EnerSys, the inventors of the Odyssey TPPL AGM battery as well as the inventors of the Optima battery, and the leaders in standby back up systems, military applications and other industrial battery applications spells out correct parallel wiring better than I can. When you are wiring series banks in parallel this applies!


Quote = Odyssey/Enersys:


"Parallel Connections


It is common to have batteries connected in parallel to
achieve a desired amp-hour capacity. This is done by
connecting all the positives to each other and all the
negatives to each other.


Typically the positive and negative leads to the load
are taken from the same battery; usually the leads from
the first battery are used. This is not a good practice.
Instead, a better technique to connect the load is to take
the positive lead from one end of the pack (the first or last
battery) and the negative lead from the other end of the pack.
The two methods are illustrated above. Solid lines and
arrows indicate positive terminals and leads; broken lines
and arrows indicate negative terminals and leads.


In both illustrations, the positive leads are connected to
each other; similarly the negative leads are connected to
each other. The only difference is that in the first illustration
the positive and negative leads to the load come from the
first and last batteries. In the second case, both leads to
the load are tapped from the same battery.


The first schematic is recommended whenever batteries
are hooked up in parallel to increase battery capacity.
With this wiring, all batteries are forced to share both charge
and discharge currents. In contrast, a closer inspection
of the second schematic shows that it is possible for only
the battery whose terminals are tapped to support the load.
Implementing the first schematic eliminates this possibility
and is therefore a better one."