Charger
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.
Open this example as a new project. Use your own parts and cable lengths to make the plan yours.
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.
3.3 ft one way
12 V system
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.
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
Wiring diagram
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 exampleInstallation notes
Guidance for this model, with sources linked beside the relevant advice.
Verified against the manufacturer's documentation (rev. INST173-3 EN), checked 2026-09-11. Manufacturer documentation →
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.
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.
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.
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.
Build it out
Add BCDC1240D to your diagram, then connect your batteries, chargers and loads. Crimp calculates cable sizes and checks the connections as you draw.
Every cable you draw there is sized against ABYC E-11, from the same tables as the reference on this page.
Technical reference
Check the model, ratings and connection points against your own unit before choosing installation hardware.
Check stud sizes, fuse type, run length and how warm the space gets against the gear you actually have before you order.
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 +
alt-pos
positive · input
PV +
pv-pos
positive · input
PV −
pv-neg
negative · input
BATT +
out-pos
positive · output
BATT −
out-neg
negative · output
Method & provenance
Manufacturer specifications describe the equipment. Crimp calculates cable results from the circuit and assumptions you enter.
From the maker
Manufacturer, model, ratings and which terminal does what come from the catalog. A newer revision, or the nameplate on the unit in your hand, can say something different — when it does, the nameplate wins.
ABYC E-11
Sized against ABYC E-11 — the US reference, and what Transport Canada accepts as an alternative to TP 1332 for pleasure craft under 24 m. The run length and the current above are what drive the result. Crimp doesn't know how warm your space gets; draw the cable inside an engine-bay zone on the canvas and it sizes for the heat.
Next step
Open this example as a new project. Add your equipment and cable lengths, then review the sizing and checks for your setup.