Made a similar switch on the narrowboat last autumn — swapped out the tired old AGM bank for a pair of Fogstar Drift 100Ah LiFePO4 batteries wired in parallel, keeping my Victron MultiPlus-II 12/3000 in place.
The dip switch rabbit hole is real. On older MultiPlus units there's a temptation to just flick the lithium preset and call it a day, but that only gets you so far. The proper way is through VE.Configure (or VictronConnect if your unit supports it) where you can actually dial in:
- Absorption voltage — around 14.2V for most LiFePO4 rather than the 14.4–14.7V you'd run AGM at
- Float voltage — I dropped mine to 13.5V
- Charge current limits — important if your BMS has a ceiling
The thing that caught me out was the battery type setting in VE.Configure. Leaving it on "gel" or "AGM" and just tweaking voltages can work, but you lose some of the smarter charge behaviour. Setting it to "lithium" properly disables the absorption time limits which matters more than people realise.
Also worth checking whether your BMS talks to the Cerbo or CCGX via VE.Bus or canbus — if it does, you can hand charge control over entirely to the BMS which is the cleanest solution.
Anyone else running a MultiPlus-II on a boat with a canbus-capable BMS? Curious whether people are letting the BMS drive things or still managing it manually through the Victron side.
