Anyone else had their BMS cut out in cold weather? Trying to figure out if it's the cells or the settings

Been having a frustrating few weeks with my 280Ah LiFePO4 pack (four EVE cells in series, 12V setup). Running a Daly 100A BMS and it's been tripping off in the mornings when temps drop below about 5°C in my shed. Voltage looks fine on the cells individually — sitting around 3.28V each — but the BMS just disconnects and I have to manually reset it. No obvious error code showing on the Daly app either, which isn't exactly helpful.

I'm wondering whether the low-temp cutoff is set too conservatively out of the box. From what I've read, LiFePO4 can still discharge safely down to around 0°C, and my cells aren't actually freezing — I've got a thermometer in there and the coldest I've seen is 3°C. Charging is a different matter and I've already got that locked out below 5°C, which seems sensible. But discharge cutoff at these temps feels like it's causing me grief for no good reason.

Has anyone played around with the low-temp discharge settings on a Daly? I've got the PC software but I'm a bit wary of just changing values without knowing what's reasonable. Would love to know what temperatures others are running discharge down to, especially if you're in an unheated outbuilding or a van that sits outside overnight.

FEE_Solar | 847 posts

@MuddyGrafter Almost certainly your BMS low-temperature cutoff doing exactly what it's supposed to do, to be fair. LiFePO4 cells really don't like being charged below 5°C — you can cause lithium plating on the anode which permanently damages capacity.

Check your Daly app or settings — there'll be a separate charge low-temp protection threshold, usually factory-set somewhere around 5°C. You can lower it slightly but I'd honestly leave it where it is.

The practical fix is insulating the battery box rather than fighting the BMS. Even a simple foam-lined wooden enclosure makes a surprising difference. Some folk stick a small self-regulating heat mat underneath, wired to cut out once the pack reaches 10°C.

What's your charging source — solar, mains, alternator? That might affect the best solution for your setup.

@MuddyGrafter this is almost certainly your low-temperature charge protection triggering, not a fault as such. LiFePO4 cells can be permanently damaged by charging below 0°C, so the Daly is doing its job.

The 5°C cutoff is actually quite conservative — EVE's own datasheet specifies 0°C as the lower charge limit, so your BMS threshold might be set a touch high, or there's a sensor placement issue (sensor reading colder than actual cell temperature).

Worth checking:

• Where is the temperature sensor physically sitting? Against the cell surface or floating in air?
• Is it discharge cutoff or charge cutoff tripping? The Daly app should tell you which protection activated.

On my cabin build I moved the sensor to sit directly under a neoprene wrap against the cell body — stopped nuisance trips immediately. Insulating the battery compartment made a bigger long-term difference though.

OakSeeker | 23 posts

Had almost identical on my boat last winter — woke up to a dead system at 0600 with the heating off. Miserable.

One thing worth checking beyond the BMS settings: are your cells actually at 5°C or is the sensor reading that? On my setup the Daly sensor was zip-tied to the outside of the case and reading ambient. Actual cell temp was a couple of degrees warmer due to the insulation around the pack.

Worth wrapping the battery box in some closed-cell foam if you haven't already — made a noticeable difference for me over winter. Doesn't take much to keep cells above the cutoff threshold overnight when they're not being heavily discharged.

What's your low-temp charge cutoff set to in the Daly app? There's a few different parameters in there that can catch people out.

ColBurns63 | 312 posts

@MuddyGrafter Worth checking whether it's cutting out on charge or discharge as well — they're separate protections on the Daly and behave differently. If it's only killing charge (solar/alternator input) but still allowing loads to run, that's actually the BMS doing its job perfectly. If it's cutting discharge too, you might have the low-temp discharge threshold set too conservatively.

The Daly PC software lets you adjust both thresholds independently. Default low-temp charge cutoff is usually around 5°C which matches what you're describing exactly. Some folk drop it to 0°C, though personally I wouldn't go below that with EVE cells.

A cheap self-adhesive heat mat on the battery with a temperature controller set to kick in around 5°C sorted mine completely — draws minimal power overnight and keeps everything ticking along through winter.