Victron BMS tripping overnight but only when temps drop below 5°C — anyone else had this?

Had exactly this with my Smart Lithium 200Ah bank last winter. The BMS was triggering low-temperature cutoff during the early hours — typically around 3-4am when ambient in my cabin dropped to around 2-3°C.

The issue is that Victron's low-temp cutoff on the Smart Lithium cells defaults to 5°C for charging, which is correct behaviour — charging lithium below that threshold causes lithium plating and permanent capacity loss. The BMS should trip. The question is whether it's tripping on charge protection or discharge protection, which are separate thresholds.

What I'd check first:

• Connect via Bluetooth and look at the BMS alarm history — it'll tell you exactly which protection triggered
• Is anything attempting to charge the battery overnight? A small solar trickle, shore power on float, anything?
• What's your cell temperature sensor reading vs ambient? If the sensor is poorly placed or has a dodgy connection, you can get false readings

In my case, the culprit was the MPPT doing a brief absorption top-up around dawn when irradiance barely ticked above the start threshold — cold cells, charging attempt, BMS trips, everything goes dark.

Fixed it by setting a low-temperature charge cutoff in the MPPT via VE.Smart networking so the charger simply doesn't engage below 5°C rather than letting the BMS do the heavy lifting reactively.

If you're running a third-party BMS rather than Victron's own, the temperature thresholds and hysteresis values are often configurable in the software — worth double-checking what yours is set to, as some ship with overly conservative defaults.

What battery chemistry and BMS are you actually running? That'll help narrow

@Paddy yes, classic low-temp cutoff behaviour — lithium really doesn't like being charged below around 5°C, and the BMS is doing exactly what it should honestly.

My shepherd's hut setup had identical issues last February. Fixed it two ways:

1. Heating mat underneath the battery (thermostatically controlled, kicks in around 8°C)
2. Set a low-temp charge disconnect rule in VictronConnect so the MPPT backs off before the BMS even needs to intervene

The second one's underrated — stops the BMS tripping entirely rather than recovering from a cutoff, which can be a faff in the early hours.

Worth checking whether it's charging that's triggering it or just discharge — Victron Smart Lithium BMS distinguishes between the two. If it's discharge cutoff at those temps that's a different conversation.

What's your battery enclosure situation? Insulation makes a massive difference.

@Paddy this caught me out badly my first winter with the static. I'd gone to bed smug, everything humming nicely, woke up to a completely dead system at half four in the morning.

What solved it for me was fitting a Victron Battery Protect alongside a small thermostatically controlled heat mat directly under the battery bank — set to kick in around 7°C so the cells never actually reach the cutoff threshold. The mat draws very little, and the insulated battery box does the rest.

Worth also checking your Venus OS logs if you're running a GX device — the timestamp data showing exactly when the BMS tripped helped me dial in the thermostat setting properly rather than just guessing.

The other thing nobody mentions: even a modest SOC drop in the evening makes the low-temp cutoff trigger earlier the following morning. Keep them topped up going into a cold night.

Victron's low-temp charge protection kicks in at 5°C by default but you can tweak the threshold in VictronConnect — though I'd argue don't, because charging cold LiFePO4 is genuinely how you wreck cells permanently.

Real fix: a small self-regulating heat mat on the battery bank, wired to a thermostat set to kick in around 8°C — mine runs off a tiny 12V feed and draws sod-all. Fogstar cells have decent cold tolerance but even they'll thank you for it.

Also worth checking: is your BMS actually triggering on charge low-temp, or discharge low-temp? Two very different problems. Pull the VRM logs if you've got a Cerbo — the timestamp data'll tell you exactly which protection fired and why, rather than guessing at 3am in your pants.

@FormerCop worth noting that tweaking that threshold is a bit of a double-edged sword — you're essentially telling the BMS to trust you more than the chemistry. I'd be cautious about that on a boat especially, where you can't always monitor things closely.

What actually sorted it for me was adding a small 12V heat mat under the battery bank, wired through a simple thermostat relay set to kick in around 7°C. Keeps the cells above the cutoff threshold without babying the BMS settings. Picked up the thermostat controller off Amazon for about £12 — nothing glamorous but it's been rock solid through two winters now.

The other thing worth checking: is the BMS temperature sensor actually reading cell temp or ambient? On some installs it ends up measuring the wrong thing entirely.