ProMariner 70A 2-Alternator 2-Battery Isolator

The ProMariner 70A Battery Isolator handles two alternators charging two separate banks, with gold-plated terminals.

Seventy amps is the smaller rating in this range, against the 130A version of the same configuration. Matching the isolator to the alternators rather than the batteries is the calculation: an isolator rated below the combined alternator output becomes the limit and heats under load.

That heat is the failure mode rather than an outright trip, and it develops slowly enough to go unnoticed. Sizing generously costs little compared with replacing a cooked isolator and whatever it took with it.

Two alternators into two banks keeps each charging source and bank on its own path while both stay electrically separate. Gold-plated terminals support reliable high-current connections in the damp, salty conditions of an engine space. Explore more battery isolators and charging relays.

• 70A, against the 130A version of the same layout
• Match the isolator to the alternators, not the batteries
• Undersized, it becomes the limit and heats
• That heat develops slowly enough to go unnoticed