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A 12V, 140A smart battery isolator that sits between two batteries on a common ground and connects them only when a charging source is present. It is dual-sensing, so a charge on either battery engages the relay and charges both, and it waits until the first battery reaches 13.4V before linking the second. Unlike diode isolators it has no voltage drop and needs only three wires at the battery, with no alternator rewiring. It suits van, boat and off-grid owners with a starter and house battery who want automatic charging without a manual switch.
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Owners of dual-battery vans and boats rate these isolators for simple wiring and charging both batteries from either side. The main complaints are the audible relay click and the fixed voltage thresholds, which some find high for lithium.
This smart battery isolator is a 12V relay that automatically separates and connects two batteries that share a common ground. It lets both batteries charge from one source and keeps them isolated when no charging source is present. This prevents the start battery from being drained and protects sensitive electronics powered from the house battery.
The isolator is dual sensing. It reads the charge of both batteries, so if either one is receiving a charge, such as a charger connected to the auxiliary battery, the relay engages and charges both. It makes sure the first battery reaches 13.4V before connecting the second. This avoids problems when the charging source is too low in amps to charge all batteries at once.
When the engine starts and the start battery reaches 13.4 volts, the relay engages and charges the start and accessory banks together. When the voltage drops below 12.9 volts, for example when the engine stops, the relay disengages and separates the batteries. Units can be placed in sequence between batteries to charge several in a multiple-battery setup, such as a larger boat with 2 or more house batteries.
