REDARC BCDC® Core Dual Input Multi-Stage In-Cabin Battery Charger

Product Overview

The BCDC Core 25 and BCDC Core 40 are three-stage, DC-DC 12V auxiliary battery chargers that source power from both the vehicle's alternator and solar panel input. The BCDC Core's vehicle input is suitable for 12V or 24V start battery and alternator systems, while the solar input is designed for connection to unregulated 12V nominal solar panels. As a true dual input charger with an in-built MPPT regulator, the unit charges simultaneously from solar and alternator with Green Power Priority to minimise load on the vehicle alternator.

The BCDC Core compensates for the input voltage of either power source, always outputting the ideal voltage to charge the selected battery type. This capability makes it ideal for charging a wide variety of auxiliary 12V batteries, including Lithium batteries, and overcomes voltage drop over long cable runs.

In addition, BCDC Core features an internal battery isolator that disconnects the auxiliary battery system from the start battery based on voltage. This allows the charger to safely charge the auxiliary battery from the vehicle and prevents the start battery from being excessively discharged.

All these features are combined in a compact, lightweight housing to suit mounting within vehicle cabins and battery boxes.

BCDC Core Unit Components:

• 1. BCDC Core Unit
• 2. Wires (See Section 1.1 for wiring information)
• 3. Profile LEDs: Displays the charge profile of the BCDC.
• 4. Status LEDs: Displays the charge status of the BCDC.

Cables and Wires

The BCDC Core Battery Chargers are equipped with a fly lead wiring harness that must be correctly connected to ensure effective charging of the auxiliary battery. Refer to Section 3.2.1 and Section 3.7 for typical BCDC Core Battery Charger setups and wire installation details.

Charge Profile LEDs

The BCDC Core features four different charging profiles designed to suit your battery's charging requirements: AGM/Gel (A), Standard Lead Acid (B), Calcium (C), and Lithium (Li). Refer to the charging specifications stated by the battery manufacturer and the installation temperature chart before selecting the profile.

Profile LEDs:

• A: AGM/Gel
• B: Lead Acid
• C: Calcium
• Li: Lithium

A solid Profile LED indicates the unit is ON and charging. A flashing profile LED indicates the unit is in standby mode and ready to charge when the vehicle is turned on.

Charge Status LEDs

The Charge Status LEDs indicate which inputs are available and the stage of the charge process.

Solar & Vehicle LEDs

The Solar and Vehicle LEDs are ON when the input is available and in use, and OFF when the input is not available or not in use. If the LEDs are flashing, refer to Section 4.1.

Stage LED

The Stage LED indicates the Charge Profile Stage. The charger outputs a 3-Stage charging profile: Boost, Absorption, and Float Stages.

Product Function

Charging Stages

Boost: The charger maintains a constant current until the battery voltage reaches its Absorption Voltage. Current may vary to maintain safe operating temperature or limit voltage differences.

Absorption: The charger maintains a constant voltage for a preset period or until the current drawn by the battery drops to a predetermined level for 30 seconds, after which it enters the Float stage.

Float: Maintains 13.3V (13.6V for LiFePO4) on the output battery, keeping it topped up. This counteracts self-discharge or loads. When the battery loses charge, the charger moves back to the Boost stage.

Diagram: Charging Stages (Voltage and Current over time, showing Boost, Absorption, Float)

The BCDC has automatic timeouts to prevent overcharging. If a timeout occurs before the battery is fully charged, the process restarts from the Boost stage after a brief rest period. Li profile timeouts are designed for optimal charging of large lithium battery banks.

CAUTION: When charging Lithium Iron Phosphate batteries, ensure they have an inbuilt battery management system with under/over voltage protection and cell balancing.

Battery Test Mode

The charger enters a battery test mode every 100 seconds to verify input validity and auxiliary battery connection. This protects the vehicle start battery from over-discharge and the vehicle/wiring from damage.

Green Power Priority

This automatic function prioritises input sources, ensuring maximum power from solar panels before supplementing from other sources. This reduces load on the vehicle alternator and maximises solar energy collection.

Charging Source Priority:

1. Solar (unregulated, 12V solar panel)
2. Alternator (via the Start Battery while the vehicle is running)

Diagram: Green Power Priority showing Solar panel connected to BCDC Core, which is connected to Auxiliary Battery, with Alternator/Start Battery also connected to BCDC Core.

Installation

Planning Installation

CAUTION: The heatsink can reach up to 60°C/140°F. Install the unit where it won't contact users or highly flammable material.

Mounting Location

The BCDC Core is designed for installation within the vehicle cabin, ute canopy, caravan, or battery box. It operates optimally below 55°C/130°F with good airflow. At higher temperatures, output current derates, and the unit turns OFF at 80°C/175°F.

IMPORTANT: Do not mount the BCDC Core in the engine bay due to moisture and heat damage risks.

Mount the charger as close as possible to the auxiliary battery, with no more than 1m of cable length. Ensure LED indicators are accessible for troubleshooting.

Diagram: Vehicle interior mounting (✅) vs. Engine bay mounting (❌).

Installation Overview

Refer to the diagrams for planning required cabling, fusing, and connections. REDARC recommends installation by a suitably qualified person.

Typical Battery Setup Diagram

Diagram: Shows a 12V Solar Panel Array connected via a fuse to the BCDC Core. The BCDC Core is connected via a fuse to the Auxiliary Battery. The Vehicle's 12V or 24V Start Battery is connected via a fuse to the BCDC Core. Includes connections for ignition, ground, and optional LED.

Considerations Prior to Installation

1. Auxiliary Battery Profile Selection: Determine battery chemistry to correctly connect the ORANGE wire for charge profile setting.
2. Fixed or Removable: Choose connectors (soldered splices for fixed, Anderson plugs for removable) based on installation needs.
3. Solar Panel Selection: Ensure panels are 12V nominal and do not have a built-in regulator.
4. Vehicle Alternator Type: For variable-voltage or idle-stop (smart) alternators, the BLUE wire connection is required. Check for a battery sensor on the start battery to identify smart alternators. Older vehicles or those with fixed voltage alternators do not require the BLUE wire.
5. Cable Length and Gauge: Determine cable requirements based on length and current. AWG, B&S, and GA are interchangeable terms for wire diameter.
6. Common Ground: Ensure the BCDC Core, auxiliary battery, start battery, and solar panels share a common electrical ground, typically connected to the vehicle body.
7. Auxiliary Battery Load Current: Determine loads and total current to size load cables and fuses correctly.

What You Will Need

Tools:

• Screwdriver set
• Spanner set
• Socket set
• Pliers
• Side cutters
• Cable cutters
• Ratcheting or Hydraulic crimping tool
• Soldering Iron

Consumables:

• Cabling
• Cable connectors, lugs and terminals
• Fuses
• Electrical tape
• Heat Shrink
• Cable ties
• Conduit/Split tubing
• Wires
• Fasteners

Additional fixings (nuts, bolts, self-tapping screws) and battery post clamps may be required.

Cable Sizing

The BCDC Core 25 and 40 handle peak currents up to 35/55A. Wire gauge depends on cable run length. Refer to Table 3 for cable thickness requirements.

NOTE: The Brown Output cable should be at maximum 1m (3.9') in length.

Cable Connections

Ensure good, low resistance electrical connections that will not degrade over time.

CAUTION: Poor connections can lead to wire insulation breakdown, short circuits, or fire. REDARC recommends this activity be undertaken by an appropriately trained person.

For extending cables, REDARC recommends soldered butt-splice crimp connections covered with heat shrink.

Diagram: Steps for Crimping using Butt-Splices (Slide heatshrink, insert wires, crimp, solder, cool, apply heatshrink).

Lug Connections

Cable lugs are commonly used. Strip approximately 12-14mm of insulation, insert wires into the lug, and crimp correctly. Do not use standard pre-insulated connectors for 8 B&S cables as they are not rated for the current. REDARC fuse kits include 4x10mm² (8 B&S) crimp lugs. Anderson™ SB50 connectors are suitable for cables requiring disconnection (e.g., portable battery boxes).

Diagram: Typical Cable Connectors - Portable Auxiliary Battery System (showing connections from Vehicle Battery, BCDC Core, and Auxiliary Battery using various connectors like Anderson SB50).

Diagram: Typical Cable Connectors - Fixed Auxiliary Battery System (showing similar connections but with soldered butt splice).

Fusing

Fuses are required to protect the RED Vehicle Input cable and the BROWN Output cable. Mount the RED cable fuse within 100mm (3.9") of the start battery positive terminal, and the BROWN Output cable fuse within 100mm (3.9") of the auxiliary battery positive terminal. Refer to Table 4 for fuse sizing.

REDARC recommends MIDI style bolt-down fuses for low resistance connections. Blade type fuses are not recommended due to high resistance and heat generation. Self-resetting circuit breakers are also not recommended as they may trip prematurely.

Diagram: MIDI Style Bolt-Down Fuse and MIDI Fuse Assembly.

Mounting

WARNING: Use suitable Personal Protective Equipment when operating power tools.

Ensure the mounting location is structurally sound. Use 4 x M6 or similar fasteners to secure the BCDC Core. Ensure LED indicators are accessible for troubleshooting.

Diagram: Mounting the Charger showing screw points.

Cable and Wire Installations

NOTE: Ensure cabling is clear of sharp edges or moving parts and has enough slack for flexing to prevent damage.

REDARC recommends using cable ties and conduit or split tubing to manage cabling.

Output Auxiliary Battery — BROWN Cable

Connect the BROWN cable to the MIDI fuse, then to the auxiliary battery's positive terminal. Ensure the cable length from the charger and fuse to the battery is within 1m (3.9').

Diagram: Connecting the BROWN Cable to the Auxiliary Battery Input.

Common Ground – BLACK Cable

Connect the BLACK wire to a ground point common to both the start and auxiliary batteries, typically the vehicle bodywork.

Diagram: Connecting the BLACK cable to a common ground point.

Profile Selection – ORANGE Wire

Connect the ORANGE wire to set the maximum output voltage according to the selected Charge Profile. If not used, tape over the end of the wire.

CAUTION: Ensure the selected Maximum voltage does not exceed the battery manufacturer's recommendation.

Diagram: Setting the Maximum Voltage (ORANGE wire) showing four profiles: PROFILE A (ORANGE disconnected), PROFILE B (ORANGE to Common Ground), PROFILE C (ORANGE to RED Cable), PROFILE Li (ORANGE to GREEN wire).

Vehicle Input – RED Cable

Connect the RED cable to the MIDI fuse, then to the start battery's positive terminal. Ensure the MIDI fuse is within 100mm (3.9") of the start battery.

Diagram: Connecting the RED cable to the Start Battery Input.

Vehicle Ignition Input – BLUE Wire

The BLUE wire is required for Low Voltage mode with variable-voltage alternators. If not used, tape over the end.

LOW VOLTAGE MODE: Connect BLUE wire to IGN for continuous idle vehicles, or to D+ for idle-stop vehicles. This mode improves auxiliary battery charging by widening the voltage range. For most vehicles, the 'Ignition ON' signal is sufficient.

STANDARD VOLTAGE MODE: Leave BLUE wire disconnected or connect to Ground. Used for vehicles with fixed voltage alternators. The BCDC measures start battery voltage via the RED wire and charges within standard thresholds.

Diagram: Connecting the BLUE wire showing LOW VOLTAGE MODE (to IGN or D+) and STANDARD VOLTAGE MODE (disconnected or to Ground).

Input Mode Charging Thresholds Table: Details ON/OFF voltage thresholds for 12V and 24V inputs in Standard and Low Voltage modes.

BLUE WIRE INSTALLATION USING A RELAY: An ignition-switched relay can be used if running the ignition signal (BLUE wire) to the BCDC is difficult. A relay can be added to the Vehicle Input (RED cable) controlled by a vehicle ignition signal. Connecting the BLUE wire to the BCDC Core's RED wire enables Low Voltage Mode.

Diagram: Installation Using a Relay showing a RK1260 relay connected between the vehicle ignition and the BCDC Core's RED and BLUE wires.

Solar Panel(s) – YELLOW Cable

The YELLOW wire connects solar input. If solar is not installed, tape over the end. IMPORTANT: Do not connect solar panels with inbuilt regulators. Most residential panels exceed the BCDC's 32V input limit.

Connecting Multiple Solar Panels

Connect multiple 12V solar panels in parallel to maintain output voltage while increasing power. Size cables correctly.

Diagram: Connecting solar panels in parallel.

The BCDC Core can handle solar arrays with higher wattage than its maximum output rating; it will automatically limit power.

Optional LED – GREEN Wire

The GREEN wire connects to an external LED (optional) for A, B, C profiles, or to the ORANGE wire for Lithium profile selection. If connected to an LED, it indicates charging status (OFF when not charging, ON when charging). If the LED flashes, refer to Section 4.1.

NOTE: Use a standard 12V LED with an integrated resistor (1kΩ for 12V, 2.2kΩ for 24V).

Diagram: Connecting the GREEN wire showing connections for PROFILE A, B, C (to optional LED) and Li PROFILE (to ORANGE wire).

Maintenance

Regularly check wiring and cable connections to ensure they are secure and to prevent damage to the BCDC Core, auxiliary battery, and start battery.

Troubleshooting

No LEDs ON

Indicates no output battery connection (BROWN wire) AND no input connection (YELLOW/RED wire).

1. Check all wiring to the charger and battery, especially the Ground (BLACK wire).
2. Check fuses are intact and properly connected.

If problems persist, contact your local Auto-Electrician.

Charge Profile LED Flashing

Indicates standby mode due to no valid charging source (input below turn-on threshold) or no connection to the auxiliary battery.

1. Check Vehicle (RED) and/or Solar (YELLOW) wire connections.
2. Check Ground (BLACK) wire connection to auxiliary battery and chassis earth.
3. Check all wiring to the auxiliary battery, especially the Ground.
4. Check fuses are intact and properly connected.

Solar Connected, Solar LED OFF

Indicates required turn-on conditions are not met: Open Circuit Voltage at YELLOW wire is below 9V, or insufficient solar power.

1. Check sunlight levels.
2. Ensure solar panel is not shaded.
3. Verify voltage at YELLOW wire is above 9V.
4. Check all wiring to the Solar Panel, especially the Ground.
5. Ensure an unregulated solar panel is used.

Allow up to 2 minutes for the unit to recognise input changes.

Vehicle Connected, Vehicle LED OFF

Indicates required turn-on conditions are not met, or the Solar input is supplying full power.

• With BLUE wire unconnected: RED wire voltage must be > 12.9V (12V) or > 25.8V (24V).
• With BLUE wire connected to Ignition: Ignition must be ON, and RED wire voltage must be > 12.0V (12V) or > 24.0V (24V).

1. Check that the vehicle is running.
2. Verify voltage on the RED wire meets the required threshold.
3. Check all wiring to the Vehicle battery, especially the Ground wire (BLACK).
4. Check auxiliary battery and ground connection.

If problems persist, contact your local Auto-Electrician.

Error Codes

If a fault occurs, ALL LEDs will flash to indicate the fault type.

Turn On/Off Thresholds

Table 10 provides detailed voltage thresholds for input trigger settings, open circuit low voltage conditions, loaded low voltage conditions, input overvoltage shutdown, and output undervoltage shutdown for 12V and 24V vehicle inputs and solar inputs.

Frequently Asked Questions

Q: The BCDC Core turns ON at 12.9V (12V) and OFF at 12.7V (11.9V), but it operates down to 9V, explain?

A: The BCDC Core briefly turns OFF every 100 seconds to measure the unloaded battery voltage. This allows it to accurately detect if the actual battery voltage has dropped below 12.7V (11.9V). At any other time, if the voltage drops below 9V, the unit will turn OFF.

Q: How does the BCDC Core charge an Auxiliary battery at 14V when it only gets 9V in?

A: The BCDC Core can act as both a reducer and a booster, operating from voltages above, equal to, or below the desired output. Its microprocessor control allows it to output a REDARC proprietary charging algorithm, enabling it to charge specific battery types even with low input voltage due to voltage drop.

Q: Where should I mount the BCDC Core Unit?

A: Mount as close as possible to the auxiliary battery. For caravans or campers, the battery compartment is ideal. Mounting to a metal surface can aid heat dissipation but is not crucial.

Q: What does the charger do if the temperature rises above its operating temperature?

A: The charger gradually decreases its output current capacity to protect both the battery and the unit.

Q: If I use the BCDC Core to charge my auxiliary battery, do I still need to install a battery isolator?

A: No, the BCDC Core incorporates the functionality of a battery isolator. It turns ON when it senses the vehicle has started and OFF when the vehicle is turned OFF.

Q: I've heard you shouldn't charge two batteries of different chemistries from the same source. Will I have problems charging my AGM or Gel auxiliary battery from my Lead Acid start battery?

A: The BCDC Core is a DC-DC Battery Charger, not a simple battery isolator. Its output is tailored to the selected auxiliary battery type, allowing optimal charging regardless of the start battery's chemistry.

Q: My BCDC Core is set up for 12V Alternator input but will not start when the vehicle is turned On. What's the problem?

A: The most likely cause is the BCDC Core being stuck in 24V mode. Try disconnecting the Vehicle (RED) and Output (BROWN) wires and reconnecting them. If the problem persists, contact REDARC.

Q: Can the BCDC Core charge from Solar and Vehicle power at the same time?

A: Yes. It prioritises the Solar source and supplements with Vehicle source power when available.

Q: Can the BCDC Core operate with only a single power source input?

A: Yes. It functions as a stand-alone solar regulator when only the Solar (YELLOW wire) is connected, or as a DC charger when only the Vehicle (RED wire) is connected.

Specifications

*¹ Voltages Specified are ± 100 mV.

Warranty

Limited Warranty

For full warranty terms and conditions, visit the REDARC website: www.redarcelectronics.com/warranty

Australia, New Zealand & Europe

REDARC Electronics Pty Ltd
23 Brodie Road (North),
Lonsdale SA 5160
Australia

• Australia: +61 8 8322 4848
• New Zealand: +64-9-222-1024
• UK & Europe: +44 (0)20 3930 8109

North America

REDARC Corporation
c/o Shallco, Inc.
308 Component Dr.
Smithfield, NC 27577
USA

• USA: +1 (704) 247-5150
• Canada: +1 (604) 260-5512
• Mexico: +52 (558) 526-2898

Checking the Product Serial Number

The Product Serial Number is located on the Main Unit and on the product packaging.

© REDARC Electronics Pty Ltd. All rights reserved. REDARC®, THE POWER OF REDARC®, and BCDC® are trademarks of REDARC Electronics Pty Ltd.