Anyone else running 200Ah LiFePO4 in a motorhome and finding BMS cut-off a nightmare in cold weather?

Picked up a 200Ah Fogstar Drift last spring and overall I've been dead impressed — solid build, good comms via the app. But now we're heading into winter and I'm noticing the BMS is tripping out on low-temperature protection around 3–4°C. Woke up on a site in the Peak District last week to a completely dead 12V system at 6am, -1°C overnight. Van had no heating because the Webasto pulls from the leisure bank. Not ideal.

The Drift's rated down to 0°C discharge, so it's right on the edge in real UK winter conditions. I've seen people insulate the battery box with Armaflex and even stick a small heat mat on a thermostat underneath — something like a 10W reptile mat wired into a separate always-on circuit. Has anyone actually done this? Wondering what the lowest sustained temperature you've seen inside a well-insulated underfloor box is compared to ambient, and whether 10W is genuinely enough or if I need to go bigger.

Running a Victron SmartShunt and MPPT 100/30 alongside it — the Victron kit all talks nicely to the Fogstar via VE.Smart networking so I can see exactly what's happening. The data shows the BMS cut discharge at 2.8°C cell temp, which matches the spec. Just need a practical solution before the next trip up to Scotland in January.

@MasterCamper I've had exactly this on my cabin setup with a 200Ah LiFePO4 — the BMS low-temp cutoff is doing its job but it's frustrating when you just need power.

Few things worth looking at:

• Insulate the battery compartment — even basic foam board makes a surprising difference
• Self-heating BMS models exist (Fogstar Drift Plus has it I believe?) — worth checking if yours has that option
• Does your Victron MPPT have a low-temp charge cutoff configured? That might be triggering before the BMS even kicks in

The real question is what temperatures are you actually seeing inside the compartment vs ambient? Sometimes it's not as bad as you'd think once the vehicle's been running a bit. A cheap temperature probe on the battery itself would tell you a lot.

@MasterCamper This took me by surprise too when I first set up my garden office system over winter. What actually solved it for me was fitting a small self-regulating heat mat directly against the cells — draws next to nothing overnight but keeps the pack above that critical threshold. Worth checking whether your Fogstar app is logging the actual cell temperatures vs ambient, because there's often a bigger gap than you'd expect inside a motorhome when it's been parked up overnight.

The other angle nobody mentions: charge source matters. My Victron MPPT has a low-temp charge disconnect setting that plays nicely alongside the BMS rather than fighting it — meant fewer nuisance trips once I dialled that in properly.

Been running a 200Ah LiFePO4 in my motorhome for two winters now — same issue caught me out first season. What sorted it was wrapping the battery in a bit of closed-cell foam insulation and relying on the ambient heat from the van interior overnight. Battery rarely drops below 5°C now even when it's freezing outside.

Also worth checking your Fogstar app — there's a low temp charge cutoff setting. I adjusted my Victron MPPT to stop charging attempts until the battery comms confirm it's above the threshold. Took a bit of fiddling but it's been rock solid since.

The BMS is doing exactly what it should — charging a cold LiFePO4 properly damages the cells. Keep it warm rather than fight the protection.

@MasterCamper One thing worth adding to what others have said — I'd strongly recommend keeping an eye on your charging sources during cold snaps. Even if your battery survives the night without tripping, your solar controller or B2B charger may still attempt to push charge into a cold pack first thing in the morning before it's warmed up sufficiently. Most LiFePO4 cells really don't want to be charged below about 5°C.

If your Fogstar Drift is connected via Bluetooth, set yourself an alert for low temperature so you're not caught off guard. Also worth checking whether your habitation area heat bleeds through to wherever the battery is mounted — even a small amount of warmth overnight can make a real difference. Mine sits in a locker just behind the cab and retains enough heat from the living space to stay above the cutoff threshold most nights.

Something that hasn't been mentioned yet — if you're running an EV charger off your setup (I charge a Leaf occasionally from mine), the BMS cut-off mid-session is particularly annoying because some chargers don't recover gracefully after a sudden power drop.

Worth checking whether your Fogstar app lets you set a low-temp charge inhibit threshold rather than waiting for a hard BMS trip. The Drift has configurable parameters if I recall — you can essentially tell it to refuse charging below, say, 5°C rather than having the BMS slam the door unexpectedly.

A battery heating pad wired to a small thermostat controller (picked one up off Amazon for about £15) keeps mine above the critical threshold overnight without much parasitic draw. Sorted the cold-weather nonsense completely on my setup.

@MasterCamper this one caught me out badly during the Beast from the East a few years back — woke up to a completely dead system because the BMS had done exactly what it's supposed to do and I'd not planned for it at all.

What transformed my setup was adding a small self-regulating heating pad wrapped around the battery — the kind used for reptile tanks, ironically. Runs off a tiny draw and keeps the cells just above that critical threshold overnight.

Worth checking your Fogstar app for the actual cell temps rather than ambient — there's often a bigger gap than you'd expect once you factor in wind chill against the habitation floor. My cells were reading 4°C when the interior felt perfectly mild.

The BMS is protecting your investment, not failing you — it just needs a bit of help through British winters.

@MasterCamper Worth looking into a self-heating LiFePO4 if you plan on upgrading down the line, but for now a practical workaround is to keep a small 12V heating pad (the sort sold for reptile tanks, oddly enough) tucked against the battery casing overnight. Draws minimal current and keeps the cells just above that critical threshold. I've been doing this with my setup since last November and haven't had a single BMS trip. Obviously make sure there's adequate ventilation and nothing's touching terminals. Cheap fix until the weather improves.