3 banks of 3 100ah 12v batteries

[JAYFEATHERBOONDOCKS]

Hello ?? I would like to build three banks of three 100 ah 12v batteries in my camper for the summer months and running a/c while boondocking. I currently have 3 SOK 100ah 12v n/heat n/bluetooth and I would like to add 6 more 100 ah cheap batteries such as redodo or power queen to save money. In order to do this I would create three banks of three and run equal distance cables to a 4 post buss bar and run the inverter to the buss bar with proper fusing in between each bank and also running the solar charge controllers to this buss bar. The two banks of cheap batteries will be moved out of the camper before winter and used indoors as power backup for deep freeze and furnace if power goes out. Is this an absolute no do not do or is it okay for weekend boondocking use?

Should I consider an A/B switch and only have two banks bank A being the three SOK’s and bank B being the 600ah cheap batteries?

Let me know what you all think good and bad. Picture is very basic just to help convey the idea it does not show any safety features I was pressed for time.

 

[sunshine_eggo]

Note that on each parallel group of three, you must connect the main leads "across" the battery, so that one is on battery #1 and the other one battery #3. If you connect them as you depicted, the first battery in each chain will bear the brunt of the demand.



Wire gauges need to be the same. The sum of the (+) and (-) wire length to each group of 3 must be the same. It's okay if the (+) and (-) are all different, but (+) + (-) must be the same for each group of three.

No selector switch.

 

[jberger]

The fewer batteries you connect, the less balancing issues you should have.
I would not look to add multiple banks for (3), just buy larger amp hour batteries. ie, buy (2) 400 ah instead of (6) 100ah.
Going with bigger ah packs really simplifies the number of connections, BMS limitations and balancing issues.
When you start connecting multiple batteries, you also have to contend with the BMS limitations of the worst/smallest BMS. Those cheap 100ah might only be able to support a limited amperage draw or only (4) connected batteries. So as you add them, you magnify any underlying limitations.