Wiring components side-by-side so their currents add while voltage stays the same. Parallel batteries should share equal-length, equal-gauge leads so they work evenly.
Parallel wiring adds current while voltage stays the same — but current takes the path of least resistance, so unequal leads make one battery do more work, run hotter and age faster.
Batteries in parallel must share equal-length, equal-gauge leads to the busbars so they charge and discharge evenly and the bank stays balanced.
Design your van, boat, cabin or RV system in Wattonomy and it flags parallel banks and calls for equal-length, equal-gauge leads so the batteries share load evenly — from the appliances you actually run, sized to the recognized standard for your region. You see it on the wiring diagram, in the sized parts list, and in a plain-English build pack that explains the reasoning behind every choice. No account, no email — about a minute to a complete, validated design.
Because current follows the path of least resistance. Shorter leads make one battery work harder and age first; equal leads share the load evenly.
Use identical, equal-length cables to a common busbar (or diagonal takeoffs), and charge all batteries to the same voltage before first paralleling them.
It takes about a minute. No account, no email.