Remote On/Off Switch for Inverter w/ VE.Bus BMS NG

Been scratching my head over this one for my garden office build and could do with some collective wisdom.

I'm running a Victron Multiplus-II with the VE.Bus BMS NG and I'm trying to work out the cleanest way to wire in a physical remote on/off switch for the inverter. Seems straightforward on paper, but every thread I find online ends up going down a rabbit hole about whether the BMS NG handles the remote L/H signal differently to the older VE.Bus BMS.

A few specific things I'm unclear on:

• Does the BMS NG's charge disconnect and load disconnect behaviour interfere with the remote switch wiring at all?
• Is it safe to use the remote on/off terminals directly, or does everything need to go through an Assistants configuration in VEConfigure?
• Has anyone used a simple rocker switch vs a smart relay here — is one approach more reliable?

I've got Fogstar Drift lithium cells with the BMS NG sitting between them and the Multiplus, so I want to make sure I'm not accidentally overriding any battery protection logic by wiring this up wrong.

The Victron documentation is decent but feels like it was written for someone who already knows the answer, if that makes sense. There seem to be a few valid approaches and I genuinely can't tell which one applies to my setup.

Has anyone done this with the BMS NG specifically (not the older VE.Bus BMS)? Would love to know what wiring approach worked for you and whether there were any gotchas along the way.

@Liz1979 looks like your post got cut off — finish the question and we'll dive in properly!

That said, I can probably guess where you're heading. With the VE.Bus BMS NG controlling the Multiplus-II via the BMS Assistant, the remote on/off behaviour changes significantly compared to older setups. The BMS NG takes authority over the charge/invert states directly, so any additional remote switch needs to sit on the right side of that hierarchy or you'll end up fighting the BMS logic.

The key thing to establish is what you actually want to switch — just the inverter function, or the whole unit including charging? Those need different approaches. The two-wire BMS connection on the Multiplus-II's remote terminal is worth reading up on in Victron's DVCC documentation before you wire anything.

Post the full question and I'll try to give a more specific answer based on what I've done on my own motorhome build.

@Liz1979 the VE.Bus BMS NG handles the remote on/off via the Allow-to-Charge / Allow-to-Discharge signals directly — it'll pull the Multiplus-II down itself if the battery kicks off, so you don't wire a manual switch into the remote L/H terminal like you would on older setups, unless you want a physical override, in which case you stick it in series on the Remote on/off connector (pins 1 & 2) with a simple DPST switch.

Had exactly this faff on my static caravan build — spent an afternoon reading the wrong BMS manual before realising NG changed the wiring convention entirely compared to the original VE.Bus BMS.

Check the Victron VE.Bus BMS NG datasheet — page 4 has the connection diagram and it's actually clearer than most of their docs.

@Liz1979 to build on what @Rob1963 started — the key thing people miss is that the VE.Bus BMS NG uses a two-wire control system rather than the older single-wire approach. The "Allow to Discharge" signal directly controls the Multiplus-II's inverter function via the remote on/off terminals on the left-hand side of the unit.

If you want a physical remote switch on top of that BMS control, you need to wire it in series with the BMS NG's allow-to-discharge output — never bypass it entirely or you'll lose your battery protection. Victron's own wiring diagram (CCGX section of the MPII manual) shows this clearly.

Worth noting: a plain rocker switch won't cut it here — you need to respect the open collector logic. A decent relay or just use Victron's own remote panel.

@Liz1979 to add something none of the others have touched on yet — if you're wanting a manual remote on/off on top of the BMS NG's automatic protection signals, you need to be careful not to conflict with the two-wire control logic @DailySolar mentioned.

The Multiplus-II has a dedicated Remote on/off connector (2-pin) on the unit itself. With the VE.Bus BMS NG in the loop, I'd strongly recommend using a RJ45 UTP cable with an assistant configured in VEConfigure rather than wiring anything directly to that 2-pin — otherwise you risk overriding BMS disconnect events.

In my own setup I use a Cerbo GX with a physical switch wired to a digital input, configured as a generator start/stop signal, which then controls the inverter state cleanly without fighting the BMS. Keeps everything within the Victron ecosystem and fully logged.