually a case of a loose connection or excessive circuit length creating voltage drop, or an improper fuse/switch/breaker, that sort of thing.
I don't think that it is a matter of the cable length, since it worked for a period. In addition, the cable is just about 1 metre (3 feet approximately). The Charge Controller reads the voltage as per the battery itself. I will however again check the voltage with my multimeter, and also check the DC breaker.
Thanks for the assistance. I have since dumped the DC breaker and put in a new one. Important to note that you also need to ensure that your multimeter is functioning properly (mine had a weak battery which gave wrong readings). So all is well now.
