Multiplus - BMS Lost, Battery Low

DIY
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1

Multiplus Master & Slave 24/5000/120, 4x24V 200AH Victron LiFEPO4, Lynx Distributor & BMS, 5 x Victron MPPTs, CerboGX on a boat connected to shore power when required.

Whilst watching TV last night I suddenly lost all AC power on the boat whilst the Multiplus’s were in inverter mode. Messages received Low Battery warning then BMS Lost. SOC at the time was 84% and only “significant “ draw was the TV. It was dark so no MPPT influences however at first light today I got error codes #67 No BMS, on the Solar Chargers.

Trouble shooting involved taking each of the cables off the Lynx, checking voltages, checked all fuses for continuity, checked voltages on removed input cables to the Multiplus and at the isolation switches. All voltages 26.39 +/- 0.01.

VEConfigure indicates correct configuration.

All RJ45’s disconnected then reseated, then MPPT’s VE can cables removed leaving only LYNX , Multiplus and Cerbo linked. Swapped Cat 5 cable between Multiplus’s out.

LED lights on the Master - Mains (steady), Battery Low (dull but steady).

LED on the Slave - Mains ON and Inverter ON alternately blinking and Battery Low steady bright.

Multiplus’s configured Charger DC Input Low Shutdown 18.60V, Restart & Pre Alarm 21.80, Charger Absorption 28.40, Float 27.00, Charge current 90.

None of the above actions remedied the situation. I couldn’t find any other offered solutions in the many posts. No work has been done on the system in a long time and the boat has been in the marina unmoved for nearly 5 months.

Cerbo updated to 3.70 and any requested updates were completed.

So question is the Lynx potentially at fault or a Multiplus?

Should I revert to single Multiplus and try that? Like others I have had periodic BMS lost messages especially with the MPPt’s which generally clear OK. I am currently operating in Pass Through mode so batteries are being charged that way. A solution to this would be greatly appreciated afer a day of engine room yoga and go fetch. TIA.

2

Try reverting to previous Cerbo version - 3.66 or 3.67 (that’s what fixed it for me!)

3

Thanks. Problem is I was on 3.67 when it occurred and I updated hoping that would improve things. Good thought though as It worked for me with another issue.

4

This sounds to me like the main MP is waiting for ACin with its inverter off, and the second MP is signalling that its the slave. But battery low additionally indicates that they both receive too low of a battery voltage.

But did you measure the DC voltages on the input terminals of the MPs?

The MPs in Passthrough would mean they neither charge or discharge the batteries. But this also means that you got ACin and they both switched to that, so check the status LEDs again.

If you have a cerbo, check if it has any errors logged

5

Thanks Chrigu. I am appreciating your help. Sorry I forgot to mention specifically that DC voltages at the MP’S also are correct when cables removed and checked.

Initial messages on Cerbo as below. At the time I isolated each MP then turned them each on and off to see if I could reset the system.

Screenshot_20260301_174849_Chrome
Screenshot_20260301_174849_Chrome2340×1080 148 KB

6

Checking Cerbo, it says it hasnt seen the BMS for 2 days. Is this my issue? If so what might re.edy this apart from replacement please?

Screenshot_20260302_101714_Chrome
Screenshot_20260302_101714_Chrome1080×2340 151 KB

7

Further wrestling with the system without success, in fact worse off now.

Tried soft reset of VE bus on the cerbo. No change.

Removed all mppts from the system disconnecting ve directs and cans to cerbo.

Turned MP’s off. Disconnected shore power and battery cables from both multipluses. Waited 5 minutes then reconnected batteries turned MP’s back on. Same. :frowning:

New cable cerbo ve bus to master MP. New cable MP master to MP Slave.

Connected cerbo BMS can to Lynx Smart BMS.

Enabled VE Can Port to profile VE Can & Can-Bus BMS (250 kbit) . I can’t find anything written on this but thought it should be enabled. ???

Enabled BMS Can Port to profile CAN BUS LV. Again disabled but thought may be should be enabled.

Reset VE Bus each time.

Current Status

Master Led – Battery Low (steady), Slave Battery Low (steady) and Float blinking

Connected Mk3 disconnecting cerbo from multiplus master

Master - Battery Low (steady) and Inverter ON/ Absorption On alternate blinking

VE Config screenshots

VECON slave3
VECON slave31723×847 253 KB

VECON slave2
VECON slave21660×973 290 KB

VECON Master3
VECON Master31681×972 280 KB

VECON Master2Inv
VECON Master2Inv1705×880 261 KB

Now I have cerbo reporting shore connect/ disconnect with or without shore power connected so no sustained pass through now. Note this now continually cycles. See vid below.

So now I am left with a reinstallation of firmware and or veconfig? Running out of ideas. TIA

8

The gift that keeps giving!

With the shore power cycling on and off still, I decided to try the Master MP as standalone and see what effect that had. Having reconfigured to standalone in VEconfigure I got the following screen. I did get Mains on led steady but also Battery Low steady. Interestingly I noticed the VE Monitor showed UDC at 18.5V whereas in parallel it showed as 26.1V.

MasterStandalone1
MasterStandalone11693×1009 306 KB

Unfortunately the shore power oscillated on and off a couple more times and I lost the Master MP all together with no lights and no VEconfigure response.

So no pass through and no parallel reversion.

I attempted to apply the VEconfigure to the previous slave and whilst the Mk3 is detected, it wont open up the port on the Slave. Any ideas here please?

Starting to run out of options. Any help gladly received if only to confirm the MP/s are stuffed and need fixing. Do I need to open a ticket?

9

It is probably time to find a capable installer to help you figure this out. It is most likely a config or installation issue.
The community can’t help you with support but if you follow the link in our guidelines to support that would start the process.

10

Thanks Nick. I’d like to think it was a config or installation issue, however the system has been stable for a good couple of years so that doesn’t make sense to me. I am hoping the community might have been able to point to me where to look given the previous stability and out of the blue stoppage and being reasonably handy. Given also the number of others experiencing BMS lost issues over the last few years, I thought my experiences, others suggestions and my work throughs might be of assistance to others.(?)

My installer has proven unhelpful in the least in the past which given previous experience is where Victron tells me to head.

11

Then it’s best to take them to someone who can properly bench test them.
There is a documented process you can also follow prior to taking them in.

12

Ok. Thanks Nick. So just so I’m clear, are the symptoms pointing to both MP’s at fault? I can see the Lynx Smart BMS locally but not on Cerbo. Its parameters appear fine.

13

If the lynx is not visible on the Cerbo, this won’t work properly.
You either have a comms issue (cable, terminators etc) or something has broken on either the lynx or cerbo, preventing comms.
Make sure it is in the right CAN port and the correct profile is set.
If the GX can’t see the BMS, nothing else will.

14

Thanks again. In my troubleshooting I had moved my Cerbo to Lynx BMS to the BMS Can on the Cerbo. It is back in the VE Can slot and working fine.

Presupposing it is only the Master MP that is at fault, I want to delete it from the system and make the old slave the new master as standalone until I get the Master MP repaired. I have already made the Master MP standalone.

Whilst isolating the Master MP electrically via an external switch and switching it off, I can’t seem to connect with the Slave in VE Configure. Is there a process documented to delete the master and reconfigure the slave as the master standalone.

That way at least I can get 230V back on the boat.

15

Make sure your mk3 and Cerbo aren’t connected simultaneously.
If all else fails use veflash to reimage the units individually.

16

I have the system back with the Master MP in standalone mode. I wasn’t able to reflash the Slave as I don’t have a professional account and thus can’t download the firmware. I did however manage to fluke access (10 tries) with the configurator and reset it to default as I had the Master. It came online dropping the Master off obviously with no error leds. I noticed however the In frequency was 47.8 Hz as opposed to the master consistently previously 50.1Hz.

SlaveResetNote Freq040326_2
SlaveResetNote Freq040326_21774×984 336 KB

When I then tried to parallel them I got a not in phase message on VE monitor. Clue was there earlier as above but I didn’t twig.

Master Not in phase
Master Not in phase1645×829 222 KB

Soon after the Master dropped off black and tripped the shore breaker.

I reverted to the Master in standalone and all is fine albeit with limit KW availability.

Lesson for me on this was to get into VE configure earlier, reset to default configs and see what happens then before pulling panels and wires and wasting time in yoga contortions with less than zen like composure by the end.

I will RMA the Slave MP and see where I go from there. Thanks for your input.

17

Anyone can have a professional account. It’s free.

18

Sometimes happens when there is a bit of feedback from one to the other.in the wiring.
Does it do it with no wiring attached at all?