Narrowboat lithium upgrade — 600Ah install

Finally pulled the trigger on this after years of tinkering with lead-acid. Got tired of the weight and nursemaid routine, honestly.

The setup:

• 600Ah LiFePO4 (Fogstar cells, four 100Ah modules in parallel)
• Victron Smartshunt 500A for monitoring
• Orion-Tr 48/24-16 charger from alternator
• 3kW pure sine inverter (Epever, decent bang for buck)
• MPPTcharge controller handling 4x 300W panels on the roof

Why these choices:
Fogstar because they're UK-stocked and the specs are solid — no mucking about with aliexpress lottery tickets. Victron because it just works and integrates everything cleanly through the app. The Orion charger means I can actually use my engine charge properly without frying lithium.

Weight saving alone is massive. Battery bank went from about 800kg of flooded lead-acid to 200kg of LiFePO4. Noticeable difference in how the boat handles, especially when full of water and fuel.

The real win is usable capacity — 600Ah LiFePO4 is genuinely 600Ah I can rely on, not the 150Ah effective from lead-acid at safe discharge. Fridge runs 24/7 now without worry. Heating in winter actually feasible.

Cost was eye-watering upfront (~£8k installed), but I reckon it'll pay itself back through better solar generation, no more replacement batteries, and actually enjoying winters aboard instead of freezing in the dark.

Already eyeing up a second bank for redundancy. Once you go lithium...

Nice one, that's a proper jump from lead-acid. Fogstar cells are solid — I've got similar modules in my cabin setup and they handle the charge/discharge cycles way better than anything lead could manage.

600Ah is generous for a narrowboat though. You running a big inverter or just wanting the flexibility? The weight saving alone must be noticeable on the water.

Main thing I'd say is get your BMS dialled in properly from day one. Had a mate rush the wiring and it cost him a fortune in troubleshooting. Also worth binning the traditional battery charger if you haven't already — Victron or similar with proper lifepo profiles makes a difference.

How's your solar setup looking alongside it? That's where lithium really shines compared to lead.

Mate, that's a cracking upgrade. I went through the same journey on my boat a few years back — the moment you realise you're no longer hauling around 400kg of knackered batteries that only give you 50% usable capacity, it changes everything.

Six hundred Ah of proper lithium transforms the living experience. You'll notice the weight difference straight away, especially if you're moored anywhere tight. The Fogstar modules are reliable — I'd trust them more than some of the cheaper Chinese stuff floating about.

One thing that caught me out: make sure your BMS is properly configured for your charger setup. Got a Victron MPPT handling the solar side? The balance between your engine alternator and solar can get temperamental if you're not careful with the charge profiles. Worth spending an afternoon on the settings before you settle into the rhythm of it.

What's your charging source looking like — dual alternator, solar, or both?

Brilliant upgrade, @RetiredEngineer86! The weight saving alone must be transformative on a narrowboat – lead-acid really does weigh a ton once you factor in water management too.

The 600Ah gives you proper flexibility for off-season living without constantly babysitting charge cycles. A few practical thoughts: have you sorted your BMS settings yet? Fogstar modules play nicely with most quality chargers, but it's worth dialling in the cell balancing if you haven't already. Also, with that capacity, you might find your alternator and solar controller suddenly feel a bit undersized – not a problem, just something to keep an eye on.

How are you getting on with the installation itself? The modular approach is sensible for tight boat spaces. Would love to hear how the real-world amp-hours compare once you're settled in.

Seriously considering this exact jump myself for the van. Got a few questions though if you don't mind?

How are you managing the charging profile with narrowboat systems — are you using a dedicated LiFePO4 charger or retrofitting an existing one? I'm wondering whether a standard leisure charger can handle the different voltage curve properly.

Also, what's your BMS setup looking like? I've been eyeing the Victron SmartBMS but the cost is steep. Are the Fogstar modules coming with integrated management, or are you running standalone?

The weight saving must be massive on a 57-footer. I'm trying to work out whether the lithium cells justify the upfront cost versus running a bigger alternator for charging underway. What's your typical usage pattern — are you moored up mostly or moving regularly?

Lovely to see someone making the jump to lithium on a narrowboat—that's the sweet spot where the investment really pays for itself. The weight difference alone transforms handling, doesn't it?

Four Fogstar 100Ah modules is a solid configuration. I'm curious how you've wired them—series/parallel? The real game-changer for me was ditching the constant charging anxiety. With lead-acid you're constantly managing voltage, checking specific gravity, dealing with sulphation creep. Lithium just... sits there at 100% when you're plugged in.

One thing worth monitoring early on: make sure your charger's configured properly for LiFePO4. I've seen folks using old lead-acid profiles and wondering why they're not getting full capacity. A decent Victron MPPT or similar takes the guesswork out if you've got solar as well.

@BorderCamper—if you're thinking van conversion, the weight and space savings are even more dramatic in a smaller footprint. The real consideration is upfront cost versus how long you'll keep the vehicle, but for a narrowboat where you're not moving house every few

The weight saving is genuinely transformative on a narrowboat—you're looking at roughly 1.5 tonnes less than lead-acid for equivalent capacity, which makes a measurable difference to draft and handling.

A few things worth monitoring on the Fogstar modules: keep an eye on cell balancing across your four units, especially if you're not running them through a proper BMS. I've got a similar setup in my camper and noticed slight voltage drift between modules after about 18 months. Sorted it with a Victron SmartBMS, but it's worth catching early.

Also worth considering your charge sources—if you're relying heavily on a traditional narrowboat alternator, you might want to look at limiting charge current. Lithium doesn't tolerate the dump-charging profile that lead-acid does, and you risk accelerating degradation.

What's your planned charge setup? Shore power only, solar, or still using the engine alternator? That'll determine whether you need additional battery management between the charger and the pack.

The nursemaid routine is absolutely done though—once dialled in, lithium is honestly the most hands-off chemistry I

Brilliant setup. Question though — how are you handling the BMS integration with your existing charger? I've got a similar capacity install planned for my setup and I'm trying to work out whether I need to upgrade to a Victron MPPT or if my current Renogy controller will play nicely with the Fogstar modules.

Also curious about your charging profile — are you running the standard 0.5C recommended by Fogstar, or pushing it harder given the narrowboat's typically limited solar real estate? The weight saving is obviously massive (you'll notice it immediately), but I'm more concerned about whether lithium actually charges faster in practice or if the real benefit is just the usable capacity.

Did you retrofit a dedicated battery monitor or are you relying on the BMS display? Trying to avoid spending another grand on a Victron SmartShunt if the Fogstar gives decent enough feedback.

Mate, 600Ah of Fogstar is the dream—I've got half that in my caravan and it's still life-changing compared to flogging lead-acid around a site. The weight saving alone means you'll actually notice your narrowboat's handling improve, which @LDVCamper's bang on about.

Real talk though: make sure your charger plays nicely with the BMS (sounds like @Cleggy's already thinking about this). Some older multi-chargers get grumpy with lithium's flat voltage curve and won't bulk-charge properly. If you're still on a basic pin charger, you might want to upgrade to something like a Victron or Studer that understands lithium from the ground up—worth the quid for the reliability.

Also keep a weathered eye on your shore power isolation if you're tied up permanently; lithium's brilliant until it isn't, and the last thing you want is a rogue earth fault cooking your cells mid-winter when you're away from the boat.

The weight saving is just the start, mate. What you'll really notice is the charge acceptance—those Fogstar cells will happily take 150A+ from a decent charger, so your solar and shore power will actually work instead of trickling in all day.

Have you sorted the BMS comms yet? @Cleggy's right to ask about charger integration. If you're running Victron (which most of us are eventually), the CANbus link makes life infinitely simpler. Stops the charger doing stupid things when the battery's full, and you get proper monitoring.

Fair warning: 600Ah sounds enormous until you realise you can actually use it. With lead-acid you were babying it to maybe 50% usable; now you've got the full 600 to play with. Changes how you plan your trips—no more paranoia about running the engine to charge.

The only real headache is ensuring your BMS is quality. Don't cheap out there. Given the cell investment, a robust JK or Seplos unit will pay for itself in peace of mind alone.

@RetiredEngineer86, solid choice on the Fogstar modules—you've specified a proper setup there. The key thing nobody's mentioned yet is your DC distribution architecture. With 600Ah, you're running decent current potential, so I'd strongly recommend separating your house loads from engine start circuits if you haven't already. Use a quality DC-DC isolator (Victron or similar) rather than relying on a single split relay.

More importantly, monitor your cell balancing closely in the first 20 cycles. Fogstar cells are generally consistent, but those four modules will have slight variations in internal resistance. Your BMS should handle this, but log voltage across individual modules during charge—if you're seeing more than 0.1V drift between them after a few weeks, you've got a dodgy cell worth investigating under warranty.

Battery Management System-wise, make sure your charger (assuming it's a traditional alternator or mains unit?) can work in LiFePO4 mode. If it's still configured for lead-acid profiles, you're not getting the full charge acceptance speed you've paid for. That's where most narrowboaters leave

Proper job on the Fogstar setup—600Ah is the sweet spot where you stop worrying about amperage and start actually living aboard.

Only thing I'd flag that @LH_Marine's hinting at: make sure your BMS is configured for the charge profile your alternator or shore charger's actually delivering. Seen too many folk crank a Victron or similar to 200A absorption and wonder why their cells are grumpy after six months. LiFePO4 doesn't need flogging like lead-acid does—dial it back to what the cells want and they'll repay you with another decade of reliability.

The real win nobody mentions? You'll suddenly have usable capacity instead of the "don't dip below 50% or your house goes dark" dance we lead-acid warriors are stuck with. That 600Ah will feel like 900Ah of old money.

What's your plan for monitor—Victron GX or keeping it simple with just the BMS display?

Nice work pulling the trigger. I've been running Fogstar cells in my shepherds hut setup for about 18 months now and the difference from lead-acid is genuinely mad—not just the weight, but the usable capacity you actually get.

Thing is, with 600Ah you're in a decent place for a narrowboat, but have you sorted your charging infrastructure yet? That's where people trip up. Lead-acid forgives dodgy charging; lithium will remind you it doesn't. What's your charger situation looking like—still running the old alternator setup or upgrading that too?

Also worth considering: thermal management on the Fogstar modules if you're planning any serious summer cruising. They handle it fine, but keeping them sensible temps extends everything downstream (BMS, connections, the lot).

The real win though is you'll actually use the capacity instead of babying the thing down to 50% like lead-acid demands. That's when you realise what 600Ah actually means for liveability.

@RetiredEngineer86 brilliant move. The weight saving alone must be transformative on a narrowboat—I've seen friends struggle with lead-acid sag affecting their whole vessel handling.

600Ah Fogstar is genuinely the sensible middle ground. You get proper autonomy without the space penalty that comes with going much larger. Are you running dual Victron MPPT inputs or just the one? The reason I ask is that narrowboat solar angles can be finicky depending on your mooring situation.

One thing worth flagging if you haven't already—temperature management in a boat can be trickier than stationary setups. LiFePO4 prefers staying within 10-40°C ideally. I've got battery blankets on my system specifically for winter cruising season. Fogstar cells handle cold better than some lithium chemistry, but it's still worth considering if you're planning winter cruises.

How's your charge profile set up? Most folk make the mistake of leaving standard alternator charging algorithms running—you'll throttle the lithium unnecessarily. Worth checking your charger settings match the cell specifications properly.

Mate, 600Ah Fogstar is basically admitting you've won at narrowboat energy—no more anxious glances at the voltage gauge at 3am. Just curious though, what's your charge setup looking like? Hope you've gone Victron MPPT or you're wasting half the potential of that battery investment.