Anyone else's Victron MultiPlus throw a wobbler when the static gets cold?

Mine's a MultiPlus-II 24/3000 and every winter it starts rejecting the bulk charge like it's had a bad pint — sits there blinking amber until I give the van a kick (literally).

Running Fogstar Drift 24V LiFePO4, Cerbo GX, and a 400W Renogy array on the roof, so it's not exactly a budget setup held together with gaffer tape.

Wondering if it's a temperature compensation issue or just the Victron being dramatic — anyone tweaked the low temp cutoff settings in VictronConnect to sort this?

@LutonBuild mine did the same until I realised the MultiPlus was basically going into a sulk because the Fogstar cells were reading colder than the configured low-temp cutoff — turns out temperature compensation on the charge voltage was the culprit, not the beer.

ThistleWalker | Posts: 847 | Location: Scottish Borders

@LutonBuild worth checking your BMS communication wiring before anything else — I had almost identical symptoms with a cold-weather bulk rejection and it turned out my VE.Bus cable had a slightly dodgy crimp that only caused grief below about 5°C (metal contracts, connection goes intermittent, MultiPlus throws a wobbly).

Also, what's your charge current set to in VEConfigure? Fogstar Drift cells have a lower recommended charge rate at low temps and if the BMS is throttling back but the MultiPlus isn't seeing that properly via DVCC, you can get this weird rejection loop.

Stick a thermometer near the battery bank overnight — if you're seeing anything below 5°C the BMS may simply be doing its job protecting the cells from cold charging damage. That's actually the correct behaviour, frustrating as it is.

Hey @LutonBuild — worth checking your VE.Bus cable connections first, cold contracting the connector slightly can cause intermittent comms issues that'll make it strop exactly like you're describing. Also, what's your battery temp sensor situation? If the MultiPlus doesn't know the pack is cold, it'll still try pushing charge at room-temp parameters and the BMS on the Fogstar will rightly tell it to do one. Chuck a BMV-712 or SmartShunt in if you haven't already — the temp compensation alone has sorted similar grief for a few people I know running LiFePO4 in unheated spaces over winter. The kick fixing it temporarily suggests a loose connection somewhere rather than anything catastrophic, mind. 🔧

@LutonBuild cold weather + Fogstar + MultiPlus-II is basically a holy trinity of "who blinks first" — your BMS is probably throttling charge current because the cells are below 5°C and the MultiPlus interprets that as a fault rather than a polite refusal, so check your Charge current limit in VE.Configure and set a proper low-temp cutoff in the BMS rather than letting them argue like a divorced couple at Christmas.

MeadowCarl | Posts: 312 | Location: Worcestershire

@LutonBuild one thing nobody's mentioned yet — have you checked your battery temperature sensor is actually seated properly? The MultiPlus-II will get very conservative with bulk charging if it thinks the batteries are colder than they are, or if the sensor's reading is erratic. Worth diving into VictronConnect and watching the live temperature readout whilst the van's sitting cold overnight. Also, what's your low temperature cutoff set to in the Fogstar BMS? If it's set aggressively it'll pull the charge enable signal before the MultiPlus has really got going, which looks exactly like what you're describing. A kick presumably joggling a loose connection somewhere too, so don't rule out what @ShaunButler said either.