Battery Isolator 12V Kit 140Amp Split Charge Relay - Automatic Dual

Our review of the Battery Isolator 12V Kit 140Amp finds it best suited for owners who need a simple, rugged way to keep an auxiliary battery charged without risking the primary battery. The kit's automatic voltage sensing that cuts in at 13.3 volts and cuts out at 12.8 volts is the single biggest reason to consider it, since it protects the starter battery while allowing reliable charging of an auxiliary battery for marine, RV, ATV or overland use.

Key Features

• Silicone sealed housing: The durable, weather-resistant case helps the relay survive damp or salty environments common on boats and offroad vehicles.
• Voltage sensitive switching: The relay automatically connects and disconnects based on charging voltage, ensuring the primary battery stays charged for engine starts.
• 140 amp capacity: The high current rating supports most dual-battery setups for medium sized vehicles and marine systems without frequent overheating.
• LED indicator: A front panel LED gives a quick visual of when the relay is engaged so users can confirm charging status at a glance.
• Complete wiring kit: Included 20 ft 6AWG cable and installation hardware simplify mounting and wiring in tight engine bays or battery compartments.

Who It's For

This kit suits boaters, RV owners, overlanders and anyone who runs accessories from an auxiliary battery and wants an automatic way to keep it charged without touching the ignition or alternator wiring. The compact relay and long 20 ft cable make it handy where space is limited.

It is less appropriate for systems that need programmable charge profiles, smart isolation features beyond voltage sensing, or integration with battery management systems; those users should look at multi-stage charging or DC-DC charger solutions.

Pros & Cons

Pros

• Easy to install with the supplied 6AWG cable and hardware, which many customers praised for simplicity.
• Protects the primary battery with clear voltage cut-in and cut-out thresholds so the starter battery remains ready.
• Sturdy, sealed construction that stands up to marine and offroad conditions.

Cons

• Some users reported mixed functionality in a few cases, so results may vary depending on system and installation.

Specifications

Our Verdict

The Battery Isolator 12V Kit 140Amp is a practical, value-oriented choice for users who need a rugged automatic relay to maintain an auxiliary battery without risking their starter battery. Its clear voltage sensing, LED status, and included 20 ft 6AWG wiring make installation straightforward and reliable for typical automotive, marine and recreational use.

Frequently Asked Questions

Does the relay require alternator or ignition wiring?
No. The unit is voltage sensitive and does not require a separate alternator or ignition connection to operate.

Will it work in a marine environment?
Yes. The silicone sealed interior and sturdy housing are designed to withstand harsh weather and marine conditions.

What happens if the relay does not engage?
If the relay does not engage customers report mixed results; verify installation, cable connections and battery voltages before contacting support.