Narrowboat solar on a 12V system — worth going 24V for a longer liveaboard setup?

Been helping a mate spec out his narrowboat conversion and we've hit the classic crossroads. He's running a 12V system at the moment — 200Ah of Fogstar Drift lithium, a Victron SmartSolar 100/30, and about 400W of panels on the roof. Works fine for weekend trips but he's now talking about spending 2–3 weeks at a stretch on the cut without shore power or a generator.

The cable runs on a narrowboat are long. We're talking 6–8 metres from the battery bank to the inverter, and another good stretch to the bow thruster. At 12V that's a real headache for voltage drop, even with chunky cable. Moving to 24V would halve the current and make the whole thing a lot tidier — but it means swapping the Victron unit, redoing the battery bank, and touching basically every circuit.

His daily consumption is rough: about 80Ah on a quiet day, 120Ah when he's got the induction hob running off the inverter. A proper liveaboard setup would want at least 400–500Ah usable, maybe more. At 24V that's suddenly much more manageable weight and cost wise if he goes with two pairs of 200Ah cells in series-parallel.

Has anyone here actually made the jump from 12V to 24V on a working narrowboat? Curious whether the rewiring grief was worth it, or whether you just threw more capacity at the 12V system and called it done.

Hey @DontPanic25, worth knowing that the 100/30 is already pushing its limits on a decent 12V solar array — you're capped at 30A charge current regardless. If your mate's planning to expand panels significantly for full liveaboard use, jumping to 24V effectively doubles the usable wattage through that same controller. Also worth considering cable runs on a narrowboat — 24V halves your current, which means you can get away with lighter cabling over those longer bow-to-stern distances without the voltage drop headaches. The Fogstar Drift cells can be reconfigured to 24V too if he bought individual cells rather than a pre-built pack. Main downside is having to replace any 12V-only appliances, though most decent inverters and DC-DC converters handle the transition fairly painlessly. What's his rough daily consumption looking like?

Made the jump to 24V on my static and never looked back — lower current means thinner (cheaper) cable runs, less heat, and your MPPT headroom opens right up.

For a liveaboard narrowboat I'd seriously consider it. Inverter efficiency improves too, especially if he's running anything substantial like a compressor fridge or induction hob.

The main faff is the battery side — he'd need to either replace or series the Fogstar packs. Fogstar are good about compatibility specs, worth checking their docs directly.

Victron's SmartSolar 100/50 at 24V gives him a solid upgrade path without replacing the MPPT controller entirely. And a Multiplus-II 24/3000 later down the line is a cracking bit of kit for a liveaboard setup.

Short answer: if he's serious about long-term liveaboard, 24V now saves headaches later. 🔋