Anyone else running lithium on a narrowboat? Struggling with my BMS tripping in cold weather

I've been living aboard my 57ft narrowboat for about three years now and finally made the jump from AGM to lithium last autumn — 200Ah of Epoch 12V LiFePO4 hooked up to a Victron SmartSolar 100/30 and a Multiplus 12/1200. Overall I'm chuffed with the decision, but I've hit a frustrating issue over winter that I can't fully get my head around.

When the temperatures dropped below around 4°C — which happened a fair bit moored up in Cheshire — my BMS kept cutting out charging mid-session. I've got low-temperature charge protection set on the battery itself, which I understand is necessary, but the Victron kit doesn't seem to "know" this has happened cleanly. I end up with the MPPT throwing fault codes and having to manually reset things on cold mornings. Not ideal when you're half asleep and just want a brew.

I've been reading about using a Victron temperature sensor and tweaking absorption settings, and also seen folk mention a relay to physically disconnect the charger before the BMS trips — but I'm not sure which approach is actually cleaner or more reliable on a boat where things get damp and vibration is a factor. Has anyone sorted this properly? What kit did you end up using and did it actually solve it long-term?

@VickyMurray the cold weather BMS cutoff is a classic LiFePO4 headache on boats — charging below around 5°C can genuinely damage the cells, so the BMS is doing its job, annoyingly.

Few things worth checking:

• Victron MPPT temperature compensation — if you've got a SmartSolar you can grab a Smart Battery Sense and it'll throttle charge current automatically based on cell temp
• Battery placement matters massively — engine bay stays warmer than a bow locker, obviously
• Where exactly are your Epoch batteries mounted? Bilge-adjacent can get brutal overnight in winter moorings

I ran Fogstar Drift cells in my garden office through last winter and even a basic self-heating mat under the battery box made a huge difference. Narrowboat engine heat might give you a similar passive solution depending on your layout.

What's the actual cutoff temp your BMS is set to?

Really feel your pain on this one @VickyMurray — went through exactly the same thing last winter on my 60ft trad.

One thing worth looking at that hasn't been mentioned yet is your Victron's temperature compensation settings. If you've got a battery temperature sensor fitted, you can set a low-temp charge disconnect in VictronConnect that works with your BMS rather than just relying on it as a last resort. Means the system backs off gracefully before the BMS has to do the hard cut.

Also worth checking where your batteries are physically sitting — under the cratch or engine bay? A bit of closed-cell foam insulation around them makes a surprising difference when you're moored up overnight with no engine running. Mine barely dips below 8°C now even in proper cold snaps.

What's your current SOC when the trips are happening?

Really useful thread this — @VickyMurray I had similar issues on my sister's cruiser last winter.

One thing nobody's mentioned yet: have a look at whether your Victron SmartSolar has the low temperature cutoff feature enabled in the settings. There's a dedicated option in VictorConnect where you can set a charge disconnect temperature threshold — if it's not configured properly it may be fighting against your BMS rather than working with it.

Also worth checking whether your battery has a self-heating function. Some of the newer Epoch units do, meaning they'll warm themselves before accepting charge. If yours doesn't, even a small 12V heat mat underneath the battery connected to a thermostat can make a real difference once temperatures drop below 5°C on the cut.

What's the installation location like — are the batteries in the engine bay or further forward?

Good thread this. One thing worth adding — have you looked at your charge current settings in the Victron app? Even if your BMS has low-temp protection, you can set a conservative absorption voltage for winter which puts less stress on the cells during cold morning starts. I've also found that running a small DC-DC charger off your engine alternator rather than pushing everything through the solar controller gives you a gentler, more controlled charge profile when it's really bitter out.

Also worth checking whether your Epoch BMS has a heating function built in — some of their newer units do, which takes a lot of the faff out of cold weather management. If not, a self-heating battery blanket timed to kick on an hour before your panels start producing can make a real difference on those February mornings. @Gibbo39's point about the trad setup rings true too.

Really good points already made here. One thing I'd add @VickyMurray — have you considered where your battery bank is physically situated on the boat? On narrowboats the bow and stern locker temperatures can drop significantly lower than midships, sometimes several degrees colder than you'd expect. If your batteries are in an exposed cratch or engine bay that's poorly insulated, you might be hitting low-temp cutoff even when the ambient inside feels fine.

A cheap wireless temperature sensor (Inkbird do decent ones) stuck directly on the battery casing rather than relying on the BMS's own reading gave me a real eye-opener when I did this on mine. Sometimes the BMS thermistor placement isn't ideal from the factory. Worth knowing your actual cell temps before throwing money at a heating solution.