Swapped to lithium on my 26ft Beneteau – worth every penny or am I imagining it?

Never done it on a boat, but swapped my shepherd's hut over to a pair of Fogstar Drift 100Ah cells last spring and the difference was so obvious I stood in the doorway like an idiot just watching the voltage hold steady.

The "am I imagining it" phase is real — your brain keeps waiting for the sag that never comes.

A few things worth considering if you haven't already:

• BMS compatibility with your existing Victron kit (if you're running any) — the DVCC settings on a Cerbo GX need a poke if you're going lithium
• Charging profile on your alternator — unprotected alternators and lithium are a spicy combination on boats where you're doing longer engine runs
• Weight distribution — obviously less relevant in a hut than a Beneteau, but lithium being roughly half the weight of AGM might shift things more than you'd expect at the bow

The real question nobody asks is whether your solar controller was already quietly throttling you on AGM — mine was, and I'd never have known without the switch.

Curious what capacity you've gone to and whether you kept your shore power setup as a backup, or binned it entirely? I'd imagine coastal mooring adds a few variables that a static cabin like mine doesn't have to deal with.

@SaltyTrekker not imagining it at all — did the same swap on the narrowboat a couple of years back and the "standing in the doorway" feeling is very real 😄

The usable capacity difference is what gets you. Two 100Ah Fogstar Drafts actually give you ~200Ah usable rather than the ~100Ah you were tiptoeing around with AGM. Feels like a completely different system.

One thing worth checking on a Beneteau — your shore power charger settings. A lot of marine chargers default to AGM profiles and will either undercharge or just confuse themselves with lithium. Had to reprogram mine before it played nice. Victron stuff tends to sort itself, but older OEM chargers can be a pain.

@HighlandDweller

Done a similar swap on my off-grid cabin rather than a boat, but the physics is the same — you're suddenly actually using that bottom 50% of capacity you were always leaving on the table with lead acid. On a 26ft Beneteau that's going to feel transformative, especially if you're running a chartplotter, VHF and cabin lighting through the night at anchor.

One thing worth mentioning for the marine context specifically — keep an eye on your alternator setup. Lithium will happily flatten a standard alternator if you've not got a proper DC-DC charger in the circuit. Victron Orion is what most folks round here seem to land on. Learned that one from a thread here before I made any mistakes myself!

Which BMS did you end up going with?

@DaleBen

@SaltyTrekker definitely not imagining it — the usable capacity difference alone makes it feel like you've doubled your bank. With lead-acid you're nervously stopping at 50%, whereas with lithium you're comfortably running down to 80-90% DoD without a second thought. On a Beneteau that's probably the difference between running your nav electronics and fridge overnight versus rationing everything after sundown.

One thing worth mentioning for the marine context specifically — check your alternator isn't going to throw a fit with the lithium charge profile. A few lads have had issues with older alternators seeing the flat voltage curve and essentially flogging themselves to death. A decent DC-DC charger between the engine and your lithium bank sorts it properly. Fogstar Drift cells are cracking value for the money as well — solid BMS from what I've seen.

Done the same on my static and a motorhome — and honestly the thing that gets me every time is how the voltage holds flat right across the discharge curve. Lead acid is constantly sagging, you're never really sure what you've got. Lithium just... doesn't do that.

@SaltyTrekker marine environment though — worth double-checking your BMS is rated for the humidity/temp swings if you haven't already. Fogstar Drift cells are solid but a damp bilge is a different world from a shepherd's hut.

Also if you're on a Victron setup, make sure DVCC is configured properly — boat installs seem to catch people out more than van builds for some reason. Had a mate with a trawler who had constant absorption issues until he sorted that.