Anyone else had their BMS cut out in cold weather?

Woke up yesterday morning to find my Fogstar Drift 100Ah had completely dropped off — inverter showing no battery, the lot. Temps had dipped to about 3°C overnight in my tiny house setup. Once things warmed up a bit it came back fine, no drama.

Turns out the low-temp cutoff on the BMS was doing its job, fair enough. But 3°C seems pretty aggressive for a UK winter — that's practically a normal Tuesday round here. Running a Victron SmartShunt alongside it and the logs confirmed it just flat-out disconnected around 2-3°C.

Has anyone tweaked their low-temp threshold, or is that even possible on the Drift? Alternatively, anyone using a small heat mat or wrap to keep the battery above the cutoff point? Mostly worried about this for emergency backup use — last thing I want is the system dying when I actually need it most.

@RockyTinker yeah, had exactly this on the boat last winter. Fogstar Drift has low-temp charging cutoff built into the BMS — think it kicks in around 5°C to protect the cells. Discharging usually still works fine at that temp, but if anything tried to push charge in overnight (solar controller, shore power etc.) the BMS would have tripped it.

Worth checking whether your charge source was attempting anything in the early hours. On my setup I ended up programming a low-temp cutoff on the Victron MPPT as a belt-and-braces measure so the BMS never actually has to intervene.

Battery should recover fine once it warms up a bit — did yours come back once temperatures rose?

Yeah, this is a classic one — worth checking whether it's the charging cutoff or a full low-temp protection shutdown, as they're slightly different behaviours. @RockyTinker, when it came back on, did it recover immediately once temps rose, or did you need to manually reset anything?

One thing I'd suggest going forward: if your tiny house has any residual heat source overnight (even a small 12v heated blanket wrapped loosely around the battery box), it can keep temps just enough above that threshold. I've got a basic thermostatically-controlled seedling heat mat under mine — cost about a fiver from a garden centre — and it's been solid through two Norfolk winters now.

Also worth logging your overnight temps properly with a cheap sensor so you know exactly when the cutoff triggers. Makes it much easier to dial in a solution.

@RockyTinker worth checking whether your solar controller or any other charge source was attempting to push current into the battery while it was cold — even a small trickle from a MPPT on a frosty morning can trigger that cutoff. The Drift's BMS is doing exactly what it should, protecting the cells from lithium plating damage below around 5°C.

Once temps crept back up it would have reset itself, which sounds like what happened. Going forward, a bit of insulation around the battery makes a surprising difference in a tiny house — even just some rigid foam board. Some folks also set a low-temp charge disconnect on their MPPT directly, so the BMS isn't having to do all the heavy lifting on its own. Belt and braces approach.

Good shout from @NeilAllen there — that's often the culprit. Even a trickle from a solar MPPT on a clear frosty morning can be enough to trigger the BMS protection if the cells are still cold.

One thing worth adding: once the BMS has tripped on low-temp protection, some units won't automatically recover even after temperatures rise. You may need to manually reset it — usually by disconnecting the load side briefly, or in some cases there's a reset procedure in the Fogstar documentation. Worth digging that out if you haven't already.

Also, if this is going to be a recurring issue, a simple temperature-controlled heating mat under or around the battery can work wonders for a tiny house setup. Doesn't take much wattage to keep cells above the threshold overnight.