Charger
Dual-input 50A DC-DC charger with MPPT solar input. Vehicle input accepts 9–32V for 12V or 24V alternators, fused at 60A per Redarc; solar takes panels up to 32V open-circuit.
The reference run on this page is 1 m one way, sized against ABYC E-11. Your own run will differ, and the canvas sizes that one.
Wiring diagram
The drawing shows where the feed, the return and the fuse land on this part. The starter uses the same reference circuit and sizing assumptions. Read the installation notes for manufacturer requirements before adapting the runs.
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
Open starter in CrimpBuild it out
Open the canvas with BCDC1250D already placed, then add your batteries, charging, distribution and loads around it.
Every cable you draw there is sized against ABYC E-11, from the same tables as the reference on this page.
Technical reference
The catalog facts for this part, which terminal takes what, and the hardware you'll want around it. Check the nameplate on your own unit before you order.
1 m reference run
12 V system
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 design current is the unit's rated output. The length is one way; voltage drop includes an equal-length return. The shared starter uses 3.048 m (10 ft) runs unless a shorter run is stated. These are example assumptions for you to adapt to your own installation.
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
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
Field notes
What we've read and heard about installing this exact part. These are notes, kept apart from the numbers Crimp works out.
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.
Verified against the manufacturer's documentation (rev. INST173-3 EN), checked 2026-09-11. Manufacturer documentation →
Method & provenance
The manufacturer publishes some of these numbers and Crimp works out the rest. It's worth knowing which is which.
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
It lands on the canvas already placed. Add what it connects to, and every run gets its wire and fuse as you draw.