REDARC BCDCN1240 In-Cabin DC-DC Charger

Product Overview

The REDARC BCDCN1240 Core is a 40A in-cabin DC-DC charger designed to keep your auxiliary battery fully charged from both alternator and solar. It combines a DC-DC charger, MPPT solar regulator, and battery isolator into one compact, lightweight unit. Designed for modern vehicles with smart alternators, it ensures a consistent charge even when alternator output voltage fluctuates.

Capable of working with 12V or 24V vehicle systems and unregulated 12V solar panels, the BCDCN1240 automatically prioritises solar input to reduce strain on your alternator and maximise renewable energy capture. Its three-stage charging algorithm (Boost, Absorption, Float) ensures auxiliary batteries are charged to 100% for maximum lifespan and performance. Supported chemistries include AGM, Gel, standard lead acid, calcium, and LiFePO₄ lithium with built-in BMS protection.

For installers, the BCDCN1240 has clearly labelled heavy-duty fly leads and is designed for mounting inside cabins, canopies, caravans, or battery boxes. It should not be installed in engine bays. Cable sizing is crucial: for runs up to 5 m, 6 B&S (13.6 mm²) cable is recommended, while longer runs up to 9 m should use 4 B&S (25 mm²) to handle the charger’s 55 A maximum current. Both the input (vehicle battery) and output (auxiliary battery) connections require MIDI fuses rated at 60 A, mounted within 100 mm of each battery’s positive terminal. REDARC FK60 fuse kits are recommended to ensure low resistance and reliable connections.

To optimise performance with smart alternators, the ignition (blue) wire should be connected to an ignition or D+ source. Without this connection, charging may be inconsistent on Euro 6 and later vehicles. The charger overcomes voltage drop on long cable runs, making it particularly suitable for dual battery setups where the auxiliary battery is mounted in a trailer or canopy several metres from the start battery. Only unregulated 12V solar panels should be connected to the solar input — using regulated panels can cause inefficient charging as they interfere with the in-built MPPT regulator. Proper grounding of all components (vehicle start battery, auxiliary battery, charger, and solar) to a common earth is required for stable operation.

Key Features

• 40A dual input DC-DC charger with integrated MPPT solar regulator
• Charges from alternator and solar simultaneously with Green Power Priority
• Supports AGM, Gel, Standard Lead Acid, Calcium, and LiFePO₄ batteries
• Three-stage charging: Boost, Absorption, Float
• Automatic battery isolator prevents start battery discharge
• Overcomes voltage drop for remote auxiliary batteries (trailers, canopies)
• Thermal management with output de-rate above 55°C and shutoff at 80°C
• Comprehensive protection: reverse polarity, over-voltage, under-voltage, overheating

Technical Specifications

Electrical Ratings

Note: Cable size must be selected based on the total run length from start battery to charger and charger to auxiliary battery. Fuses should be mounted within 100 mm of both the start battery positive terminal and the auxiliary battery positive terminal. Only unregulated 12V solar panels should be connected to the solar input — using regulated panels can cause inefficient charging. Ensure all components (start battery, auxiliary battery, charger, and solar panels) share a common ground to vehicle chassis.

Why Choose the BCDCN1240?

The REDARC BCDCN1240 provides reliable, efficient charging for off-grid power systems. Its robust design incorporates DC-DC charging, MPPT solar regulation, and battery isolation in one unit, simplifying installation and ensuring safe, effective power delivery.

By including correct fuse protection and appropriately sized cabling, the BCDCN1240 is capable of delivering its full 40A output over long distances without voltage loss. It is a trusted choice for serious touring setups where battery reliability directly supports travel comfort and safety.