Victron Smart Lithium tripping BMS overnight — temperature related?

Been having a similar issue on my narrowboat over the past few weeks. Running a 200Ah Victron Smart Lithium and the BMS keeps tripping somewhere between 2am and 5am — always overnight, never during the day.

My gut says temperature too. The battery is in the bow locker and it's been dropping to around 4-5°C overnight lately. The Victron Smart Lithium has a built-in low-temp cutoff around 5°C if I recall correctly, so that could easily be the culprit if you're in a similar situation.

A few things I've been looking at:

• VictronConnect app — worth checking the battery history log, it'll tell you exactly what triggered the BMS event
• Battery temperature sensor — are you actually monitoring temp or guessing? I added a Victron Smart Battery Sense and it made the data much clearer
• Insulation — I've wrapped my locker in 25mm PIR board and it's made a noticeable difference keeping temps stable overnight

The other possibility is a parasitic load pulling the cells out of balance while everything's quiet. Do you have anything drawing power overnight that wouldn't be obvious — a bilge pump float switch, inverter on standby, anything like that?

What does your Cerbo or MPPT show in the VRM portal around the time it trips? That historical data is usually where the answer hides. Would be curious whether others with land-based setups are seeing the same pattern or if this is more of a boat-specific issue with uninsulated compartments.

Geoff1991 | 847 posts

@SimonJohnson67 classic cold-temperature cutoff behaviour this. Victron Smart Lithium BMS will disconnect at 5°C to protect the cells from damage during charging — and on a narrowboat hull overnight in autumn/winter, bilge temperatures can easily drop that low even if the cabin feels fine.

Few questions: are you on shore power or solar overnight? If something's trying to charge the battery at low temps, that'll trigger it every time.

Worth checking your Victron app history — the BMS disconnect reason is logged and will tell you straight away if it's low-temp charging protection rather than something else entirely.

Quickest fix is a small thermostat-controlled heat mat under or around the battery bank. Keeps cells above the threshold without much draw. Some lads on here swear by insulating the battery box too, makes a surprising difference on steel-hulled boats.

HeathGazer | 412 posts

Good to see you posting @SimonJohnson67, narrowboat setups are exactly what this forum is great for.

@Geoff1991 has the cold cutoff angle covered, so I'll add something slightly different — worth checking whether your bilge or battery compartment has any ventilation gaps that might be drawing in cold air from the canal surface overnight. On my narrowboat I found the temperature at battery level was dropping far more than I expected, even with the stove running.

A cheap STC-1000 temperature logger left near the battery bank overnight will tell you exactly what you're dealing with. Once you've got real data, you can decide whether insulation or a small trickle heater makes more sense.

Also — what firmware version is your Victron BMS running? There were some cutoff threshold tweaks in earlier versions worth checking via the VictronConnect app.

BreezyMechanic | 234 posts

@SimonJohnson67 had almost the exact same pattern with my shepherd's hut setup last winter — that 2–5am window is a dead giveaway, it's when ambient temps hit their lowest point after the heating's been off for hours.

Worth checking whether your battery is positioned near an external wall or floor — mine was sat directly on the timber deck and was losing heat fast. Moved it onto a small wooden platform with 50mm insulation underneath and the overnight trips stopped almost immediately.

Also dig into the Victron app and pull up your battery temperature log — you'll see exactly when it dipped below the 5°C low-temp cutoff threshold. The data tells the whole story without any guesswork.

If insulation alone doesn't crack it, a small self-regulating heat tape around the battery casing is a popular fix in narrowboat circles from what I've read.

EwanChapman | 89 posts

@SimonJohnson67 worth checking whether you've got a small parasitic load slowly draining the battery down to a low-voltage threshold overnight rather than pure temperature cutoff — the two can combine and make diagnosis tricky.

On my shepherd's hut I noticed the BMS was tripping because a 12V fridge compressor was pulling the weakest cell below 2.8V during the coldest part of the night. Adding individual cell monitoring via the Victron app made it immediately obvious which cell was the culprit.

Have you enabled cell balancing history in the Victron Connect app? The BMS logs should tell you whether it's triggering on low-cell-voltage protection or temperature protection — they're different alarm codes. That distinction would really narrow it down before you start throwing solutions at it.