Ongoing issues with charging with Multiplus II 24/3000/70 and XS1400

Been wrestling with something similar on the narrowboat for the past few weeks and wondered if anyone else had hit the same wall.

Running a Multiplus II 24/3000/70 alongside a Sterling Power BB1230 balancer and an Orion-Tr 24/12-20 for the 12V domestic side. Works a treat most of the time, but I'm getting some odd behaviour when the XS1400 (alternator regulator) is trying to charge simultaneously with the Multiplus on shore power.

Basically the two seem to argue with each other. The Multiplus will be happily bulk charging, then the engine kicks in, the XS1400 joins the party, and I'll get voltage spikes that are making my BMS nervous. She'll occasionally trip out entirely, which on a boat in a lock is... not ideal.

My suspicion is that the charge profiles aren't playing nicely together — the XS1400 is quite aggressive in its absorption phase and I don't think the Multiplus backs off gracefully when it detects another charge source.

Has anyone managed to get these two properly coordinated? I've been digging through VEConfigure trying to find a way to soften the Multiplus response but I'm going around in circles a bit.

Also curious whether anyone has gone down the route of disabling the XS1400's voltage sensing and just letting the Multiplus lead — seems like the logical solution but I'd be sacrificing some alternator protection I'd rather keep.

Running Fogstar Drift lithium cells with a Daly BMS if that's relevant. Solar going on the roof come spring, which'll only add another layer of complexity to the whole thing.

Hey @Jonno, narrowboat setup here too so very familiar with the Sterling BB range quirks!

One thing worth checking that catches people out - the XS1400 has a fairly aggressive current limiting behaviour when it detects certain charge profiles from the Multiplus II. Have you verified your DVCCs settings in VenusOS? Specifically the SVS (Shared Voltage Sense) toggle - if that's fighting with the Sterling's own voltage sensing you can get some really odd charge termination behaviour.

Also worth checking whether your battery temperature sensor is seated properly on the cells rather than the casing - seen this cause phantom BMS trips on a mate's boat up at Braunston.

What firmware are you running on the GX device? Some of the earlier 2.9x builds had gremlins with certain BMS comms. 🚢

@Jonno what's the actual charge voltage the Multiplus is targeting vs what the XS1400 is set to? I had a similar headache sorting comms between mismatched chargers in my garden office build — ended up being a subtle absorption voltage mismatch that was confusing the BMS into thinking there was a fault when there wasn't.

Also worth checking — is the BB1230 set to priority charge mode? If two charge sources are fighting over who's "in control" it can cause the kind of instability you're describing.

What BMS are you running on the 24V bank? If it's outputting a DVCC signal via Victron's VE.Bus, that might be overriding one of the charger's parameters unexpectedly.

@Jonno had a very similar fight getting my Multiplus II to play nicely with a DC-DC charger on the garden office setup.

The classic culprit here is the two chargers essentially "arguing" — the XS1400 sees the Multiplus already raising battery voltage and backs off, then vice versa. Net result is neither charges properly.

A few things worth checking:

• Set the XS1400 to a slightly lower absorption voltage than the Multiplus so it defers cleanly
• Make sure your DVCC settings in VictronConnect are actually enabled and configured correctly if you're on a Cerbo/CCGX
• Check the XS1400's input voltage sensing — if it's reading alternator voltage rather than battery, it'll behave oddly

What BMS are you running? If it's sending charge current limit signals that's another layer to untangle.

Really interesting thread — I've got a Multiplus II (12V version, mind you) in my garden office and wrestled with integration issues for months.

One thing nobody's mentioned yet: have you checked whether the XS1400 is seeing the Multiplus's bulk/absorption cycles and reacting to them? Sterling's B2B chargers can sometimes interpret voltage spikes during Multiplus charge transitions as "battery full" and back off prematurely.

What comms setup are you running between the Multiplus and your BMS? If you've got a Victron DVCC setup going through Venus OS, it can sometimes fight with the Sterling's own voltage-sensing logic — essentially two things trying to be "in charge" simultaneously.

Might be worth logging both devices separately and overlaying the voltage/current graphs to spot exactly where the disagreement kicks in. VictronConnect makes the Multiplus side easy enough to capture.