Stinger SGP35 500-AMP Relay and Isolator - Heavy Duty Battery Control

In this review of the Stinger SGP35 500-AMP Relay and Isolator, the bottom line is simple: this is a heavy-duty, no-frills relay for anyone adding a secondary battery to a 12 volt system who needs reliable high-current switching. The reviewer found it especially useful for commercial truck installs and car audio systems because it prevents the primary battery from discharging when the engine is off while still allowing full charge back to auxiliary batteries when the ignition is on. It is built to last and performs its core task without unnecessary complications.

Key Features

• 500 AMP contact rating: Handles high current draws common in large audio systems and commercial vehicle setups without noticeable voltage drop.
• Prevents primary battery discharge: Keeps the starter battery isolated when the ignition is off so electronics or accessories do not drain the main battery.
• Power on demand: Automatically connects batteries when the ignition is turned on, providing charging to auxiliary batteries only when appropriate.
• Water resistant phenolic housing: Durable black phenolic plastic helps protect the relay in damp engine bays or exposed installations.
• Universal 12 volt compatibility: Works with a wide range of alternators and charging systems, simplifying integration into most vehicles.

Who It's For

This relay is aimed at vehicle owners and installers who need a high-current, dependable solution to add and manage secondary batteries in cars, trucks, RVs and commercial vehicles. It is a good fit for car audio enthusiasts who run large amplifiers, fleet technicians who outfit trucks with auxiliary systems, and anyone who wants straightforward battery isolation without smart electronics.

Those who want integrated battery sensing, timed disconnects or multi-stage charging intelligence should look elsewhere; the SGP35 is a robust mechanical relay/isolator focused on high current handling and reliability rather than advanced battery management features.

Pros & Cons

Pros

• High 500 AMP rating supports heavy amplifier loads and large auxiliary battery charging.
• Water resistant phenolic case improves durability in exposed locations.
• Simple wiring and reliable operation make installation quick for installers and DIY users.

Cons

• It is a purely mechanical relay without advanced charging control or smart sensing features.

Specifications

Our Verdict

The Stinger SGP35 is a reliable, high-current relay ideal for anyone who needs straightforward battery isolation and robust amperage handling. Its durable construction and simple operation deliver strong value for car audio installs and commercial vehicle battery systems, while buyers seeking intelligent charging features should consider a different product.

Frequently Asked Questions

Will this relay work with my vehicle alternator?
Yes, the SGP35 is compatible with all types of alternators and charging systems in 12 volt vehicles.

Does it prevent the starter battery from draining?
Yes, the relay keeps the primary battery isolated when the ignition is off to prevent discharge from accessories.

Is it weather resistant for engine bay mounting?
Its water resistant black phenolic plastic housing helps protect the relay in damp or exposed installations.