Anyone else had their BMS cut out mid-journey with a Fogstar Drift 100Ah?

Picked up a Fogstar Drift 100Ah LiFePO4 last spring for the motorhome, wired it into a Victron SmartSolar 100/20 setup with a 200W Renogy panel on the roof. All ran beautifully for about four months — genuinely impressed with it.

Then last week, somewhere on the A9 heading up to Inverness, the whole 12V system just died. No warning, no low voltage alarm, nothing. Pulled over, checked the Victron app — battery had been sitting at a healthy 13.1V not twenty minutes before. Turned out the internal BMS had tripped on what I can only assume was a temperature issue; it was a bitter morning and the battery was tucked in the underfloor locker with zero insulation around it.

Reset it manually and it came back fine, but now I'm second-guessing the whole setup. Has anyone else seen cold-triggered BMS cutouts with the Drift range specifically? I'm wondering whether wrapping it in some closed-cell foam would be enough, or whether I need to look at a proper heating pad solution for Scottish winters. What temperatures are people seeing before the low-temp protection kicks in?

@WendyFisher61 oh this is timely — I've been half-convinced my Fogstar Drift is doing something similar in my garden office setup, though mine cuts briefly then recovers rather than staying out.

Can I ask what your ambient temps were like when it happened? I've noticed mine gets a bit twitchy in the colder mornings lately and I'm wondering if the low-temp protection is triggering prematurely.

Also — was your Victron showing any fault codes beforehand, or did it just drop without warning? Mine's connected via the VE.Direct so I can pull history but honestly I haven't dug into it properly yet.

Four months of solid performance then suddenly this is annoying isn't it — you start trusting the thing and then it lets you down at the worst moment. Did Fogstar's support respond when you contacted them?

@WendyFisher61 worth pulling the Victron app history first — the SmartSolar logs will show exactly what the battery voltage was doing before the cutout. BMS trips on LiFePO4 are almost always either over-voltage (charger absorption set too high), under-voltage (load pulled it too low), or over-temperature.

The Drift's BMS trips at 3.65V/cell upper limit — if your SmartSolar absorption is set above 14.6V you're potentially tickling that threshold repeatedly, which degrades the BMS response over time.

In my shepherd's hut setup I run absorption at 14.2V with a float of 13.5V — conservative, but I've had zero BMS events across 18 months.

Also check your cabling — undersized wire creates enough voltage drop under load to confuse the BMS into thinking there's a cell imbalance. What gauge are you running between battery and load bus?

@WendyFisher61 Had something similar with mine last summer — turned out my cable run was slightly undersized for the load I was pulling, so voltage drop under heavy draw was tripping the BMS before the Victron even registered a problem. Worth checking your cable gauge and connection resistance end-to-end before assuming it's a battery fault. Also, what loads are you running when it cuts out? If it's consistently happening with something like a kettle or compressor fridge kicking in, you might be hitting the BMS overcurrent threshold rather than a low voltage event. @JYT_Solar's point about the Victron logs is solid — but also check if Fogstar have updated their BMS firmware recently, as I recall there was some chatter about early Drift units being a touch oversensitive on the protection settings.

@WendyFisher61 just wanted to add — worth checking your battery terminal connections before going too deep into the diagnostics. I had a BMS cutout on a different LiFePO4 that turned out to be a slightly loose negative terminal causing intermittent resistance under load. The BMS was reading a voltage spike and protecting itself perfectly correctly, it just looked like a random fault.

Also, what's your load profile when it cuts out? If it's consistently happening under higher draw (inverter kicking in, kettle, that sort of thing) that points somewhere different than if it's random at low loads. The Drift is generally a solid battery so I'd be surprised if it's a duff unit — more likely something upstream causing grief. Keep us posted once you've had a look!

My Fogstar Drift did exactly this on the Thames near Twickenham — turned out the BMS was doing its job perfectly and my inverter was the gobby culprit pulling brief spikes that looked like a short to the protection circuit. 🔌