Charger
REDARC BCDC1240D wiring diagram
Plan the starter-to-auxiliary-battery wiring for a REDARC BCDC1240D Classic40. See the battery fuses and common return, then adapt the example to your dual-battery setup.
- Rated output
- 40 A
- PV open-circuit limit
- 32 V
Wiring diagram
How the BCDC1240D 40A is wired.
Open this example in Crimp to use your own parts and cable lengths. Review the assumptions and installation notes as you adapt the circuit.
The starter uses the manual's 60 A battery fuses, a 16 mm² conductor choice above its minimum area, and a 1 m charger-to-auxiliary-battery run. These are pinned example choices; review them after edits. The engine's generic DC-DC input-current estimate does not model this charger's voltage conversion or solar sharing. Manufacturer installation manual
Edit this wiring exampleAuxiliary-battery sizing for this example
The editable example connects a vehicle battery to a 12 V auxiliary bank, with solar disconnected. These sizes describe the short charger-to-auxiliary-battery run; open the example to inspect both battery paths.
1 m one way
12 V system
- Wire
- 16 mm² · 6 AWG
- Example fuse
- 60 A
- Design current
- 40 A
- Voltage drop
- 0.7%
Sized against ABYC E-11. The design current is the unit's rated output. The length is one way; voltage drop includes an equal-length return.
Run-length and manufacturer assumptions
The editable example uses 3.048 m (10 ft) runs unless a shorter run is stated. Metric overviews round these to 3 m. Adapt the parts and lengths to your installation before choosing cable and protection.
The starter uses the manual's 60 A battery fuses, a 16 mm² conductor choice above its minimum area, and a 1 m charger-to-auxiliary-battery run. These are pinned example choices; review them after edits. The engine's generic DC-DC input-current estimate does not model this charger's voltage conversion or solar sharing. Manufacturer installation manual
Supporting parts
- 2 m total of 16 mm² (6 AWG) marine cable
- Terminations for 16 mm² cable, matched to the equipment's screw terminals, leads or studs
- 60 A fuse and holder on the positive run
- Heat-shrink, strain relief and terminal boots sized to the cable
Check stud sizes, fuse type, run length and how warm the space gets against the gear you actually have before you order.
Installation notes
Before you install.
Open a question for model-specific guidance and sources.
Verified against the manufacturer's documentation (rev. INST173-3 EN), checked 2026-09-11. Manufacturer documentation →
Which REDARC BCDC1240 is covered here?
This is the BCDC1240D, BCDC Classic40, a 40 A charger for a 12 V auxiliary battery. The D suffix matters. REDARC's model specification identifies separate vehicle and MPPT solar inputs, and 60 A protection on both battery paths. The vehicle can be 12 V or 24 V; the output is for a 12 V battery. Classic, Core and Alpha are separate product families.
How does the vehicle-to-auxiliary-battery path connect?
For a 4WD dual battery setup, the starter battery supplies the red vehicle-positive lead through a battery-end fuse. The brown output lead charges auxiliary positive through its own battery-end fuse. The black lead is common ground. The starter models this vehicle path with a 12 V AGM source and 200 Ah auxiliary bank; solar is left disconnected.
All negative connections must share an electrical ground. On vehicles with starter-battery current sensing, the required return may be a designated chassis point rather than the battery-negative post. Use REDARC's common-ground diagrams and the vehicle's instructions. Crimp's logical negative connections are not a physical harness pinout.
What fuse and cable size does the BCDC1240D need?
The Classic manual, pages 6 and 14–16, specifies 60 A input and output fuses, recommends MIDI protection and requires at least 13.56 mm² conductor area for 1–5 m. The example selects 16 mm² and pins the manufacturer's fuse rating.
The auxiliary-battery run is 1 m (about 3.3 ft), following the short-output-run guidance. The vehicle feed is 3.048 m (10 ft). Each includes an equal-length return for the example calculation. The reference panel describes the output circuit; input current is a generic engine estimate, not a voltage-conversion or solar-sharing simulation. Replace placeholder batteries and review pinned hardware after changing the layout.
What about solar and a smart alternator?
Yellow accepts unregulated solar; select the blue trigger and orange battery-profile connections from the manual. These control wires and optional solar are outside the starter. A removable canopy or caravan also needs a common return across its connector; use the separate manufacturer diagram for that layout.
Use the lithium conversion guide to plan battery changes and the fuse checker for fault-current and exact-part checks. The ABYC-based methodology does not establish AS/NZS installation compliance.
See the BCDC1240D dual-battery system example for the vehicle source, auxiliary bank, distribution and protected loads together, including unresolved protection checks.
- Use the wire size calculator to compare ampacity and voltage drop for your one-way run and installation conditions. Fuse selection remains separate.
- Check DC-DC charger size and vehicle headroom using actual input voltage, efficiency and battery/BMS limits before setting charging current.
Fit check
Connect it to the rest of your system.
Describe your setup to draft a system with BCDC1240D connected. Review the selected parts and cable lengths, then edit the diagram in Crimp.
The model only picks parts and draws the connections. Every wire size and fuse rating still comes from Crimp's own sizing, never from the model.
Enable JavaScript to describe your system.
Technical reference
Specifications and terminal map.
Check the model, ratings and connection points against your own unit before choosing installation hardware.
Catalog specification
Dual-input 40A DC-DC charger with MPPT solar input. Vehicle input accepts 9–32V so it runs under 12V or 24V alternators; Redarc specifies a 60A input fuse.
- Rated output
- 40 A
- Planning charge current
- 40 A
- PV open-circuit limit
- 32 V
Terminal map
These are logical circuit connections. ALT + maps to the red vehicle lead, PV + to yellow, and BATT + to brown. PV − and BATT − represent the shared black ground connection, not separate physical negative leads. The listed currents are catalog planning limits, not manufacturer wire ratings. Trigger and profile wires are described in the installation notes.
ALT +
positive · input
PV +
positive · input
PV −
negative · input
BATT +
positive · output
BATT −
negative · output
Sources and sizing method
Equipment specifications. Model details, ratings and terminal roles come from the catalog. Check your unit’s label and current manufacturer documentation for its exact revision.
Example sizing. Sized against ABYC E-11. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. Results use the example current and run length shown above. Set your actual equipment, lengths and installation conditions in Crimp before choosing hardware.
Read how the sizing worksNext step
Plan your installation with BCDC1240D 40A.
Open this example as a new project, or add this component to your existing diagram. Use your equipment and cable lengths to review the sizing.
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