KeyLine Chargers Dual Battery Isolator Kit 300A VSR, 1000A Peak — 12V IP65, LiFePO4 & Lead‑Acid Compatible

The KeyLine Chargers Heavy Duty 300 AMP Dual Battery Isolator Kit is a compact, IP65-rated Voltage Sensitive Relay (VSR) system that automatically manages charging between two 12V batteries — including lithium and LiFePO4 — and delivers up to 1000 AMP peak for high-demand setups.

This complete kit combines a robust 300A continuous VSR with the cables, terminals and fittings needed for a tidy install, designed for vehicles and mobile power systems that require more than standard isolators can supply. The relay engages at 13.3 volts and disengages at 12.8 volts to protect your starter battery while allowing heavy auxiliary loads to charge when alternator voltage is high. Built for rough environments and large battery banks, the KeyLine 300A isolator targets off-road, marine, RV and commercial uses where uptime and reliability matter.

How does this isolator protect my starter battery while charging large auxiliary banks?

The KeyLine VSR monitors system voltage, connecting the auxiliary battery only when alternator output reaches a safe charging threshold and disconnecting before starter battery voltage drops. This preserves starting capacity while enabling high-current charging for accessories and inverters when appropriate.

• Engages at 13.3 V and disengages at 12.8 V to prioritize start battery health.
• Zero-drop VSR design avoids the amperage loss common to diode-based isolators.
• Handles 300A continuous with 1000A peak for heavy loads and cranking events.
• Works with lead-acid, AGM, gel, lithium and LiFePO4 chemistries.

What’s included in the kit and how does it simplify installation?

The package supplies the isolator plus all major electrical components so you don’t need to hunt for parts. Cables, terminals, crimps and heat-shrink arrive ready to mount, reducing install time and ensuring components match the isolator’s current rating.

• Smart 300A VSR with mounting screws for secure placement under the hood or in a protected compartment.
• 1 AWG red 20' positive cable and 1 AWG black 2' ground cable sized for high current.
• Marine-grade positive and negative battery terminals, copper crimp lugs, insulated ring terminal and heat-shrink tubing.
• Zip ties and simple hardware to route and secure cables neatly.

Is this unit durable enough for off-road, marine, or heavy commercial use?

Yes — the KeyLine 300A isolator is IP65 certified for dust and water resistance, built in a compact housing that fits tight engine bays while surviving harsh conditions. The robust construction and high-current components make it suitable for sustained high loads and exposure to vibration and weather.

• IP65 rating protects against dust ingress and water jets — suited for wet, dusty environments.
• Compact footprint allows installation close to battery banks or under the hood.
• Thermally managed components and quality crimps for long-term reliability.

Will this isolator work with modern lithium and LiFePO4 battery systems?

The VSR is compatible with lithium and LiFePO4 when used with battery-management best practices. It connects based on system voltage rather than battery chemistry, letting you pair it with appropriate battery-specific chargers or BMS settings for optimal charging behavior.

• Voltage-triggered switching is chemistry-agnostic; works with lithium and LiFePO4 banks.
• Recommended to use alongside a BMS or dedicated lithium charger for charge profile control.
• Zero-voltage-drop topology maximizes available current for fast charging of high-capacity banks.

Who is this for: The KeyLine Chargers 300 AMP Heavy Duty Dual Battery Isolator Kit is aimed at users who run large auxiliary battery arrays or high-draw accessories — overland rigs, RVs with inverter systems, commercial vehicles, marine craft and anyone upgrading beyond standard isolator capacities. If you need a compact, weather-resistant VSR that supplies high continuous current, includes installation hardware, and supports modern battery chemistries, this kit is tailored to those demands. Every unit ships with a three-year warranty and a 30-day money-back guarantee for added confidence.