Hey all, I’ve recently installed my first Victron system on an RV. Components in question here are the MultiPlus II 2x120 24V, SmartShunt, and Cerbo GX. The way I’ve set everything up, I thought should be correct, but I’m getting some odd behavior. Because it’s an RV, there is a 12V DC system in addition to the MultiPlus outputs. I have 2 batteries wired to the battery side of the shunt, and system side of the shunt goes to the MultiPlus, DC system, and all the Victron components; that is to say, absolutely no load bypasses the shunt, it should see everything. Because of the DC loads, I have the Cerbo set to “has DC system”.
When the MultiPlus is off, it appears that the shunt registers DC loads as charging the battery, not drawing from it. The little dots on the overview graphic appear moving towards the battery, and the amperage readout on the battery shows positive while on the “DC system” amps show negative.
When the generator is running and the MultiPlus is charging the battery, it seems to mostly behave normally, but the DC system amp readout will bounce between positive and negative.
I’m not sure if this is the root cause or not, but the State of Charge readout is entirely inaccurate, too. I’ve just done my first trip with this system. I had the batteries fully charged before leaving, sync’d the shunt to 100%, and left for the trip. My first night, batteries completely died, to the point nothing would power on even briefly, the 24V battery bank was registering under 10V, yet the shunt still read 82% SoC. Throughout the rest of the trip, I had low batteries at various times, setting off the alarm on the MultiPlus, etc. And the shunt would read <20V while still showing 100% SoC. It also appears this is impacting charging, as the batteries were under 20V and yet the MultiPlus was showing the charging state as “float” within 10 minutes of starting the generator.
Needless to say, I’m rather confused. Any tips would be greatly appreciated!
EDIT: Pictures of installation for wiring purposed added below, thanks @Matthias Lange - DE
