BMS VE.Direct port conundrum

DIY
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1

Hi all,

I just upgraded to LiFePO4 batteries and installed a VE.Bus NG BMS. I also have a solar panels run by a SmartSolar controller, which is currently connected to my CerboGX via the SmartSolar’s VE.Direct port.

In order for the BMS to control my solar charger (i.e. shut it down in the event of battery overcharging or overheating) I need to connect the BMS to the SmartSolar controller’s single VE.Direct port; this means disconnecting it from the CerboGX and losing all visibility of my solar charging from the VictronConnect app.

Is there any way to have my cake and eat it too, i.e. connect the SmartSolar unit to both the BMS (for shutdown) and the CerboGX (for visibility)?

Thanks in advance for any advice,

  • Dave
2

You do not mention a VE Bus inverter, I assume you have / plan to have one as the BMS gets its power from tje inverter via the VE Bus cable.

Have a thorough read of the VE Bus BMS manual. The BMS should be connected to the Cerbo via VE Bus cable, the BMS then tells the Cerbo to stop charging, the Cerbo then tells the MPPT to stop charging via the VE Direct cable using the DVCC function. The MPPT charge parameters need setting for the NG batteries.

Section 3.3.4 describes this.

There is not a system example of this, so wire according to Section 3.1.2 and connect the MPPT by VE Direct.

3

Thanks @pwfarnell, everything you mention is already in place, including the appropriate cables. My problem, to clarify my original question, is that the SmartSolar MPPT only has one VE.Direct port, which I can use either to connect to the CerboGX or to the NG BMS - but apparently not to both at the same time. This means the MPPT can be controlled by the BMS, or else the MPPT can send info to the CerboGX - but not both. I’m hoping there’s a way to get around this problem and have my solar performance visible on Victron Connect but also let the BMS control solar charging, for safety reasons. Let me know if you have any solutions for this conundrum!

  • Dave
4

Yes, I know exactly what your question is and I had tried to answer it and point you at the manual.

Connect the MPPT to the Cerbo GX via VE direct so the Cerbo reads the MPPT.
Do not connect the BMS ATC port to the MPPT.
Connect the VE Bus BMS to the Cerbo via VE Bus.
Enable DVCC on the Cerbo.

Read the Cerbo manual about DVCC.

This is how it works.

  1. There is a battery problem.
  2. The BMS tells the Cerbo to stop charging.
  3. The DVCC function on the Cerbo tells the MPPT that charging must stop by setting the charge current limit (CCL) to 0.
  4. The MPPT stops charging.

You can have your cake and eat it.

1 Like
5

The Cerbo GX has multiple VE-direct ports, Connect one to the solar charger, and the other to the BMS. Then make sure that the DVCC is on (it should be forced on). The BMS will the cause the GX device to control the Solar charger.

6

[Updated}

Thanks, Mike. The Multiple Victron comm protocols and interfaces are a bit confusing, even to a (retired) network engineer like myself!

So if I connect my MPPT to the CerboGX using a 4-pin VE.Direct cable, and connect my BMS to the CerboGX using an RJ45 cable (VE.Bus?), will that allow the BMS to control the MPPT? In other words, can the Cerbo receive a ‘stop charging’ request from the BMS via VE.Bus and then send it to the MPPT via VE.Direct?

The BMS manual just shows the BMS connecting directly to an MPPT using a special VE.Direct cable that converts between the MPPT via VE.direct and the MBS Charge Disconnect port, so I assumed that was the only option…

  • Dave
7

Yes that will work.

Yes, that is described in Section 3.3.4 of the manual. But as I wrote above and per the manual DVCC must be enabled on the Cerbo for this to work. The Cerbo manual describes DVCC.

Cerbo manual DVCC section

You can test it once the system is set up by disconnecting one of the M8 battery comms cables from the BMS.

8

Thanks PW. I’d already tried disconnecting the M8 BMS connection when I first installed the new batteries and the Multiplus stopped charging, so I assume that means DVCC is working. However I just tried disconnecting again with solar charging in progress, and although the Multiplus once again recognized the disconnection, there was no effect on the solar charging - it continued bulk charging. Any idea what’s missing here?

9

No, that should have stopped charging if DVCC is active.

However, the VE Bus BMS will talk direct to the Multiplus, you do not need the Cerbo to control the Multiplus and the Multiplus is controlled without DVCC.

Therefore, you need to go into the Cerbo GX settings and check that DVCC is enabled.

People on here report that with a correctly configured system that removing an M8 connector does stop solar charging.

10

Thanks for the explanation - looks like everything’s working now. When I unplug the M8 connector the solar charger stays in Bulk mode but drops down to 0.5a current. Plug it back in and it goes back up to ~10a.

Thanks for your patience in walking me through this!

  • David
11

I just realised I was answering you on 2 different topics.

Your reply has made me recall that when the MPPT is under external control by DVCC it often reports bulk regardless of what it is doing.