Low Voltage Warning trying to use Fogstar Lithium with Phoenix Multi Plus 3000/120/12

Bit of a head-scratcher this one and wondering if anyone else has hit the same wall.

Fitting out a narrowboat for a mate and we've swapped his tired old lead acid bank for a Fogstar Drift 200Ah (the Gen 1, not the newer one). Paired with a Victron MultiPlus 3000/120/12 — should be a dream combo in theory, shouldn't it?

The problem is we're getting low voltage warnings and occasional cutouts under heavier loads, even when the battery is showing a decent state of charge. The MultiPlus was previously running fine with the old lead acids, so I'm fairly confident the inverter itself isn't the issue.

My suspicion is the charge profile settings — the MultiPlus still seems to be running parameters suited to AGM/flooded batteries rather than lithium. Could that be causing enough of a voltage discrepancy to trigger the warnings?

A few things I'm wondering:

• Does the Fogstar Drift Gen 1 need a specific BMS communication setup, or is it purely standalone?
• What absorption/float voltages are people using for this battery on a Victron system?
• Is there a minimum current draw threshold where the MultiPlus just gets jittery with lithium?

The boat is essentially a liveaboard so reliability isn't optional — this can't be cutting out when someone's running the kettle at 11pm in the middle of nowhere on the Llangollen canal! 😅

Has anyone successfully married these two bits of kit on a narrowboat or similar setup? Would love to know what settings you landed on before I spend another afternoon elbow-deep in the engine bay.

@HollyGaz classic Victron/lithium handshake drama — the MultiPlus is almost certainly still set to lead-acid charge profile and throwing a low voltage tantrum because the absorption/float thresholds are miles off for lithium.

Jump into VE.Configure and set:

• Absorption: 14.2V
• Float: 13.5V
• Low DC cutoff: 11.5V (Fogstar Drift BMS handles the real protection anyway)

Also check your Battery Type is set to Lithium in VE.Configure or it'll keep second-guessing itself.

If you've got a Cerbo GX or VE.Bus Smart Dongle on there, the DVCC settings matter too — enable it and let the BMS talk properly.

Fogstar's own docs suggest these figures, and I've run near-identical config in my motorhome without a grumble since.

@MarineGeoff nailed the profile thing, but also check your low voltage disconnect in VEConfigure — default is something daft like 10.5V which sounds fine until you realise Fogstar's BMS will hard-disconnect around 10V anyway, so you're basically letting the MultiPlus flap around in no-man's-land before the BMS even gets involved 😅 Had exactly this chaos in my van build last winter. Set your absorption to 14.2V, float to 13.5V, and bump that low disconnect up to 11.8V so the MultiPlus backs off before the BMS throws a wobbly — saves your loads from the sudden cutoff.

Both @MarineGeoff and @VoltMax are on the right track, but there's another sneaky one that caught me out on my own narrowboat build last spring — the dynamic current limiter in VEConfigure.

With lithium the MultiPlus can momentarily see a voltage dip during load spikes and panic, even when the battery is healthy. Worth checking the AC input current limit isn't set too conservatively as well.

The Fogstar Drift's BMS is also quite aggressive at protecting itself — if VEConfigure is still sending bulk charge voltages above 14.6V it'll trip the BMS before the MultiPlus even knows what's happened, which looks like a low voltage fault but isn't really.

Victron have a lithium assistant you can load through VEConfigure — genuinely worth ten minutes of your time before chasing hardware gremlins.

Had this exact same issue on my van build with a Fogstar Drift. One thing nobody's mentioned yet — check your assistant settings in VEConfigure too, not just the main charge profile. If he's got the lithium battery assistant loaded but it's still referencing old voltage thresholds, it'll throw low voltage warnings even when the battery is genuinely healthy.

Also worth double-checking the battery capacity setting in VEConfigure matches the 200Ah — if it's undersized from the previous lead acid bank the MultiPlus can get confused about state of charge calculations and trigger warnings prematurely.

Fogstar Drift BMS is pretty solid in my experience, so I'd rule out the Victron config before assuming it's a BMS comms issue.