What's the realistic lifespan of LiFePO4 cells in a narrowboat setup — anyone got long-term data?

Thinking about upgrading my current 200Ah AGM bank on the narrowboat to LiFePO4. The Fogstar Drift 200Ah cells keep catching my eye, mainly on price, but I'm trying to work out if the real-world cycle life matches what's on the tin. Manufacturers quote 2000–4000 cycles but that always feels like lab conditions to me.

My concern is the environment — a narrowboat isn't exactly gentle. We're talking dampness, temperature swings, vibration from the engine, and the battery box is in a mid-cabin locker that can get proper cold in winter (sub-5°C sometimes). Does that kind of environment meaningfully chew through cycle life faster than the spec sheet suggests?

Currently running a Victron SmartSolar 100/30 and a B2B charger off the Beta 43. The charging side seems sorted — it's more about whether the cells themselves will last. Has anyone had LiFePO4 on a liveaboard or continuous cruiser for 4–5 years and can share actual capacity figures rather than theoretical ones?

DriftMaster | 847 posts

@JulieAllen funnily enough the name checks out for me here! 😄

I've had a 280Ah Fogstar Drift bank running on my narrowboat since early 2022 — so getting on for three years of fairly heavy use, continuous liveaboard, running through winter on a 40A alternator with a Victron alternator protection relay.

Cells are still sitting at 99% capacity according to my BMV-712. LiFePO4 chemistry is genuinely different to other lithium types — the flat discharge curve isn't just a convenience feature, it's part of why the cells degrade so slowly. Manufacturers quote 2,000-4,000 cycles to 80% capacity, and real-world reports from the narrowboat community seem to be tracking that fairly honestly.

The bigger risk on boats isn't cycle degradation honestly — it's poor BMS configuration or dodgy alternator setups cooking them. Get those right and you should realistically be looking at 10+ years.

DustyNomad | 234 posts

Not a narrowboat setup but my garden office runs a 200Ah Fogstar Drift bank — going on 18 months now with no degradation I can measure via the Victron BMV-712.

The cycle life question really hinges on your narrowboat usage pattern. If you're doing shallow 20-30% DoD cycles most days (typical liveaboard), you could realistically see 4,000-6,000+ cycles — that's potentially 10-15 years. Run them hard to 80% DoD regularly and you'll sit closer to the lower end of the manufacturer's 2,000-cycle figure.

Worth factoring in: LiFePO4 chemistry is genuinely more stable than other lithium types in the thermal stress conditions a boat hull creates. Boats get warm.

The bigger risk to longevity is usually the BMS configuration rather than the cells themselves. What's your planned BMS setup?