Anyone else had their BMS trip mid-journey on a narrowboat? Nearly lost steerage 😅

So there I was, chugging up the Grand Union last August, kettle on, inverter humming, living my best life — when the whole 12V system just died. Turns out my 200Ah Fogstar Drift LiFePO4 decided that precise moment was the ideal time for the BMS to throw a low-voltage protection trip. Down to 2.8V per cell apparently, because I'd been running the diesel heater blower all night without enough solar input to keep up. Rookie error, I know.

The bit that proper annoyed me was the BMS latching off with no warning. No alarm, no gradual shutdown, just — gone. I've since added a Victron BMV-712 to get some actual data and low-voltage alerts, which has been transformative. But I'm still unsure whether my BMS settings are dialled in correctly. Currently running low-voltage disconnect at 44V (12S pack, so roughly 3.0V/cell) and reconnect at 50V (3.45V/cell). Feels conservative but I'm a coward now.

What are you lot running for LVD and reconnect thresholds on your LiFePO4 setups? Particularly curious whether anyone on a boat has different priorities to, say, a motorhome build — I imagine losing your bow thruster is a different kind of bad day to losing your 240V coffee maker.

EllaDavies | ⚡ 847 posts | Midlands

Oh no @BoxerCamper, that sinking feeling (hopefully not literally!) when the instruments go dark mid-canal is genuinely alarming.

What was your cell voltage sitting at when it tripped? I'd wager either low voltage cutoff from running the kettle with depleted cells, or possibly a temperature protection trigger — August can be brutal in an enclosed battery compartment with no airflow.

Worth having a look at your BMS logs if it supports Bluetooth monitoring. The Fogstar Drift is decent kit but narrowboat installations are their own beast — engine vibration, inconsistent alternator charging, loads cutting in suddenly.

I've started carrying a small 12V jump pack specifically to reset my BMS in emergencies rather than hunting for the manual override. Saved me a very embarrassing situation on the Llangollen last spring! 🙈

OakSoul | ⚡ 23 posts | Array

Different context but same panic — mine tripped while I was mid-charge on my EV setup at home, killed the whole array. Took me ages to figure out it was a voltage spike from the charger that the BMS read as an overvoltage event.

Couple of questions for @BoxerCamper:

• What was your SOC when it happened?
• Were you running the kettle and the inverter simultaneously, or just one?
• Any idea what your peak draw was at the point of shutdown?

I've been reading that some Fogstar Drift units can be a bit sensitive to sudden high-current demands — wondering if it's an overcurrent trip rather than a low-voltage cutoff? Has anyone used a Victron SmartShunt alongside these to get better real-time data on what actually triggered the BMS event?

Cleggy51 | ⚡ 312 posts | Yorkshire

Had almost the exact same on the Llangollen two summers back, @BoxerCamper — killed the helm electrics right as I was approaching a lock. Not ideal! 😬

The culprit for me was running the kettle AND the inverter charger simultaneously while the bank was already low from overnight. BMS saw a brief voltage sag and noped right out.

What sorted it was adding a small dedicated 12V lead-acid buffer just for the boat's critical systems — steerage, bilge pump, nav lights — completely isolated from the leisure bank. LiFePO4 is brilliant but that hard cutoff is absolutely unforgiving compared to old AGM which at least gives you a bit of warning as it sags.

Worth checking what your low-voltage cutoff threshold is set to as well — some Fogstar units ship quite conservative from the factory.

Neil1978 | ⚡ 1,204 posts | East Midlands

Classic BMS protection doing its job at the worst possible moment! @BoxerCamper worth checking whether it was an undervoltage trip or overcurrent — kettles are notorious for pulling a massive spike through the inverter, especially if your cable run to the inverter is on the longer side and has any resistance built up over time.

After a similar incident I fitted a small 12V bilge pump and nav lights circuit on a completely separate fused feed before the BMS output, so at least the safety-critical stuff stays live regardless. Obviously that's only really viable if your BMS has decent short-circuit protection elsewhere.

What firmware/settings are you running on the Fogstar? Some of the earlier units shipped with quite conservative overcurrent thresholds that you can adjust if you've got the cable and the Overkill Solar app. 🔧

RetiredChef2 | ⚡ 47 posts | Array

This is my nightmare scenario — I've got a 200Ah LiFePO4 bank on my 32ft narrowboat and I'm always slightly anxious about exactly this happening.

Can I ask @BoxerCamper — was it an over-current trip or a low-voltage cutoff? I'm trying to understand whether adding a small lead-acid buffer for the helm electronics would be worth the hassle as a fallback.

Also wondering if anyone's running a secondary dedicated 12V circuit just for navigation/steerage that bypasses the main bank entirely? Seems like the sensible approach for anything safety-critical, but I haven't found a clean way to wire it without it getting complicated fast.

My Victron BMV-712 gives me early warning but that's no use if the BMS just cuts without warning mid-load spike.

VanSue | ⚡ 847 posts | Array

Been there — not on the cut but had my Victron SmartShunt log a similar BMS trip on my garden office setup and the cause surprised me. Turned out a loose negative busbar connection was spiking the internal resistance readings and the BMS was seeing a phantom over-current event. Nothing actually wrong with the cells themselves.

@RetiredChef2 worth pulling your BMS logs if it supports Bluetooth — Fogstar Drift's app will show you exactly what triggered the disconnect. High-rate discharge + a marginal connection = BMS goes nuclear.

For a narrowboat I'd seriously look at adding a dedicated low-voltage pre-alarm wired to something you will notice before the full trip cuts in. Gives you time to shed loads rather than losing steerage with zero warning.

TrevorLamb | ⚡ 312 posts | Shropshire Union Canal

Worth checking whether it was an over-discharge trip or a temperature cutoff @BoxerCamper — LiFePO4 cells hate the cold and if you were out early morning in August with overnight temperatures dropping, the BMS may well have throttled things before you'd even noticed the SOC dropping. The fix I swear by is setting a low-voltage warning alarm on your Victron or SmartShunt well before the BMS protection threshold kicks in — gives you enough time to shed loads deliberately rather than having everything cut out at once. Steerage is non-negotiable on a narrowboat, so it's worth segregating your 12V ignition/engine circuits entirely from the domestic bank if possible.