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VE.Bus BMS and MultiPlus / Cerbo combination

I have wanted to be able to control the Multiplus via the Cerbo, but the VE.Bus BMS and VE.Bus BMS Assistant on the Multiplus block the Cerbo from changing the invert state between On / Off / Invert Only / Charge Only.

Having done some testing I have reverted to the 2-Wire BMS assistant on the Multiplus and wired the VE.Bus BMS Charge Disconnect to the Aux 1 port and Pre-Alarm to Aux 2, using an Inverting remote on-off cable. I am now able to change the status of the Multiplus from within the Cerbo Screens. The Cerbo correctly shows the VE.Bus BMS status through the relevant MultiPlus screen. Both disconnected at the moment.

I also had a VE.Bus Smart Dongle and found I could modify the status of the Multiplus via my phone as well. When status changed the Cerbo reflected that changed status. So I have a system working as I would like, but not using any functionality of the VE.Bus. I guess I could have achieved the same thing using the smallBMS with pre-alarm.

What I was wondering is if anyone can advise what functionality I might have lost by disconnecting the VE.Bus BMS from the VE.Bus?

I have noticed during my testing today that there is no Alarm or Error that is logged when the VE.Bus BMS signals load or charge disconnect, simulated by disconnecting the signal. The Cerbo clearly isn't triggering on the change of the Multiplus VE.Bus BMS status. I am not sure if it ever did alarm/alert when the VE.Bus BMS was connected via the VE.Bus port to know if I lost functionality. I do know a few weeks back I had a VE.Bus BMS Charge disconnect event and never saw anything on the Cerbo.

Hope people find this useful and it would be good to understand what functionality has been lost by taking this approach and not have the VE.Bus BMS communicating on the bus.

MultiPlus Quattro Inverter ChargerVenus OSBMSVE.BusVE.Bus Smart Dongle
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It would be really nice if vicron fixed this as not being able to remotley turn the inverter on and off remotely when a VE-BMS and assistant are connected to a system is quite a issue. and I cant see the logic as to why it cant be allowed

I have deep dived and done a fair amount of testing and like you cant see what is creating the issue. I have read statement on this forum from Victron stating it is complex and if they could fix it, they would have.

I have some more testing to do over my next few visits to the boat, to understand more about the problem.

If it is an issue with the VE.Bus BMS and hardware related, I'd by a new one just to get it to work. The DMC does not deliver the functionality needed, as it cant interact with MQTT, Node Red, etc.

I am possibly moving to a smallBMS so that I at least get control. The only downside seems to be the loss of sending the MultiPlus into a deep sleep on load disconnect and loss of mains. There is however a downside off deep sleep, in that the VenusOS looses CD and LD information and cant supply signals to the Smart Solar via VE.Direct or CanBUS to allow charge. So using the smallBMS does mean the signals are still available at a high parasitic load and risk of draining batteries flat should solar fail !

Yes its a very annoying short coming at times, but it is what it is and we just have to live with it.

Did some more testing today. Compared VE.Bus BMS assistant and 2-Wire BMS Assistant. The 2-Wire allows VenusOS to change the state of the MultiPlus, while the VE.Bus BMS Assistant does not,

Looking at the GUI code, it is a single dBus elect called 'ModeIsAdjustable' which changes the behaviour. This is clearly set within the mk2-dbus driver, which is the interface between VE.Bus and VenusOS. I cant work out the logic as to why this is set. I can understand it when the DMC is in the system, but not when one isn't.

There is no rhyme no reason as to why this is set to allow changes for the 2-wire, but not for the VE.Bus......

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