Keeping Parallel Bank balanced

[Pater C]

I have a bank of 3, 230ah batteries made of prismatic batteries (each battery has 4 cells). The cells within the battery are staying balanced, but one of the three batteries is now staying about 20% out of balance with the other two. I have the batteries wired in parallel to buss bars. In the picture you can see the green negative wires going to a buss bar in the back connected to a smart shunt. The red wires connect to the positive bus bar. All of the wires green negative wires are of the same length, and all of the red positive wires are of the same length. Is there anything I can or should do about this, or is having one battery out of balance the price of using a parallel bank of batteries?

 

[HRTKD]

Which battery is 20% low? Is it the one on the left? If so, move the big cable on post #1 (right most) to post #2 and the red cable on post #4 to post #1. Your bus bar is short enough that it shouldn't matter, but try it just in case.

How are the negative wires connected?

There should be a fuse (Class T recommended) on the positive cables coming from the battery.

 

[Pater C]

Which battery is 20% low? Is it the one on the left? If so, move the big cable on post #1 (right most) to post #2 and the red cable on post #4 to post #1. Your bus bar is short enough that it shouldn't matter, but try it just in case.

How are the negative wires connected?

There should be a fuse (Class T recommended) on the positive cables coming from the battery.

Thank you for your suggestion. I don't have access to my camper for the next couple of days, so I can't test yet which battery is low.

In the picture the big 4/0 cable goes to a Class T fuse and then to my inverter/charger. The negative wires (green in the picture) go to 4 post bus bar on the back, then to a smarthsunt, then to the negative busbar in the front of the picture.

 

[toms]

This is inevitable with parallel batteries, you will need to use a 12V charger to top them all to the same SOC periodically.
No need to disassemble the system, just remove the loads and individually charge the batteries.