Anyone else had BMS cut-out issues with Fogstar Drift cells in cold weather?

Running a 200Ah 12V lithium setup in my static caravan in Scotland — four Fogstar Drift 50Ah cells in parallel, with a Daly 100A BMS. Been solid all summer but now we're getting nights dropping to 2–4°C inside the van and I'm seeing the BMS trip out randomly, usually around 3–4am.

Voltages look fine on the Victron BMV-712 — sitting at 12.8V when it cuts, so it's not an undervoltage fault. My suspicion is the Daly is triggering on over-discharge current protection, possibly because the internal resistance climbs in the cold and confuses the readings. Has anyone else seen this with LiFePO4 cells at low temps, or is the Daly just a bit rubbish at temperature compensation?

Wondering whether it's worth swapping the Daly out for something like a JK BMS — I've heard they handle temperature fluctuations better and have more granular settings. Or is there a simpler fix, like wrapping the cells in insulation to keep the temp more stable overnight? What are people actually doing in real cold-weather installs?

BoxerLife | Posts: 847

@LisaStewart71 Classic cold weather BMS behaviour — the Daly units are particularly twitchy around that 2–4°C range. Worth checking your low temperature disconnect setting in the Daly app if you haven't already; mine was factory set at 5°C which caused identical grief last winter.

The Drift cells themselves handle cold reasonably well but you really don't want to be charging them below 0°C regardless. If the BMS is cutting out during discharge rather than charge cycles though, that's likely just the temperature threshold being overly cautious.

Cheap fix worth trying first — a small self-regulating heat mat underneath the battery bank, controlled by a simple thermostat set to kick in around 5°C. Transformed my setup in an uninsulated outbuilding. Whole lot costs about £20–30.

What's your charging source — solar, hookup, or both?

IslandExplorer | Posts: 312

@LisaStewart71 Worth checking whether your Daly is cutting on discharge or charge protection — they're different issues. At 2–4°C you're likely still fine for discharge, but if your charger is pushing anything above trickle into cold cells the BMS will (correctly) trip on low-temp charge protection.

Fogstar Drift cells are solid but they do need that protection respected — charging lithium below ~5°C causes lithium plating, which is permanent damage.

Practical fix: add a cheap temperature sensor on the battery bank and either:

• Use a Victron charger with low-temp cutoff built in
• Or wire a simple thermostat to interrupt charge input below 8°C

I run a similar setup in my garden office and had identical grief last January until I sorted the charge-side temperature cutoff properly. Discharge carried on fine throughout.

MeadowDweller | Posts: 1,203

@LisaStewart71 The Fogstar Drift cells are rated down to 0°C for charging — below that the BMS should cut charge protection, which is correct behaviour rather than a fault. Discharging is generally fine to around -20°C.

Worth adding a simple temperature probe to confirm what's actually triggering the cutout, as @IslandExplorer suggests distinguishing charge vs discharge events is the right diagnostic step.

On my narrowboat I solved a similar issue by wrapping the battery bank in 25mm foam insulation and adding a small 10W heat mat on a thermostat, set to kick in at 5°C. Keeps the cells above the charge threshold overnight without burning much power.

A Victron Smart BMS with the temperature sensor option gives you far better visibility and configurable thresholds than the Daly — worth considering if you're already thinking about upgrading the BMS.

Trigger63 | Posts: 2,156

@LisaStewart71 Good point from @MeadowDweller about the 0°C charge limit — worth adding that even approaching that threshold the Daly gets nervous and can trip preemptively, sometimes as high as 3–4°C depending on how the thermistor is positioned. If yours is mounted on the BMS board rather than directly on the cells, there's likely a temperature lag and the actual cell surface is colder than it's reporting. Try taping the sensor directly onto the cell casing if you haven't already. Also, a small amount of insulation around the battery bank makes a surprising difference in a static — even basic camping foam matting can keep temps a couple of degrees higher overnight without much effort or cost.

BordersSolar | Posts: 2,156

@LisaStewart71 I run a similar setup in the Borders so I know exactly what you're dealing with! One thing nobody's mentioned yet — have you checked whether your BMS has low-temperature charge protection enabled in the settings? On the Daly you can connect via Bluetooth app and adjust the temperature cutoff thresholds. Mine was factory-set overly cautiously and kept tripping at 5°C rather than 0°C.

Also worth considering a simple insulated battery enclosure — even basic camping foam around the battery box makes a surprising difference overnight. Some folk add a small thermostatically controlled heat mat underneath, though obviously that draws a bit of power.

As @MeadowDweller says, 0°C is the hard limit for charging, so protecting against that is sensible anyway. Scottish winters will only get tougher from here!

PanelRob | Posts: 847

Scottish winters eating your BMS for breakfast — classic. Worth knowing the Daly's low-temp cutoff threshold is configurable in the PC software, so you might already be tripping a programmable limit rather than hitting the cell's actual chemistry wall. Grabbed a cheap self-regulating heating pad off Amazon (the kind used for reptile tanks, ironically) and stuck it under my bank in the van — keeps things above 5°C overnight for pennies. Also worth checking whether your charger has a low-temp charge inhibit setting separately — my Victron SmartSolar handles this natively via the battery temperature sensor dongle, stops the whole sorry saga before the BMS even gets involved.

SomersetCamper | Posts: 412

@LisaStewart71 One thing worth checking that I haven't seen mentioned — are your cells actually at 2–4°C or are they warmer inside the caravan? Lithium cells self-heat slightly under load, and if they're in an insulated battery box inside rather than in an external locker, they may be staying above the BMS cutoff threshold even on cold nights. Mine sit in a foam-lined box under the seating and rarely drop as low as ambient. Might save you some hassle before going down the heating element route.