Anyone else running lithium on a narrowboat — how are you handling the BSS inspection?

I've just finished converting my 57ft trad stern narrowboat from a pair of 110Ah AGM batteries to a 200Ah LiFePO4 setup (Fogstar Drift if anyone's curious). The install itself went pretty smoothly — 40A DC-DC charger off the alternator, a 30A MPPT from two 175W panels on the roof, and a Victron BMV-712 keeping an eye on everything. Really pleased with how it's come together.

The bit that's nagging at me now is the Boat Safety Scheme examination coming up in about eight months. From what I can gather, the BSS assessors are still getting their heads round lithium installs — particularly around ventilation requirements and whether a BMS with low-temp cutoff satisfies their concerns about charging in cold conditions. My BMS does have that cutoff built in, but I'm not sure whether the examiner will want to see documentation for it or just take my word for it.

Has anyone here actually been through a BSS inspection with a lithium setup on a canal boat? Did your examiner flag anything unexpected, or did it go through without a hitch? I'd love to know what paperwork or evidence people found useful to have on hand.

NorfolkSolar | 847 posts | ⚡ Solar & Storage Enthusiast

@WattRoger great choice going with Fogstar Drift — solid kit.

The BSS side is worth taking seriously though. Inspectors are increasingly clued-up on lithium now, and the main sticking points I've seen raised are:

• Isolation — your BMS disconnect needs to be accessible and the examiner may want to understand how it behaves under fault conditions
• Labelling — lithium-specific hazard labels on the battery compartment
• Ventilation — LiFePO4 is far safer than other chemistries but some inspectors still want to see provision for it

My honest advice: contact your examiner before the inspection and walk them through the setup. Most appreciate the transparency and it avoids awkward surprises on the day.

Which marina are you based at? Experiences can vary quite a bit depending on who's doing your exam.

FZO_Marine | 312 posts | ⚓ Liveaboard & Off-Grid

@WattRoger good timing on this thread — BSS and lithium is still a bit of a grey area that catches people out. The key thing examiners are focusing on is whether your battery isolation is adequate and whether the install poses any fire or gas risk. LiFePO4 is actually quite favourable on that front compared to lead-acid since there's no hydrogen off-gassing, so ventilation requirements are less stringent.

That said, make sure your cabling is properly fused close to the battery terminals and that your BMS disconnect can't leave loads unswitched in a fault condition. Some examiners are also starting to ask about thermal runaway mitigation, so having your batteries in a ventilated enclosure helps even if it's not strictly mandatory yet.

Do you have a shore power setup involved as well? That changes things slightly.

DodgyHermit | 203 posts | 🌞 Solar & Shepherds Huts

Not on a narrowboat myself — I run a similar Fogstar Drift setup in a shepherd's hut — but I've been following the BSS lithium situation closely because the inspection framework genuinely hasn't kept pace with LiFePO4 adoption.

Main thing I'd flag: make sure your BMS disconnect behaviour is documented. Inspectors increasingly want to see that a fault condition won't leave you with an uncontrolled disconnect mid-cruise (prop drive aside, but you know what I mean — DC loads dropping suddenly).

Victron's DVCC setup plays nicely here if you're using a Cerbo, as it gives you a paper trail of sorts.

Worth contacting your BSS examiner before the inspection date rather than turning up and hoping. Some are far more clued-up on lithium than others — lottery really.

BatteryGill | 521 posts | 🔋 Cabin & Emergency Backup

My BSS examiner took one look at my Victron BMS documentation and suddenly became very interested in the ceiling — turns out "I've never actually failed a lithium install" is their way of saying "I have no idea what I'm looking at either." 📋

Seriously though @WattRoger, the magic words are cell-level overcharge/over-discharge protection and thermal runaway mitigation — get those phrases into any paperwork and most examiners will nod along like they planned the whole thing themselves.