I’ve had a MPPT 150/35 installed in a solar trailer with a 205W solar panel and 2x 12V 150AHr batteries wired in parallel.
I’ve noticed today (22/01) that back on the 7/01/25 the MPPT charge controller had sudden lost all solar charge for 7 days and magically come back. Weather has been sunny with temps between 35-40 degrees Celsius with only a small afternoon storm on the 7th.
Throughout similar days from when the solar had started coming back again, it couldn’t not get the batteries charged enough to hold my equipment online, as it had no problems in the days before.
Is this something anyone has experience? Is the Controller faulty? There was no firmware updates and no settings I know had changed.
Uploaded screenshot from SolarHistory log pulled in the morning from Victron App.
I would say that the first thing to check is your panel and the wiring from the panel to the MPPT. You mention a storm on the 7th. Has wind or debris damaged the panel or loosened a connector or has water got into a connector or the terminal box or the panel itself. Disconnect the panel from the MPPT and use a multimeter to measure Voc and Isc ( open circuit voltage and short circuit current) and if these are low trace back to the panels. Youtube videos available for measuring these.
You should also try and arrange for a battery charge, your batteries will end up being damaged from under charging. Or try and reduce power consumption until this is sorted.
Strangely, I noticed exactly the same thing just yesterday with one of my 150/35 MPPT devices that had contributed no charge for 4 days, and was showing panel voltage below battery voltage, despite some reasonable (low January) sun on it.
Disconnecting the PV from the controller and I could measure the expected 68v across the circuit (2 x 280w panels in series), reconnect and dropped back to below 24v.
Turned out to be one of the MC4 connectors connecting poorly. Wiggle it about and all would be fine - for a while!
Replaced the connector and crimps, stripping back the cable to new shiny stuff first, and all is good now.
As an update, no visible damage to the panels at all,. Spoke to one of my other technicians and the same thing was said about panel voltage. We measured the open circuit solar voltage and it was measuring 25V when the panel is rated to about 40V from memory.
Replaced panel, and now getting upwards of 37V through the solar, which is a good sign.
Monitoring the battery voltages today and will check if they have been damaged by the under voltage. Hopefully not, but I think they might be.
Obligatory reply of things that might be relevant: This is why you use the correct tools
(Note: i’m not saying this was the case, but just referencing that MC4 connectors are often visually OK, but electrically can be very bad)
If the batteries are Lifepo4, they are probably ok.
Voltages like you are seeing (10.89) are usually indicative of bpm (battery protection mode) and therefore the Voltage is whats leaking through the bms FETs, not the actual pack Voltage.
In bpm, the bms has disconnected the cells from the positive terminal, precisely to prevent any damage, or at least limit the damage, and you have picked up the fault quickly.
