Ok, I’ve been able to figure out and address most of the “previous Owner” changes but this one still has me baffled. A PO had a damn nice JL Audio stereo installed and was clearly professionally done complete with two 5ch amps, subs, and two very expensive Stinger AGM batteries cleanly wired (and fused) in parallel as its own bank so as not to pull down the others. Here’s the puzzler that I’m hoping the electricians here can explain. They ran very heavy gauge Pos and Neg cables from the Stinger batteries to the engine room to charge off the main charger (and I’m guessing alternators) but ran the Neg cable to the Neg terminal on the House battery and the Pos cable (fused at the battery) to the Pos terminal on the Port starter battery. You can see the cable and fuse in second pic. Why the split across the two charging banks/batts? I hope my drawing illustrates what I’m describing. And for additional info, the main charger is a 3 bank with 1 each to the 2 starting and 1 house batteries. Genny has its own.