Charger
Plan the starter-to-auxiliary-battery wiring for a REDARC BCDC1250D Classic50. 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.
1 m 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 →
The BCDC1250D is the BCDC Classic50, with a 50 A rated output to a 12 V auxiliary battery. REDARC's 1250D specification confirms 12 V or 24 V vehicle input, solar priority and an additional SoftStart charging stage. Its output differs from the 40 A BCDC1240D, although both specify 60 A battery fuses. This page does not cover Alpha50 or Core models.
Starter-bank positive feeds red through its fuse; brown connects through a second fuse to auxiliary positive. Black is common ground. Yellow is optional unregulated solar input. Check the battery's permitted charge current before choosing this larger charger.
The editable example uses a 12 V AGM starter bank and a 200 Ah auxiliary bank, with solar disconnected. Its output circuit is sized at this model's own 50 A rating. Battery capacity is a placeholder, not proof of charging-current acceptance. The engine does not simulate SoftStart, alternator headroom at idle or the charger's combined-input control.
The Classic manual lists 60 A vehicle-input and output fuses for the 1250D. Its cable row requires at least 13.56 mm² for 1–5 m, increasing for longer routes. The starter pins 16 mm² and 60 A battery fuses, with a 1 m output run and 3.048 m (10 ft) vehicle feed. Calculations include equal-length returns.
Mount near the auxiliary battery with airflow and away from concentrated engine-bay heat. A suitable charger location does not establish that your lithium battery belongs there. Review both manufacturers' requirements.
Use a common negative for the charger, batteries and any solar source. REDARC's grounding guidance explains why some smart-alternator vehicles require a chassis connection that preserves starter-battery current sensing. A detachable auxiliary bank needs that return carried through its connector too.
Select blue trigger and orange battery-profile wiring using the manual's vehicle and battery instructions. The starter only draws heavy power paths; its logical negative terminals and omitted control wires are not a physical harness pinout.
Review the conversion guide for the surrounding system and the fuse checker for exact fuse/holder and fault-current evidence. Crimp's methodology explains its ABYC-based calculations; Australian dual-battery terminology does not imply AS/NZS coverage.
Build it out
Add BCDC1250D 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. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. 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.