Anyone else had grief with JK BMS cutting out at low temps this winter?

Noticed something annoying over the past few weeks with my 280Ah LiFePO4 bank in the van. Running a JK BMS (the 200A active balancer version) and it's been tripping the low-temperature protection cutoff on cold mornings — we're talking around 2–3°C inside the van. The BMS is set to cut at 5°C charge protection which I thought was sensible, but it's killing my Victron MPPT before I've even had a brew. Discharge seems fine, it's purely the charge side cutting out.

I've seen a few folk online suggesting you can dial the charge low-temp threshold down to 0°C without risking the cells, but I'm not convinced that's the right move. My cells are EVE 280Ah grade A from Docan, and from what I can find the spec sheet says charge should stay above 0°C — so technically 5°C is already a decent safety margin. Problem is in practice it's just too cautious for shoulder-season van life in the Midlands.

Has anyone fitted a self-heating solution to their battery enclosure? I've been looking at a simple 12V heat mat wired to a cheap temperature controller (the inkbird ones seem popular) to keep the bank above 8°C or so. Wondering what wattage people have found sufficient for a reasonably insulated wooden enclosure — mine is 18mm ply, roughly 600x400x300mm. Would love to know what's actually worked before I start buying bits.

Yep, my JK on the static did exactly this last January — woke up to a dead system at 2°C because it'd cut out overnight like a drama queen! 🥶

Worth checking your low temp charge cutoff threshold in the JK app — mine was set to 5°C from factory which is arguably too cautious for LiFePO4 discharge (charge protection is the important one). Knocked mine down to 0°C for discharge cutoff and haven't had grief since.

Also — if your battery's sitting exposed under the van, a cheap self-regulating heat mat wired to a thermostat sorted my mate's identical issue for about £30 all-in. Fogstar actually mentioned this in one of their guides too.

The JK app is your best friend here, half these "faults" are just overzealous factory defaults! 🔧

Same issue last winter with my setup. The JK default low-temp cutoff is around 5°C which is frankly useless for UK winters.

Worth doing two things:

1. Lower the protection threshold in the JK app — I dropped mine to 0°C with a 2°C release, which gives more usable range without being reckless with the cells
2. Add a battery heater mat — Fogstar sell decent ones, or a cheap reptile heat mat with a thermostat controller works fine

If it's in a van, insulating the battery box makes a surprising difference too. Mine went from cutting out regularly to barely triggering all winter just from 25mm foam board around the compartment.

Don't just disable low-temp protection entirely though — charging into cold LiFePO4 causes permanent damage. The threshold adjustment is the sensible middle ground.

Had this exact battle last winter. Worth knowing the JK app lets you adjust the low-temp protection threshold — I dropped mine to 0°C for discharge and kept charge cutoff at 5°C, which is the sensible split since charging cold LiFePO4 is what actually damages the cells, not discharging.

@MidlandsOffGrid if you're in a van you might also consider a small self-heating cable wrapped around the battery — mine's on a simple thermostat that kicks in around 3°C, draws minimal power and keeps everything ticking over nicely through the night. Bit of upfront faff but transformed my winter reliability completely.

Also worth checking your BMS firmware version — JK pushed an update a while back that improved the temperature sensor accuracy, as some earlier units were reading a degree or two colder than reality.

Dropped mine to 0°C like @OffGridKing suggests but also slapped a self-regulating heat mat (the 12V kind off Amazon) directly on the cells — Fogstar cells stay toasty enough now that the JK barely blinks even parked up in a Tesco car park in January.