To join batteries in parallel, use a jumper wire to connect both the positive terminals, and another jumper wire to connect both the negative terminals of both batteries to each other. Negative to negative and positive to positive. You CAN connect your load to ONE of the batteries, and it will drain both equally.
By connecting batteries in series or parallel or series/parallel you can achieve the correct. Other important points to bear in mind when wiring boats or RV's:.
If you're wondering why your batteries in parallel fail sooner than they should, read our blog on how to charge batteries in parallel for a balanced charge.
Most marine batteries onboard boats today are of the lead-acid type.. . the marina talk about connecting batteries in series and connecting batteries in parallel.
Series and Parallel Battery Packs; Series Connections; Parallel Connections; Series/ Parallel Connections; Connecting Battery Chargers to Series and Parallel