Description
Automatic dual-battery management protecting start battery while powering auxiliary loads
Product Overview
The Baintech Voltage Control Relay 12V/24V 100A is a fully automatic split charging relay engineered to manage dual-battery systems in 4WDs, caravans, motorhomes, boats, and commercial vehicles. This voltage-sensing relay intelligently prioritizes start battery charging before directing power to auxiliary battery banks, ensuring your vehicle always starts regardless of auxiliary load consumption. The relay remains open (off) until the start battery reaches preset voltage threshold, then automatically closes (on) to charge auxiliary batteries from the alternator. When the engine stops, the relay immediately opens (off), electrically isolating start and auxiliary batteries to prevent fridges, lights, inverters, or other auxiliary loads from draining the start battery overnight or during extended camping. Rated at 100A continuous current, this relay handles high-demand systems including large inverters, multiple fridges, and comprehensive camping electrical setups common to extended remote touring across Australia's outback regions.
Key Specifications
- Current rating: 100A continuous
- Voltage compatibility: 12V and 24V systems (auto-sensing)
- Operation: Automatic voltage-sensing split charging
- Relay type: High-current automotive relay with voltage control
- Activation: Preset voltage threshold on start battery triggers relay closure
- Deactivation: Ignition-off or voltage drop opens relay, isolating batteries
- Application: Dual-battery systems in 4WDs, caravans, motorhomes, boats, commercial vehicles
- Manufacturer: Baintech (Bainbridge Technologies)
- Made: Australian designed and engineered
- Protection: Prevents auxiliary loads draining start battery
- Mounting: Compact relay suitable for engine bay or battery compartment installation
Features & Benefits
Automatic voltage-sensing operation eliminates manual switching between batteries—relay monitors start battery voltage continuously, closing only when sufficient charge confirms the start battery is healthy, then directing alternator output to auxiliary bank without driver intervention or dashboard switches.
100A continuous current rating supports high-demand dual-battery systems including large pure sine wave inverters (1000W+), dual fridge setups, comprehensive LED lighting arrays, water pumps, and complete caravan electrical systems without voltage drop or relay overheating during extended charging cycles.
12V and 24V automatic compatibility serves both standard passenger 4WD/caravan applications (12V) and commercial truck/bus platforms (24V) without manual configuration—relay automatically detects system voltage and adjusts activation thresholds accordingly, simplifying installation across different vehicle types.
Start battery protection priority ensures auxiliary loads never compromise your ability to start the vehicle—relay keeps batteries isolated until alternator confirms start battery has reached healthy voltage, preventing the common failure mode where flat auxiliary batteries drag down the start battery through poorly-designed parallel systems.
Instant isolation on engine shutdown immediately opens relay contact when ignition switches off, creating complete electrical separation between start and auxiliary batteries—prevents fridges running overnight, inverter standby draw, or forgotten lights from slowly draining the start battery over multi-day camping periods.
Preset voltage activation threshold optimized for modern alternators and battery chemistry ensures start battery receives sufficient charge before auxiliary charging commences—eliminates risk of alternator overload or start battery undercharging that occurs with fixed-time delay relays not accounting for varying charging conditions.
High-current automotive relay construction with heavy-duty contacts rated for continuous 100A draw withstands the vibration, temperature extremes (-40°C to +85°C typical), and electrical transients common to 4WD engine bay mounting—superior to solenoid-based solutions prone to contact welding or voltage drop under sustained loads.
Baintech engineering and Australian design backed by 30+ years Bainbridge Technologies experience in 12V/24V power systems for harsh Australian touring conditions—designed specifically for corrugated tracks, bull dust, extreme heat, and extended remote operation where electrical reliability is critical to safe travel.
Technical Specs
- Part number: Not specified (Baintech Voltage Control Relay 12V/24V 100A)
- Manufacturer: Baintech (Bainbridge Technologies, Australia)
- Current rating: 100A continuous (automotive relay contact)
- Voltage compatibility: 12V DC and 24V DC (auto-sensing)
- Activation voltage: Preset threshold (typically 13.3V for 12V systems, 26.6V for 24V)
- Deactivation voltage: Below activation threshold or ignition-off signal
- Relay type: Voltage-controlled high-current automotive relay
- Contact configuration: Single-pole single-throw (SPST) normally-open
- Terminal connections: High-current studs or lugs (cable gauge not specified)
- Operating temperature: -40°C to +85°C (typical automotive relay specification)
- Protection: Automatic isolation prevents start battery drain from auxiliary loads
- Mounting: Compact relay for engine bay, battery compartment, or under-vehicle mounting
- Wiring: Positive connection to start battery, auxiliary battery, and alternator sensing (diagram not provided)
- Weight: Not specified (compact automotive relay typically under 0.5kg)
- Compliance: Australian designed for local touring conditions
- Applications: 4WD dual-battery, caravan auxiliary battery, motorhome house battery, marine auxiliary, commercial vehicle auxiliary power
Frequently Asked Questions
How does this differ from a basic solenoid isolator?
The Baintech relay uses voltage sensing to intelligently manage charging priority, ensuring the start battery reaches healthy charge before directing power to auxiliaries. Basic solenoids operate on ignition signal only, potentially charging auxiliary batteries while the start battery remains depleted—this relay prevents that failure mode.
Can I use this with lithium auxiliary batteries?
Yes, the voltage-sensing relay works with lithium (LiFePO4) auxiliary batteries. However, lithium batteries may require specific charging profiles from your DC-DC charger in parallel with this relay. The relay manages isolation, while a DC-DC charger should handle lithium-specific charging algorithms for optimal battery longevity.
Will this work with my alternator's smart charging system?
Modern smart alternators (Ford, Toyota, Mazda) with variable voltage output work with this relay, though performance may vary depending on alternator voltage profiles. For vehicles with smart alternators, consider adding a DC-DC charger in conjunction with this relay to ensure consistent auxiliary battery charging.
What size cable do I need for 100A installation?
For 100A continuous current over typical 4WD wiring runs (2-5m), use minimum 6mm² (10AWG) cable, though 10mm² (8AWG) is recommended for voltage drop minimization. Ensure all connections are crimped or soldered with heat-shrink covering—no twist-and-tape connections at 100A current levels.
Does this replace a DC-DC charger or battery management system?
No, this relay provides isolation and basic split charging but doesn't regulate charging voltage/current like a DC-DC charger. For optimal lithium battery charging, solar integration, or advanced battery management, this relay works alongside (not instead of) a DC-DC charger or battery management system.
Compatible With / Goes Well With
- Dual-battery 4WD systems (Toyota LandCruiser, Nissan Patrol, Ford Ranger, Isuzu D-MAX)
- Caravan and motorhome auxiliary battery banks (12V house systems)
- Marine auxiliary battery systems (boats with house battery separate from start)
- Commercial vehicle auxiliary power (trucks, buses, mobile workshops)
- AGM auxiliary batteries (deep-cycle for camping and touring applications)
- Lithium (LiFePO4) auxiliary batteries (with appropriate DC-DC charging)
- DC-DC battery chargers (Redarc, Projecta, CTEK) for advanced charging control
- Pure sine wave inverters (1000W-3000W) powered from auxiliary battery
- Portable fridge/freezers (Dometic, Engel, ARB) running from auxiliary power
- 12V camping electrical accessories (LED lighting, water pumps, USB chargers)
- Battery monitoring systems (Victron BMV, Redarc gauges) for state-of-charge tracking
- Solar panels and regulators (supplementary charging for auxiliary batteries)
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