question

Balancers with batteries in parallel are completely worthless. Balancers work by moving charge from higher voltage to lower voltage... when batteries are in parallel, they are at the same voltage.

Multiple batteries in parallel suffer from increasingly uneven current as the numbers increase. Many have done six and many have done many more.

Connecting parallel batteries via bus bar generally results in the best balance among batteries.

Google "Victron Wiring Unlimited" and read it for the paralleling options.

As @snoobler mentioned, you should use a busbar for the batteries. Be aware, that ALL PLUS cables need to be the same lenght and ALL MINUS cable need to be the same lenght otherwise you create a different voltage drop on each cable. Make the busbar as voluminous as possible. My new Busbar is from Aluminium and has 15x80mm and i connect 3 MultiPlus-II 24/5000 (i use them in parallel) between each two battery connections to get the best balance between the Batteriesband the Inverters.

However, it is not easy to use Aluminium as Busbar, because youvhavevto use A2 bolts, Washer and Nuts as well as you need to treat the surface (because of the heavy oxydation) and use a huge amount of polfat (e.G. ENSTO).

For non experienced users better get some cut-offs from a coper bar, e.G. 10x50mm and a lenght of 200mm. Which should be definitively enough for your 6 or maybe 8 Batteries. You can even remove the Shunt of the SmartMeter/BMV from the plastic base and bolt it directly on the Busbar which I have done too...

You will find a better explanation in the Victron Book "Wireing Unlimited"

When you add the batteries, make sure all are at the same voltage. Otherwise there will be some unwanted sparks/heavy currents.