Orion XS 1400 for cruising sailboat w/AGM start, LFP house and solar

Bit of a different context to most cabin setups here, but I reckon the underlying question translates well — wondering if anyone's running a Victron Orion XS (or similar DC-DC charger) between a start battery and an LFP house bank where solar is also in the mix?

My situation is land-based but the same tension applies: the Orion wants to see the alternator/charger source drop off before it stops pushing current, but if you've got solar keeping the source voltage artificially elevated, the charger can get confused about whether the engine is actually running or not.

Specifically thinking about:

• Whether engine shutdown detection (or equivalent "input voltage drop" detection) is worth disabling when solar is permanently connected to the source side
• How you prioritise charging between the two banks without accidentally flattening the start/cranking battery
• Whether anyone's used the Victron Smart Battery Sense or a proper BMS signal to coordinate this properly

I've got a Fogstar Drift LFP house bank and a fairly basic AGM starter, and I'm trying to work out the cleanest way to let a DC-DC charger handle the split without constantly second-guessing itself when cloud cover causes voltage to bounce around.

Does anyone have a VE.Bus or VE.Smart network pulling this together in a way that actually works reliably? Or is the simpler answer just to wire it sensibly and let the Orion do its thing without overthinking the detection settings?

Keen to hear from anyone who's tackled mixed chemistries with solar in the loop — whether on a boat, van, or off-grid cabin.

@PartnerProject interesting crossover — my setup is static caravan rather than a sailboat but the isolation question is identical.

One thing worth flagging: the Orion XS is non-isolated, which matters if your AGM start bank and LFP house bank share a common negative (hull/chassis ground). On a boat especially, galvanic corrosion risk with a non-isolated unit is worth taking seriously.

For your context I'd genuinely look at the Orion-Tr Smart isolated version instead — more expensive but the galvanic isolation is doing real work there, not just a spec-sheet checkbox.

Questions I'd want answered before specifying anything:

• Are the two banks currently sharing negative?
• What's your alternator output — is the XS's 30A input ceiling actually a limitation?
• Do you need DVCC integration via Cerbo?

The isolated vs non-isolated distinction is probably your most important decision point here.

Running almost exactly this split — AGM starter, LFP leisure bank, Victron Orion XS 30A DC-DC in my motorhome — and the galvanic isolation is the killer feature for a marine environment, not just a nice-to-have.

The XS handles the chemistry mismatch beautifully: AGM alternator voltage won't cook your LFP cells, and your BMS disconnect won't spike the alternator when it trips. A few sailboat-specific things worth considering:

• Engine runtime on a cruiser is often shorter than you'd think, so size the Orion generously
• The Bluetooth monitoring via VictronConnect is genuinely useful when the unit's buried under a cockpit locker
• Pair it with a Cerbo GX if you want proper DVCC integration across solar + alternator

@BlownFuse's isolation point stands double for anything in a saltwater environment — corrosion doesn't care about your budget.

@PartnerProject the narrowboat context is close enough — I've been through exactly this chemistry mismatch problem.

What caught me out initially was the AGM start battery appearing to recover quickly post-engine-start, masking a slow degradation pattern. The Orion XS sorted it properly because it presents the correct absorption profile to each side independently rather than just passing voltage through.

One thing worth noting for a sailboat specifically: the isolated version matters more than people appreciate. Engine alternator grounds and shore power grounds getting tied together through a non-isolated DC-DC can introduce corrosion currents in a marine environment — galvanic issues you really don't want on a steel or GRP hull below the waterline.

I run the Orion XS 50A isolated on my narrowboat and it's been solid. Set it, forget it, monitor via VRM occasionally.

@PartnerProject one thing nobody's mentioned yet — keep an eye on your alternator situation. Marine alternators on sailing boats often aren't sized for the kind of sustained draw an LFP bank will happily pull through a DC-DC charger. The Orion XS is brilliant but it will work your alternator hard.

My land-based setup taught me this the embarrassing way. Victron's input current limit feature is your friend here — throttle it back until you know what your alternator can handle comfortably.

Also worth checking: is your AGM start battery on a dedicated charging circuit, or does it just get topped up via isolation diode? The Orion XS needs to see the AGM bank properly to trigger correctly. Sailboat wiring being what it is... 🙃

What alternator are you running?

Worth flagging that on a sailing boat your alternator's getting a proper workout every time you motor — the Orion XS's built-in current limiting is basically doing your alternator a favour while simultaneously sorting the AGM/LFP chemistry mismatch, two birds one stone and all that. Had similar concerns fitting mine in the van before I trusted it to just get on with it. Also worth checking whether your boat's alternator has a smart regulator already — if it does, you'll want to make sure the Orion XS input settings don't fight it. Fogstar do decent LFP cells if you're building your house bank rather than buying pre-built, saved me a fortune over branded drop-ins.