Adding a 3rd Lithium battery

[Marine359]

Pardon me, $12 for 2ft 1/0 with ring terminals

[Phil G.]

Here's a link describing how to connect multiple 12V batteries together such that each battery gets fed current through paths of the same resistance as the others when being charged, and such that each battery supplies current through paths of the same resistance as the others when feeding loads -> this is called connecting batteries together in a "balanced" way:

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

[tinglett]

Awesome...that's the web page I couldn't find. Very much worth reading!