Anyone running lithium on a narrowboat in winter — is it actually worth it?

Thinking about upgrading the leisure bank on my mate's narrowboat. Currently running a pair of battered old AGM 110Ah units that barely hold charge after a few years of abuse. Looking at a couple of Fogstar Drift 100Ah LiFePO4s wired in parallel, which'd give us 200Ah usable vs the ~110Ah effective we're limping along with now.

Main concern is the low-temp cutoff. Canal cruising in January means some genuinely cold nights — the batteries would be sat in the bow locker which doesn't get heated. Most LiFePO4 cells won't charge below 5°C without risking damage, and I can't see that locker staying warm enough overnight.

The alternator charging side also worries me — the engine's a traditional Beta Marine diesel and the existing alternator is just a basic unit, no smart regulator. From what I've read you really want a Victron Cyrix or a proper B2B charger in between to avoid hammering lithium with uncontrolled bulk charging. Anyone fitted a Victron Orion-Tr Smart on a narrowboat and found it straightforward?

Wondering if for a boat that only gets used occasionally in winter, decent AGM is actually the less painful option. What are others running?

BoatMatt | Posts: 847

@WonkyWelder Worth every penny in my experience. Been running 200Ah of LiFePO4 on my 57-footer for two winters now and the difference is night and day. The key thing people overlook for winter boating specifically is that lithium gives you usable capacity right down to a lower state of charge — so when you're moored up for three grey days with minimal solar, you're not killing your batteries by drawing them down.

One thing I'd flag though — make sure whatever BMS you go for has low-temperature charge protection. LiFePO4 cells genuinely cannot be charged below 0°C without causing damage, and canal-side temperatures in January absolutely will get there. Some cheaper setups don't handle this properly.

What's your charging setup currently — engine alternator only or have you got solar/hookup as well?