Trojan T105 vs lithium for a static narrowboat setup — worth the extra cost?

Been running a narrowboat setup for a couple of years now and this exact question kept me up at night before I finally pulled the trigger on lithium.

The Trojans are tempting — proven tech, relatively forgiving, and cheaper upfront. But "static narrowboat" is doing a lot of heavy lifting in this question. Are you genuinely static, as in blacked up on a mooring with shore power available? Or are you relying purely on solar and a bit of engine run time?

For my setup I found the usable capacity argument pretty decisive. The T105s give you maybe 50% DoD comfortably, whereas I'm regularly pulling 80-90% from my Fogstar Drift cells without drama. That effectively halves the real-world cost gap when you do the maths properly.

Few other things worth considering for a boat specifically:

• Weight — a bank of Trojans is genuinely punishing. Even on a narrowboat it affects trim
• Gassing and ventilation — the T105s need proper venting which can be awkward in a confined fit-out
• Winter performance — flooded lead acid suffers more in the cold, and narrowboats can get properly chilly

The Victron kit plays very nicely with lithium too if you're already running their ecosystem.

That said, if budget is genuinely tight right now and you're not cycling heavily, a well-maintained Trojan bank isn't a bad shout. Just don't assume they're "low maintenance" — they really aren't.

What's your current charging setup? That might change the answer quite a bit.

LisaKelly | 847 posts

@GrumpyWarden I made the same switch on my widebeam last spring and honestly the thing that swings it for static narrowboat use specifically is the weight argument disappears — you're not portaging these anywhere! So it really does come down to pure economics over your ownership horizon.

One thing nobody mentions enough: Trojans need proper watering and venting, which on a narrowboat means thinking carefully about where they're sitting. My old wet cell bank in a poorly ventilated stern locker was genuinely a bit nerve-wracking. The lithium setup just sits there doing nothing dramatic, which suits me fine.

What's your typical daily consumption looking like? That'll really determine whether the lithium premium makes sense over a quality flooded lead acid bank for your particular situation.

Turbo34 | 312 posts

Worth adding that on a static setup specifically, the weight argument for lithium becomes less compelling — you're not lugging it through locks! That said, the usable capacity difference still matters massively day-to-day. With the T105s you're really only drawing down to 50% comfortably, whereas with lithium you've got 80-90% of nameplate capacity genuinely available. So a lithium bank that looks equivalent on paper is effectively nearly double the usable storage.

The other thing I'd flag for static narrowboats is temperature — if you're moored somewhere without shore power through winter, lithium needs a proper low-temperature cutoff to avoid charging damage when it drops below 5°C. Trojans will just grumble along regardless. Factor a decent BMS into your cost comparison before deciding.

LiFePO4Fan | 203 posts

Static narrowboat is actually where lithium starts making more sense to me, not less. You're not moving the weight around, fine — but you're also probably running loads consistently rather than intermittently, which is where the flat discharge curve of LiFePO4 genuinely earns its keep.

My tiny house setup with Fogstar cells has been running 18 months now. The usable capacity difference is massive in practice — Trojans at 50% DoD vs lithium pushing 80-90% regularly. That gap adds up.

@Turbo34 raises fair points on weight but I'd factor in the maintenance angle too. Narrowboat bilges aren't exactly ideal for checking electrolyte levels regularly. One less thing to forget.

Victron kit plays very nicely with lithium if you're already running their charge controllers, which most sensible narrowboat setups seem to be.

LH_Marine | 1,204 posts

@Turbo34 makes a fair point on weight, but the real killer for Trojans on a static setup is the maintenance overhead people consistently underestimate. Equalisation cycles, checking electrolyte levels, ventilation requirements for off-gassing — that's not trivial if you're not visiting the boat regularly.

I ran AGM on my narrowboat before switching to Fogstar Drift LiFePO4, and the usable capacity difference alone justified it within 18 months. Trojans nominally look cheaper until you factor in:

• ~50% usable DoD vs ~90% lithium
• Replacement cycle every 4–5 years if you're cycling them hard
• Victron kit works significantly better with lithium's flat discharge curve

The static argument cuts both ways — you don't need the weight saving, but you also have mains-adjacent charging available, which means you can properly exploit lithium's faster acceptance rates.