Anyone else had their BMS throw a tantrum mid-winter and kill their whole setup?

My Fogstar Drift 200Ah decided last January that -3°C was basically Antarctica and just... stopped. Flat. Nothing. The low-temp cutoff kicked in overnight and I woke up in my static caravan with no heating, no kettle, and absolutely no will to live.

I've got a Victron SmartShunt keeping an eye on things and I could see the battery had been sitting at a perfectly healthy 52V before the BMS threw its toys out. Frustrating doesn't cover it. Wondering whether a self-heating LiFePO4 pack is actually worth the premium or whether insulating the battery box properly does the same job for a tenner.

Has anyone found a sweet spot — like a minimum enclosure temp you aim for, or a specific heating mat wattage that keeps things happy without draining your whole bank just to protect your whole bank? Feels like a very circular problem.

IslandDweller | Posts: 847 | Orkney

@HeatherWalker Oh, I feel this deeply. Living up here, low-temp cutoffs are basically a seasonal ritual for me.

What sorted it for me was wrapping the battery bank in closed-cell foam and tucking a small 12V heating mat underneath, controlled by a simple thermostat probe set to kick in around 5°C. Costs pennies to run overnight and keeps everything above the cutoff threshold.

Worth checking your BMS settings too - some units let you adjust the low-temp cutoff point if you're using LiFePO4, which handles cold better than other lithium chemistries anyway. The Fogstar Drift should be fine to around 0°C for discharge at least.

Did it recover fully once temperatures rose, or are you seeing any capacity loss now? Sometimes a sudden cutoff like that can mask an underlying cell imbalance worth investigating.

NeilEdwards | Posts: 134 | Array

Slightly different angle on this — has anyone looked at whether EV charging demand is making the low-temp issue worse? I'm trying to run a basic overnight trickle charge for my car off my setup, and I'm wondering if that extra load is basically draining the battery faster overnight, meaning it hits low-temp cutoff earlier and at a lower SOC than it otherwise would.

The Fogstar Drift BMS specs suggest it cuts off around 0°C for discharge — does anyone know if there's a meaningful difference between the Drift and something like a Fogstar Volt in terms of cold weather tolerance? Trying to decide whether upgrading the battery or adding some form of battery insulation box is the smarter move before next winter hits.

HiluxConvert | Posts: 312 | Array

Had almost the identical situation in my static last February. Woke up at 6am, Victron Cerbo showing a big fat nothing from the battery bank — Fogstar had tripped the low-temp cutoff at around -2°C.

What saved me eventually was wrapping the battery compartment with rigid PIR insulation board and adding a small 20W heat mat on a simple thermostat, triggered at 2°C. The thermal mass of the cells themselves holds enough warmth overnight once you stop the compartment venting cold air freely.

The real lesson though — my Victron MPPT was still trying to push charge into a battery that was refusing it. Worth checking your charger handles that gracefully rather than just hammering away and throwing faults.

@NeilEdwards — interesting angle on EV demand, though that feels a bit upstream of what most of us can influence from a static pitch!

LazyFisher | Posts: 203 | Narrowboat

My Fogstar pulled the same stunt moored up near Foxton last winter — turns out the bilge was colder than the ambient air temp the BMS was "reading," so by the time the sensor panicked it was already game over. 🛶❄️

Wrapping the battery in a bit of closed-cell foam bought me just enough thermal mass overnight to stop it reaching cutoff — not glamorous, not Victron-approved, but it meant the kettle worked in the morning and that's basically my only metric for success.

MarineVicky | Posts: 287 | Array

This exact scenario played out for me on a January trip to the Cairngorms in my motorhome — woke up to a completely dead Victron system, frost on the inside of the windows, and a BMS that had noped out somewhere around 2am.

What saved me the following winter was wrapping the battery compartment with self-adhesive foam insulation and tucking a small 12V heating mat (thermostatically controlled, pulls almost nothing) underneath the lithiums. The BMS never sees below 5°C now even when ambient is brutal.

The bit nobody tells you — it's not just the cutoff itself that's the problem. It's that once the BMS trips, you can't even run the van heater to warm the battery back up. You're stuck in this brilliant catch-22 at stupid o'clock in the dark.