Microprocessor-controlled dual battery isolator for RV, truck, and 4WD applications. Protects the start battery from excessive discharge while the auxiliary battery powers non-essential loads. 12V DC, 100A continuous.
The Redarc SBI12 is a microprocessor-controlled battery isolator that acts as a solenoid priority system in a dual battery setup. It keeps the vehicle's start battery protected from excessive discharge while allowing the auxiliary battery to supply non-essential loads, such as fridges, lighting, or accessories, whenever the vehicle is running. Rated for 12V DC at 100A continuous, the SBI12 is built for 4WD, RV, truck, and commercial vehicle applications where a dependable secondary battery charge is needed on the move.
Unlike a diode-type isolator, the SBI12 avoids the voltage drop that comes with diode isolation, and its electronic switching design prevents the solenoid from generating high voltage transients. An overmold design and silver contacts extend contact life, including in marine environments, while low standby current draw and onboard fault detection with LED indication flag issues such as voltage drops, over-voltage, or excessive current draw.
Protects the start battery from excessive discharge while the auxiliary battery supplies non-essential loads
Electronic switching design avoids the voltage drop and heat buildup associated with diode-type isolators
Fault detection with LED indication warns of voltage drops, over-voltage, or excessive current draw
Longer contact life and suitable for marine applications, in a compact, easy-to-install overmold housing
The SBI12 does not ship with fuses or fuse holders. A properly rated fuse kit is required on both the start-battery and auxiliary-battery cables for a safe, code-compliant installation. Redarc recommends its 100A Fuse Kit (FK100), sized to match the SBI12's 100A continuous rating. A 60A Fuse Kit (FK60) is available for lower-current installations using a different Smart Start isolator, but is undersized for this 100A unit. Running the SBI12 without correctly rated fuses on both battery legs is not a supported installation and can void warranty coverage in the event of a fault.
The SBI12 is one of several models in Redarc's Smart Start isolator lineup. Make sure you're ordering the right one for your charging setup: SBI12 (this product) - Single-sensing isolator; auxiliary battery is charged only by the vehicle's alternator while driving. SBI12D - Dual-sensing isolator; use this instead if the auxiliary battery may also be charged by an external source such as a solar panel or AC charger, since it allows that external charge to top up the start battery once the auxiliary battery reaches 13.2V. SBI12KIT - Bundles the SBI12 isolator together with the wiring needed for installation. Note: fuse kits (FK60, FK100) are sold separately from all of the above and are still required.
Determine how your auxiliary battery gets charged before choosing between the SBI12 and SBI12D: Alternator-Only Charging: If the auxiliary battery is charged solely by the vehicle's alternator while driving, the standard SBI12 is the correct choice. External Charging Sources: If the auxiliary battery is also charged by a solar panel, AC battery charger, or other external source while parked, choose the dual-sensing SBI12D instead so the start battery can also benefit from that external charge. Not sure? Check whether your setup includes a solar controller, inverter/charger, or shore power connection feeding the auxiliary battery bank.
Installation Steps (Professional Installation Recommended): 1. Confirm Your Charging Setup: Verify the SBI12 (alternator-only) is the right model for your auxiliary charging setup, versus the dual-sensing SBI12D 2. Purchase a Fuse Kit: Order a correctly rated fuse kit (Redarc FK100 recommended) sized to the SBI12's 100A rating 3. Choose a Mounting Location: Mount the isolator near the battery bank, in a location protected from direct water exposure 4. Wire the Start and Auxiliary Batteries: Connect according to the wiring diagram in the official Redarc install guide, fusing both battery legs 5. Secure All Connections: Ensure cable lugs and terminals are properly torqued to prevent resistance and heat buildup 6. Test the System: Confirm the isolator engages when the start battery reaches 13.2V and disengages at 12.7V, and check the fault LED for normal operation
In The Box: • Redarc SBI12 Smart Battery Isolator • Instruction manual • Install guide NOT Included (Must Purchase Separately): • Fuse Kit (FK100 recommended for this 100A unit) • Battery cabling and lugs • Mounting hardware
The SBI12's electronic switching avoids the voltage drop inherent to diode-type isolators, while its single-sensing design keeps things simple for setups where the auxiliary battery is charged only by the alternator. If an external charger or solar panel also feeds the auxiliary battery, the dual-sensing SBI12D is the better fit.
Download the SBI12 Instruction Manual Download the SBI12 Install Guide Download the SBI Range Brochure Technical Support: Redarc Technical Support Team Phone (United States): +1 (704) 247-5150 Phone (Canada): +1 (604) 260-5512 Warranty Information: 2-Year Limited Manufacturer's Warranty Covers defects in materials and workmanship under normal use Product Support Page: www.redarcelectronics.com