4 BSL 6.4kw batteries connected to Quattro 8000. Been working well for 4 months. Suddenly voltage dropped to 58% on colour controller and stayed there. removed the lan cables connecting batteries and then reconnected. This caused colour controller to show 100% charge but only shows 2 batteries online. I switched cables around but no change.
GX's will only show what the BMS is sending, so check all the comms cabling between the batteries.
The details tab of the BMS on the GX should also report how many modules are Blocking or not.
If it shows online but blocking then it isn't a comms issue.
Since you have done some of the above, this is something best addressed with your battery supplier, the GX has no control over what the BMS sends to it nor if modules decide to go offline
It is also worth confirming your setup is right, https://www.victronenergy.com/live/battery_compatibility:bsl
(double check all settings and dip switches on the batteries)
The Pace BMS used in these batteries (and some others) have had a few issues.
What do you mean by voltage dropped to 58%? Do you mean SOC?
Perhaps post some charts of of the BMS CVL, CCL and DCL as well as battery voltage/current during the issue.
Are all the LED's on the front of the batteries showing the same status?
