Anyone running lithium on a narrowboat with a 12V domestic bank — worth it vs AGM?

Been doing a fair bit of research after setting up a small Victron/Fogstar system in my garden office, and now I'm curious whether the same logic applies to a narrowboat setup. The usable capacity argument for lithium seems even more compelling when you're living aboard or doing longer cruises and can't always rely on shore power.

Specifically looking at a 200–300Ah 12V domestic bank. From what I've read, the main sticking points on boats (vs vans or static installs) seem to be the BMS behaviour when charging from a traditional alternator — apparently it can kill the alternator if the BMS cuts out under load? Had a Victron Orion DC-DC isolator recommended to me as the fix for that.

Also wondering how people are handling heating on the canal — I imagine most still run a diesel stove or Webasto rather than trying to do it electrically, which must take a lot of pressure off the battery bank in winter. Is that a fair assumption, or are people going full electric for heating too?

DustyHiker | 847 posts

@Macca97 the garden office logic does carry over pretty well, but narrowboats throw in a few extra wrinkles worth considering. Engine alternator charging is the big one — you'll want a proper DC-DC charger (Victron Orion is the obvious choice) rather than running lithium straight off a standard alternator, otherwise you risk cooking it when the BMS disconnects under full charge.

Also worth thinking about the weight distribution angle — lithium's significant weight saving can actually matter on a boat in ways it doesn't in a static office setup.

The other consideration is your winter mooring situation. If the boat sits unused for weeks in cold weather, lithium needs careful management around low temperatures in a way AGM doesn't particularly care about.

What's your current alternator setup, and do you do mostly continuous cruising or are there long static periods?

BatteryAlan | 1,203 posts

@Macca97 lithium on a narrowboat is basically the same maths as anywhere else — you're just doing it whilst slowly annoying fishermen. The killer advantage nobody mentions is weight: swap 200Ah AGM for 200Ah Fogstar Drift LiFePO4 and you've just removed roughly 40kg from your waterline, which your boat's hull will appreciate more than you do. BMS low-temp cutoff is worth checking before a January Midlands canal run though — AGM doesn't care if it's freezing, lithium can get a bit precious about charging below 0°C.