one BMS taking more load in a multi battery bank setup

I currently have 3 (48v 304ah battery banks), each with their own bms (2 JK bms units and 1 with a jiabaida bms).
What i am finding is my battery bank with the jiabaida bms is basically controlling everything.
If that bank runs out of energy the entire system shuts down.
I have checked the other 2 JK BMS units and they both say 60% SOC and voltage is anywhere between 51-52V.
There is some current flowing out between 5-10amps but nowhere near the 20ams the jiabaida bms takes.
If i shut down the jiabaida bms then the JK units take all the load, but if i turn it back on, 90% of the load goes back to this unit.

All 3 battery banks are running to a breaker, then wired to a main bus bar. From the main bus bar i have 2 connections going to 2 different inverters.

Is there anyway to get this balanced so that all 3 banks are distributing the load evenly?
I dont have Rs485 or canbus connected as my growatt units dont seem to be working with them.
I did buy a victron smart shunt but i havent set that unit up yet.
Any chance there is a incorrect setting in the BMS that could be causing this one battery bank to act like a "master" bank?

Any advice would be great!
Thanks

terrango said:

If that bank runs out of energy the entire system shuts down.

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Is this by design? Sounds odd. Happen to have a pic of your wiring?

terrango said:

All 3 battery banks are running to a breaker, then wired to a main bus bar

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The preferred safety method would be a class T fuse at each battery, before combining.

terrango said:

Is there anyway to get this balanced so that all 3 banks are distributing the load evenly?

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Your description sounds reasonable in terms of balance. Cannot understand how/why one would work as a "master" battery for the entire bank.

A pic and a description will help the group diagnose this.

You state that all 3 battery PACKS are identical 16S/304AH and you have 1 JBD & 2 JK BMS'.
If the settings are as closely matched in the BMS' as possible, there should be little to no difference. IF these had been different sized battery packs then it would not be out of place as they discharge proportionately to capacity, with the bigger packs discharging more than smaller ones.

You are running a Common DC Bus (making the 3 batteries into One Bank of Batteries) and driving 2 Inverters from that common DC BUS which is perfectly fine. Your description of Breaker Setup leaves me wondering...
You can have a Fuse or Breaker between each battery pack and the common DC Busbar, Then a Breaker between Common DC Bus & Target Inverter, so 2 breakers, 1 for each Inverter. There should also be a Breaker between the Solar Charge Controller & Main DC Bus IF you are using NON-AIO Inverter/Chargers. IF using AIO's that's shared through the common line from the AIO Unit, so you have to be sure you are using the correct type of Breaker that is Bi-Directional.

Balance is not difficult, starts with very basic things like Equal Wire Gauge for all batteries from Pack terminals to bus bars and that includes Length of wire. You also have to account for the LOSSES for the wire but also any Fuse/Breaker in the circuit path... Every item in the circuit will add to the collective losses and yes, breakers, fuses, terminal lugs etc all add to it.

First QUICKY you can do, is to compare the settings between BMS' and try to match them up as closely as possible and see if that makes any difference. If you have different capacity BMS' that may also be a factor... ie if both JK's are 200A and the JBD is 150A that may make some difference, but that should be minimal as you are operating below maximums...

I will make a photo later today.
Just want to clarify the breaker is not a combining all 3 banks.
The pos and neg of each bank is wired to a DC breaker then the 3 pos/neg leads go to the corresponding + - bus bars.

All 3 banks are listed as 310ah cells, but i have them set in the bms as 304.
I havent touched most of the settings in the bms units.
They are pretty much factory with exception of the basic settings.

The original design was to have all 3 banks work together.
All 3 BMS units are 200a bms.
Would it be worth while to change all BMS units to the same style?
The 2 JK bms units seem to work in tandem together normal.

I am building a new battery shelf similar to Andy's from Off grid garage (another 1-2 months to complete depending on time).
In the short term i wanted to sort of real world test these cells and BMS units to ensure they all work before relocating.
I didnt want to spend all the time relocating and setting everything up and find out there is problems.
But ill make some photos and see if there is anything that stands out.

terrango said:

The 2 JK bms units seem to work in tandem together normal.

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This sounds odd. The BMSs are pretty much just cutoff switches and should operate independently. In fact, the BMSs should have no idea about or care that there are other BMSs.

That being said, your 3 batteries will likely behave better if the settings in your 3 BMSs are identical. I would REALLY look at the default settings and make sure they are identical.

Is the wire used for each bank the same brand, size and length from each terminal to the busbar?

Are all the lug types the same brand/type/material and torqued to the same values?

When you are combining AR the busbar, did you stagger the + and - connections opposite each other? If you have one bank with both + and - leads closest to the inverters, that can drive favoritism.

Example of 3 battery banks and 1 inverter on two 4 post busbars

Not Ideal:
+bus -> BB1 BB2 BB3 INV
-bus -> BB1 BB2 BB3 INV
This would place battery bank 3 (BB3) as the primary power supply

More Ideal:
+bus -> BB1 BB2 BB3 INV
-bus -> BB3 BB2 BB1 INV

I check the BMS settings later also.
I believe all the wiring from the batteries to the inverters is all 2ga now.
Some connections have bigger lugs as i couldnt get the correct size at the time.
Not sure if using a stainless washers, bolts and nuts make a difference.
I do intend to switch to the proper lugs when i move everything over to the new battery shelf.

PreppenWolf you make an interesting point on the busbars.
If i recall i do not have the wires arranged in an ideal fashion..
something to fix.

Tell is if the Jia has shorter cables than the other two banks?

Anything that causes the two JKs to have higher resistance will disfavor them from being equal share of supply.

Current flow takes the path of least resistance .... You will need to find out why that pack or it's associated wiring has less resistance than the others.
That may involve swapping the BMS that is different from the others with one of the other packs to see if that is the reason ... other possibilities are in posts by others.

update: this JBA bms is no longer working. The BMS locked itself in protection mode and wouldnt release even though the battery was fully charged. So i am going to swap it with the same style JK BMS and see if it works better. lol i was thinking of taking a photo last night of the system, but i have cables everywhere as i had to do some surgical work to bypass things before things got too cold in my solar shed.
Once i swap the BMS and fix the cables ill post a photo.