Victron Smart Lithium acting up after cold snap last week — BMS cutting out randomly

Seen this exact behaviour on my own setup last winter. The Victron Smart Lithium cells have a low-temp cutoff that kicks in well before you'd expect — something like 5°C for charging, if I recall correctly — and if your BMS is seeing any cell-level temperature variation, it can get quite trigger-happy even when ambient feels "fine."

A few things worth checking:

• Cell temperature sensors — are they actually making good contact with the cells, or have the mounting clips shifted? Thermal paste helps enormously here.
• Firmware on the BMS — Victron pushed some updates last year that changed how aggressively the low-temp protection responds. Worth connecting via Bluetooth and checking you're current.
• State of charge going into the cold snap — cells at low SoC are more vulnerable to BMS cutouts because internal resistance spikes in the cold, which can trigger overcurrent protection even on modest loads.

On my system I've got the batteries in an insulated enclosure with a small reptile heat mat (thermostat-controlled, obviously) that kicks in below 3°C. Sorted the random cutouts almost entirely.

One other thought — if you're trying to charge from solar during a cold morning and the cells haven't warmed up yet, the Victron MPPT will just get disconnected repeatedly. You can configure a low-temp charge cutoff in VictronConnect, which at least makes the behaviour intentional rather than seemingly random.

What temperatures were you actually seeing inside the battery compartment? And are you running the Smart BMS 12/200 or the larger VE.Bus BMS? That changes what diagnostics are available to you.

Chippy45 | 847 posts

@ThistleTel is spot on about the 5°C threshold — worth adding that it's the cell temperature being measured, not ambient. So even if your shed or van feels relatively mild, the cells themselves can be sitting colder than you'd think, especially first thing in the morning before any charge current has warmed them slightly.

One thing worth checking in the Victron Connect app is your battery temperature readout history — gives you a clearer picture of exactly when the BMS is tripping. If you're regularly hitting that threshold, a self-heating battery blanket wrapped around the bank and controlled via a simple thermostat is a fairly tidy fix without breaking the bank. Some folks also use a small trickle from a DC-DC charger to gently warm cells before the main charge cycle kicks in.

ExFirefighter | 312 posts

Worth asking the obvious question first — have you actually checked what your cell temps are reading in the Victron app when the cutoff happens? Because there's a difference between the BMS cutting out because of low cell temp, and cutting out for another reason entirely.

On my static caravan setup I had what looked like a temperature cutoff but turned out to be a loose cell interconnect causing a voltage imbalance that tripped the BMS. Looked identical in terms of symptoms.

What does the BMS event log show? That'll tell you straight away whether it's logging a low-temp event or something else. If it is genuinely temperature-related, the fix is insulation or a small heater mat — but diagnose first before spending money.

ExFirefighter11 | 312 posts

Following on from what @Chippy45 said about cell temperature — this caught me out on the shepherd's hut build last February. Ambient outside was only -3°C but the battery box, tucked under the chassis with zero insulation, was sitting at 2°C when I checked the Victron Connect app. The BMS was doing exactly what it should, just not what I wanted.

Ended up wrapping the battery in 25mm Kingspan offcuts and fitting a small self-regulating heat trace cable — the kind plumbers use on pipes. Draws maybe 15–20W but keeps the cells above 8°C even overnight.

Worth pulling the historical data from Victron Connect — it logs cell temps with timestamps. You'll see exactly when the cutoffs happened and whether it correlates with overnight lows.

PanelSteve | 1,203 posts

Right, so nobody's going to mention the real problem here — you've got a battery that's basically gone full diva on you. "Ooh, it's a bit nippy, I shan't be accepting any charge today, thank you very much."

Mine did exactly the same thing last