Hi I have a Victron ecosystem MultiPlus Inverter, RS485 Charge Controller and a CebroGSX, connected via the Lynx buzz bar. I have two 11KwH LiFePO batteries of the Chinese Rosen brand. I have upgraded the BMS of both batteries to the JKBMS as the original BMS’ were problematic. Since the upgrade things were fine for a while.
Just recently I have noticed that one of the two batteries, drains completely while the other remains full.
There are no physical fuses nor breakers blown, and I can not find any settings in either the Victron nor the JKBMS that would cause this.
The only recent settings changes I have made was to my ESS assistant in the Inverter (as I push and pull power from the grid at times), as I had the dynamic shut off set too high which was throwing low battery alarms and shutting things down. Since amending those settings the batteries were reaching both ends of their empty and full levels. until one started reaching completely empty before the other starts discharging.
Has anyone seen this before? can you advise what would cause this behaviour.
Ok The batteries have individual cables which are the same length. these go to individual 250AMP DC Breakers. from there I have same length cables terminating onto a Victron Lynx buzzbar.
Both batteries are exactly the same size. In the JKBMS the bottom battery is set as the master and the top battery is a slave. the Victron CAN is to the Master battery with battery to battery coms via the RS485 connections.
I’ll do this tomorrow when the wife is at work. But as the BMS shows stats in the Victron as 400A instead of 200A and the cell high and low stats are present in the Victron platform. And I can Bluetooth to each battery individually via the JKBMS app, and see the cells and total capacity (which is why I know that one is full and one is empty). I do not think this is true.
So then there is a physical problem that has developed. Loose or dodgy connection affecting resistance to one battery.
Most likely suspect an oxide build up in the dc breakers. (Other than checking all lug torques)
Switch off the system including batteries, cycle them on and off a few times. (Maybe swap over connections to eliminate them as an issue?).
That sound on the inverter sounds like a core saturation and collapse. Can be a number of things that cause that. Most point to a DC power supply problem. Either batteries or power pack. (Internet diagnosis being what it is)
Ok I isolated the slave battery. By turning it off and disconnecting its quick release terminals (see photo Mater bat only). I also disconnected the solar panels and turned off the Charge controller. I still had power to the house with no issues. So that rules out the Master battery being dead.
I have also made a second recording of the inverter with only the Master battery connected, and there is no pulsing sound now, even after both batteries are connected. (see video)
The Slave battery is clearly being drained well before the Master see the Battery BMS stats from the JKBMS screen on the battery, and the Victron VRM stats first with just the Master Bat then both Bats.
Next test will be to swap the cables going to the DC breaker switches and determine if this inverts the issue. If is does then I agree, there is a cable or DC Breaker issue. Otherwise I am at a loss. All terminals where made using a Hydraulic crimper to the correct spec. and All terminals have been torqued to the Victron Nm.
Ok I think I found the issue (I hope). When moving these quick connect battery terminals around I found that after they click meaning that they are locked, there is still a 1mm of movement you can push them into the socket. So I suspect when I had my batteries out previously I did not seat one or more of the cables on the Master battery correctly, and while a connection had been made it was not correct and thus the suspected resistance difference between the two batteries occurred.
In my attempt to invert the issue I unplugged all 4 of these quick connect plugs and then swapped the slave cables to the master battery and the master cables to the slave battery. It was during this process I discovered that clicking does not mean seated, so firmly pushed all 4 plugs home into their respective receiving sockets.
I have made no other changes to the physical system. And since swapping the cables around, both batteries seems to be working in sync again. I needed to charge them to 100% and then wait a couple of hours for them to top Balance. but since then they appear to be draining and filling at a similar rate (not exact but very close).
So for now I am just watching and waiting for any signs of the previous issue. Further the weird sound the inverter was making has also not returned since swapping the cables around.
I’ll update you if the issue returns, but for now I think this issue is solved.
