STINGER SGP35 12V High-Current Battery Relay & Isolator — 500A Continuous, Water-Resistant for Marine & Car Audio

The STINGER SGP35 is a water-resistant 12V high-current battery relay and isolator that safely combines charging while isolating batteries, rated for 500A continuous with 900A surge capacity.

Designed for automotive, marine and powersports systems, the SGP35 provides a robust way to add a secondary battery or protect a primary battery from accessory drain. Built from phenolic plastic to resist moisture and corrosion, this relay switches with your ignition to allow charging while keeping battery circuits separate when the engine is off. Its long mechanical life and high current limits make it suitable for high-demand car audio, winches, auxiliary lighting and off-grid accessory setups.

How does the SGP35 prevent my primary battery from draining?

The SGP35 acts as an automatic isolator: it closes only when the ignition is on, linking the starter battery and auxiliary battery for charging. When the engine is off, the relay opens to leave batteries electrically separate, preventing accessory load from drawing down the starter battery.

• Automatic ignition-activated switching for hands-free operation
• Isolates batteries when ignition is off to protect starter power
• Compatible with simple trigger wiring—no complex control modules required

Will this relay handle high-current car audio or winch loads?

Yes—the SGP35 is engineered for demanding loads. It supports continuous currents up to 500 amps and tolerates short surge events up to 900 amps, giving headroom for powerful amplifiers, winches and heavy-duty accessories.

• 500A continuous rating for sustained accessory draw
• 900A surge handling for brief inrush currents from amplifiers or motors
• Solid contact construction for efficient high-current transfer

Is the SGP35 suitable for marine and off-road use?

Yes—the housing is made from water-resistant phenolic plastic to resist moisture and corrosion common in marine and powersports environments. Its sealed design and durable construction make it a reliable choice for exposed installations.

• Water-resistant body protects internal contacts from humidity and spray
• Robust build rated for 100,000 mechanical cycles for long service life
• Works with all 12V alternator and charging system types

How do I install and wire the SGP35 with my alternator and batteries?

Installation is straightforward: mount the relay in a dry, accessible location, run heavy gauge battery cables to the main contact studs, and connect an ignition-switched trigger wire to activate the coil. Use appropriately sized wiring and fusing for the current you expect to carry.

• Mount on a solid surface with adequate ventilation and access
• Use heavy-gauge battery cables and proper ANL or inline fuses
• Connect a switched 12V trigger to operate the relay with ignition

Who is this for? The STINGER SGP35 is made for vehicle owners and installers who need dependable battery isolation and high-current capability: car audio enthusiasts running big amplifiers, boat owners protecting starter batteries, off-roaders using winches and accessory banks, and anyone adding a secondary battery to a 12V charging system. It’s especially useful where moisture resistance and long mechanical life are required, and for systems that demand quick, automatic switching without complex electronics.