Trying to help a friend with an issue on his caravan (12V System) but all I have is a multimeter with leads too short to trace wiring (installed by an auto electrician). Symptoms are as soon as the battery is @ 100% the voltage on the inputs climbs to 16.25V and trips out the inverter. Disconnecting the positive output from the MPPT 100/50 solves the issue but the MPPT has been replaced and the symptoms persist. I don’t have a wiring diagram to trace the issue and the only clue I have is disconnecting the negative output from the MPPT does not solve the issue. Also connected to the input is a bluesmart 100/30 230V charger (set to lithium) but switching this off does not fix the overvoltage. When the MPPT is disconndcted the output voltage sits at a more correct 13.49V.
So I suspect a common ground problem but any advice appreciated.
Since the charger is set to lithium i assume that the battery is also lithium. Does it have an integrated BMS? Does the BMS disconnect the battery due to it being full? Are all fuses still good, does the MPPT actually charge the battery not just supplying the load? Otherwise o dont see how the high voltage of the MPPT could trip the inverter.
I have seen similar when a MPPT controller set to auto voltage sense was connected to the panels before the battery and it thought it was a 24v system.
Yes the battery has a BMS so it isn’t being overcharged. The problem is when the BMS switches off the battery charging the voltage jumps up to 16.25V and trips the inverter (which is not a Victron. It’s a 3000W BMPRO.
I don’t think that’s the issue. The MPPT battery type is set to “Smart lithium” and max voltage is set to 13.8V. I also tried “Expert mode” setting voltage parameters directly, based on 4 x 3.45V in series, which is pretty conservative for LiFePO4. The reason I think it’s a ground issue is when I disconnect the ground output from the MPPT that doesn’t bring the voltage down. Only the positive.
What I think is that once the BMS switches there is no “load" on the MPPT so it just goes to the highest voltage it can.
Try reducing the charge voltage, mine is at 14.2 and absorption time to half hour per 100Ah of battery. It then drops back to 13.5v My BMS never switches off.
Thanks but I have adjusted the charge voltages correctly on the VictronConnect app. It isn’t my system or I’d post a screenshot. Max charge voltage is the “Smart Lithium” preset but I’ve also tried “Expert Mode” and set it to 13.8V - so that doesn’t explain why it is jumping to 16.25V.
It could be. Except when the MPPT is disconnected the output reads 13.5V no load not 16.25V. I’ll try to figure out a wiring diagram but I’m pretty sure, shore power, solar and battery are all sharing a common ground. Which means mains neutral is also bonded to battery ground. I’m in Australia and ground is always bonded to neutral on mains.
From my own personal experience, this is exactly the issue. I’ve tried all manor of voltage settings (both in DVCC and in the MPPT) controller, but if the batteries disconnect (either via the BMS or replicated manually via my main bettery isolator) the MPPT voltage spikes. In my case this adversely affects my WiFi router.
I’m planning on not supplying the 12v circuit with sensitive devices directly from the batteries but instead feeding it from an Orion XS set to power supply mode. The only issue I can see with this approach is that the Cerbo GX might not recognise the Orion XS as a power ‘consumer’, in which case it won’t be connected to the Cerbo GX
It is a poorly designed system. The installer was going to use all BMPro gear because that is what the van originally had with a lead acid system. They then changed midstream to Victron because the original BMPro system couldn’t accommodate everything but kept the BMPro inverter. There’s other problems that I won’t go into here because it would just muddy the thread.
I believe the problem is the negative wire from the solar is shorted to ground of the caravan. Whether this is an actual wiring error (I think it is) or a wire worn through to the chassis I don’t know. My mate is seeing a Victron expert somewhere to get it fixed. Once they confirm this is definitely the problem I’ll mark it down as a solution.
