Help with paralleled batteries

[Pr4mr22]

I was actually running a fan, and the refrigerator and later ran the AirCon with both batteries connected and no shore power attached.  It showed the battery voltage and amp draw (-18 amps), but says it's resting and gives a zero reading for the rest.  Unfortunately I don't have a way to display individual cell health and after resetting the BMS there are no faults. 

I did find this after dinner. It shows cell voltage min and max.

Of course, this is with only the back battery connected to coms. I am not using a link cable currently connecting the 2 batteries comm ports. 

Everything seems to work fune open loop.

[ClassicCrazy]

I wrote a long reply but lost it when I went to make my screen capture.
What you explain is having one battery in closed loop -canbus to the charger ( Rosie or HB ? ) and then the other battery in parallel with that but no link or communication with the first battery.
That probably isn't the best way to do it for charging . You would be better off with them both not connected to the charger via canbus  and have them both open loop ( no communication to the charger).
What  you first described sounded like a cell imbalance issue when it went to OVP warning. It is too hard to determine exactly what was going on when there isn't monitoring software to be able to look into the bms and see all cells voltages, current, balancing, alarms, etc.
Having some cell imbalance isn't uncommon and if you follow the manufacturers recommendations for charging , then the bms over time should be able to balance them back .
I am lucky that I have monitoring that will not only look at the live data , but also graph what is going on.
In the example below you see that one of my batteries has cells that were very closely selected and balanced from day one and all charge very close together as they come up to 100% SOC and hit absorb voltage. The second battery has some cells that are not so well selected and they show some very weird behavior on charging . But since I added in an active balancer to this , it straightens they out when in absorb.
It took me quite awhile and some study to really understand how these LiFePO4 cells and batteries function at their best. Watching Off Grid Garage videos on youtube helped because Andy there takes the time to test, graph , and then explain the resulting graphs with voltage, current relationships.
Of course if you just follow Midnite recommendations for charging that should do okay for you.
Larry 

[holdmode]

The problem - when I connect the battery's BMS via ethernet to each other, all the lights on the 2nd battery placed in the back, including the ALM Red led, start blinking. The batteries were balanced to 54.33v exactly prior to connecting them together.

Also, when I connect the canbus to the Rosie Inverter, the MNGP2 only reads 100ah of battery when it should read 200ah.  The MNGP2 also isn't giving me any AC readings, if that's important, but the Rosie is inverting as I have 120AC inside the rig. Both the Rosie and MNGP2 have updated firmware as of last week.

My guess - Bad BMS?.. in brand new battery?

Basics of the set-up incase it helps.  2440 watt Array on roof in 2s3p configuration running to Victron 150/45 SCC - 60amp fuse on the positive cable from the SCC connected to the back battery positive terminal.  Negative cable connected to the front battery negative terminal from the SCC to ensure better balanced charging.  Positive cable out to the Rosie is connected from the front battery with T-class 350A fuse in line and the Negative cable is connected from the back battery.   

I have a Lynx Distributor but didn't think it necessary for this build.  Could the charging and output configuration be an issue?  Would a busbar solve the problem?  My research says no, but...

I left a message with Midnite Power, but have not heard back.  Last time they didn't call back.  I had to reach out to them a second time.

Any help appreciated.

Pete

I don't like your configuration, I seen many postings about 100 amp lol "including me", and battery problem's, "Switch your setup", go back to the user manual page 11. link out to link in, and Can/485 to Rosie." "ALM Red led, start blinking", bad connections

[FNG]

Just to confirm, You start with BOTH batteries OFF not just the breaker but the power button as well?

With them off you run from Link IN on one to LINK OUT on the other?
With them off you run from the CAN/INV port on the battery with nothing plugged into its LINK IN port?
Then you switch the batteries on and get a cell over voltage alarm?

If so I would concur it sounds like a fault with the battery. Rosie is just telling you the alarm is present. That said cell over voltage can happen some times when charging. I would disable all chargers and load the battery to draw it down to say 75% and see if the error goes away?

No RED LED on either battery?

[Brucey]

Just to confirm, You start with BOTH batteries OFF not just the breaker but the power button as well?

With them off you run from Link IN on one to LINK OUT on the other?
With them off you run from the CAN/INV port on the battery with nothing plugged into its LINK IN port?
Then you switch the batteries on and get a cell over voltage alarm?

If so I would concur it sounds like a fault with the battery. Rosie is just telling you the alarm is present. That said cell over voltage can happen some times when charging. I would disable all chargers and load the battery to draw it down to say 75% and see if the error goes away?

No RED LED on either battery?

I'm pretty sure my Rosie lights didnt work when it was jumpered into quiet mode.