Démarage du monde chargeur de batterie du multiplus automatiquement en fonction du SOC par BMV712!

Been thinking about this a lot lately with my shepherd's hut setup — has anyone got their BMV-712 triggering the Multiplus charger automatically based on SOC thresholds?

My current system is fairly modest compared to some rigs I've seen discussed:

• 8 x 200W panels (Renogy)
• Victron Multiplus 12/3000
• Single MPPT 100/30
• BMV-712 doing the monitoring
• Cerbo GX tying it all together

What I want is for the Multiplus to kick in mains charging automatically when SOC drops below, say, 40% during a run of bad weather — then cut out again once it hits 80% or so. Essentially letting the BMV-712 call the shots rather than me manually faffing with it.

I know the Cerbo GX can handle a lot of this logic through ESS or relay settings, but I'm not 100% sure whether the BMV relay output can directly talk to the Multiplus in a meaningful way, or whether it all needs to go through VE.Bus and the GX device.

Anyone running a similar hybrid arrangement — particularly with grid or generator hookup as a backup source? Curious whether you've configured this through VEConfigure, the VRM portal, or just the GX touch screen.

Also interested to hear from anyone using Fogstar or other lithium banks — does the BMS throw any spanners in the works when the Multiplus tries to auto-start?

Would be good to get a proper thread going on this rather than digging through five-year-old posts that predate half this kit.

@DodgyHermit yes, running exactly this on my shepherd's hut setup.

The BMV-712 has a relay that you can configure to trigger on SOC thresholds — I've got mine set to close at 50% SOC and open again at 90%. That relay signal feeds into the Multiplus aux input to kick the charger on/off automatically.

In VictronConnect you'll find it under Relay settings — set it to State of charge mode, define your low/high thresholds, done.

Few things worth noting:

• Make sure your Multiplus is configured to respond to the aux input correctly in VEConfigure
• Hysteresis is your friend — don't set thresholds too close together or it'll cycle constantly
• If you've got a Cerbo GX or similar in the chain, you can do more sophisticated logic via Node-RED instead

What batteries are you running? Makes a difference to where you set those thresholds.

@DodgyHermit done exactly this in my shepherd's hut — set the BMV-712 relay to close at 30% SOC and open again at 80%, wired straight into the Multiplus aux input, and it just gets on with it while I drink tea and pretend I'm a farmer.

@OffGridHamish @24VGeek done the same on my static but also wired the relay through a basic timer so the genny doesn't fire up at 3am when the SOC drops — neighbours already hate me enough without adding that to the list.

Worth noting the BMV-712 relay is potential-free, so you'll need a proper interface relay if you're triggering the Multiplus generator input directly — learned that the hard way with some creative smoke.

Also set a minimum voltage floor as a backup condition alongside SOC, because if your Fogstar cells ever develop cell drift your SOC reading becomes about as reliable as a British summer.

@NotAnElectrician80 worth noting the BMV-712 relay is a dry contact rated at a fairly modest 3A — so make sure you're not driving anything directly from it that'll exceed that. Run it through a proper intermediate relay if you're switching anything beefy.

Also, the "auxiliary relay" function in the BMV settings is what you want — specifically the relay mode set to "SOC". There are separate low/high SOC thresholds for open and close, which gives you the hysteresis you need to stop it chattering on and off constantly.

@OffGridHamish what charge algorithm have you got set on the Multiplus side? If the BMV is cutting the relay before bulk's finished you'll end up with chronically undercharged cells over time — worth watching your actual voltage at relay-open, not just the SOC figure.