Anyone else had their BMS cut out during cold snaps? Fogstar Drift 100Ah issue

Had a frustrating weekend with my static caravan setup. Temps dropped to around 3°C overnight and my Fogstar Drift 100Ah LiFePO4 just shut itself off completely — BMS low-temp protection kicking in, I assume. Came out Saturday morning to find everything dead: no lights, fridge had warmed up, the lot.

Running it alongside a Victron SmartSolar MPPT 100/30 and a Victron BMV-712 for monitoring. The BMV showed the battery had been sitting at about 60% SOC before cutoff, so it wasn't a low-voltage issue. Just the cold triggering the protection threshold.

I've seen people mention self-heating LiFePO4 cells as a solution but they're a fair bit pricier. For a static van that I use year-round in the UK, I'm wondering if it's worth the upgrade or whether insulating the battery compartment properly would be enough to keep temps above the cutoff point (usually around 0°C for charging, slightly below for discharge).

Has anyone dealt with this practically — foam insulation on the battery box, small heat mat on a thermostat, or just bit the bullet and gone self-heating? Keen to know what's actually worked rather than what looks good on paper.

@GemmaCooper86 oh this brings back memories from last February in my static — exact same scenario, woke up to a dead system at stupid o'clock.

The Drift's BMS cuts charging around 5°C which is actually doing its job properly, lithium cells genuinely hate charging below that. The sneaky bit people miss though is that discharge can still work fine at 3°C, so your loads might run but the solar or hook-up won't top the battery back up.

What sorted me was a simple battery heating pad — I rigged one of those reptile vivarium mats underneath, thermostat-controlled, runs off a tiny trickle. Keeps the cells just warm enough overnight.

Worth checking if your battery is insulated at all — mine was sat on an aluminium shelf which was basically a heat sink drawing cold straight in.

@GemmaCooper86 this happened to me in my motorhome parked up in a Derbyshire layby last winter — brutal. The Drift's low-temp cutoff is doing exactly what it should; charging LiFePO4 below roughly 5°C causes lithium plating and permanently damages the cells.

What saved me was fitting a small self-regulating heat mat underneath the battery — the kind sold for reptile tanks works a treat. Runs off a tiny trickle and keeps the cells just above the threshold.

Longer term, I've since moved to keeping my battery compartment insulated properly with 25mm Celotex offcuts. Made a world of difference. The Fogstar itself is a solid battery — don't write it off over this. It's behaving correctly; the installation just needs adapting for cold-weather use.

FenlandDweller replied:

@GemmaCooper86 Worth knowing that the Drift's low-temp cutoff is actually a feature rather than a fault — charging LiFePO4 below around 5°C can cause lithium plating on the anode which permanently degrades capacity. The BMS is doing its job properly there.

That said, there are practical workarounds. A small self-regulating heating mat wrapped around the battery (the Würth or similar 12V pads work well) keeps the cells above the threshold overnight. Some folk put the battery inside the caravan's insulated storage locker rather than an external bay — makes a surprising difference in a static.

The discharge cutoff is lower than the charge cutoff on most LiFePO4 BMSs, so if you're only drawing power rather than charging, you may have more headroom than you think. Worth checking your specific BMS spec sheet.

Has anyone found a practical workaround for keeping the battery warm enough to prevent the BMS tripping in the first place, rather than just waiting for it to recover? On my narrowboat I've been wondering about wrapping the battery bank in some basic insulation — even just closed-cell foam sheet — to retain whatever ambient heat the engine compartment generates.

Does that actually make a meaningful difference at 3°C, or is it negligible? @FenlandDweller's point about it being a protective feature makes sense, but ideally you'd never trigger it at all.

Also curious whether a small self-regulating heating pad (the kind designed for LiFePO4) is worth the parasitic draw overnight — feels like robbing Peter to pay Paul if your solar input is already low in winter.

FrankPalmer replied:

@GoldenTinker Good question. I've had decent results using a small self-regulating heat mat (the kind sold for reptile tanks or pipe frost protection) wrapped around the lower half of the battery and tucked inside a foam-lined wooden box. The self-regulating element is key — it backs off power draw as the surface warms, so you're not wasting much. Mine pulls maybe 8-12W in earnest cold.

Pair that with a simple temperature-activated plug socket (Inkbird controllers are cheap and reliable) set to kick in around 5°C and you've got a reasonably elegant solution without running anything unnecessarily.

@GemmaCooper86 For a static caravan you've got mains available presumably? Makes the whole thing much simpler than for @VickyFisher's motorhome scenario. Total cost was under £30 for my setup and it's seen me through two winters without a single BMS trip.