Combine solar and alternator charging
A REDARC BCDC1240D accepts roof solar and vehicle power through one charger, feeding an AGM house battery and fridge.
Follow the circuit
01
Two inputs, one output
The BCDC prioritizes available solar, then supplements it from the vehicle. Its two inputs do not provide two independent 40 A outputs.
02
Keep solar unregulated
The yellow solar input uses the BCDC’s own regulator. Connect an unregulated panel, rather than the output of another solar controller.
03
Trace the common return
Vehicle, panel and house negatives meet at the common return. Crimp shows separate logical terminals for the charger’s shared black lead.
The source and this example
Rebuilt from REDARC’s BCDC Dual Input manual, figure 2.7.1.1: the lead-acid battery setup with solar and vehicle inputs.
A 100 W panel, 200 Ah AGM battery and fridge replace unspecified source equipment. Crimp adds a PV disconnect; control wires and vehicle chassis routing are explained separately.
- REDARC BCDC Dual Input manual ↗
Manufacturer manual linked from REDARC’s downloads page; sections 2.4–2.8 and figure 2.7.1.1.
- REDARC common-ground wiring diagrams ↗
Common negative and vehicle chassis grounding requirements.
Before you build
- Verify cold panel voltage stays within the charger limit.
- Set the trigger and charge-profile wires, and use the vehicle’s approved ground point.
- Check the specified 60 A MIDI fuse installation at both batteries.
This is a planning example. Cable sizing uses Crimp’s ABYC-based method; the drawing does not certify an installation.
Cable sizes and connections · 10 conductors
Lengths are one way. Sizes and currents come from the same Crimp model as the drawing. Each drop value covers one drawn conductor; the full circuit includes its supply and return. AWG values are approximate counterparts to the metric areas.
| Connection | Length | Wire | Design current | Fuse | Drop |
|---|---|---|---|---|---|
| C1 · Renogy 100W Mono + → Solar DP Isolator IN + | 2.5 m | 16 mm²AWG 6 | 5.4 A | — | 0.08% |
| C2 · Renogy 100W Mono − → Solar DP Isolator IN − | 2.5 m | 16 mm²AWG 6 | 5.4 A | — | 0.08% |
| C3 · Solar DP Isolator OUT + → Redarc BCDC1240D PV + | 50 cm | 16 mm²AWG 6 | 5.4 A | — | 0.02% |
| C4 · Solar DP Isolator OUT − → Redarc BCDC1240D PV − | 50 cm | 16 mm²AWG 6 | 5.4 A | — | 0.02% |
| C5 · Vehicle supply + → Redarc BCDC1240D ALT + | 2 m | 16 mm²AWG 6 | 44.4 A | 60 A | 0.81% |
| C6 · Vehicle supply − → Redarc BCDC1240D BATT − | 2 m | 16 mm²AWG 6 | 44.4 A | — | 0.81% |
| C7 · Redarc BCDC1240D BATT + → Renogy 200Ah AGM Deep Cycle + | 80 cm | 16 mm²AWG 6 | 40 A | 60 A | 0.29% |
| C8 · Redarc BCDC1240D BATT − → Renogy 200Ah AGM Deep Cycle − | 80 cm | 16 mm²AWG 6 | 40 A | — | 0.29% |
| C9 · Renogy 200Ah AGM Deep Cycle + → Fridge + | 2 m | 4 mm²AWG 11 | 5 A | 15 A | 0.36% |
| C10 · Renogy 200Ah AGM Deep Cycle − → Fridge − | 2 m | 4 mm²AWG 11 | 5 A | — | 0.36% |
A dash means no fuse is assigned to that conductor; upstream protection may apply. Recheck the exact device, holder and placement after edits.
Equipment · 6 components
- Renogy 100W Mono
18.6 V · 5.38 A rated / planning output · 100 W · 22.3 V STC Voc
100W compact rigid mono panel, legacy RNG-100D-SS version with Vmp 18.6V, Voc 22.3V and Isc 5.86A. 1076×509×35mm, 6.5kg, 14 AWG solar leads; 15A maximum series fuse. Check the label because later versions use different voltages.
- Solar DP Isolator
Double-pole isolator switch — breaks both the positive and negative solar legs simultaneously for safe panel disconnect.
- Vehicle supply
12 V · 80 Ah
Cranking battery for diesel/petrol engine.
- Redarc BCDC1240D
40 A rated / planning output
BCDC1240D: red vehicle input, yellow solar input, brown battery output, black common negative. Catalog PV− and BATT− represent that shared negative. Trigger/profile control wires are outside the power drawing.
- Renogy 200Ah AGM Deep Cycle
12 V · 200 Ah
Crimp-selected AGM battery, 60 A charge limit. The source's unspecified solar array and load are represented by a Renogy 100 W panel and fridge. All lengths are assumptions.
- Fridge
5 A load allowance
Built-in CRX50 compressor fridge with removable freezer compartment. Rated 5A at 12V or 2.6A at 24V; compressor duty varies with temperature and ventilation. Dometic specifies a 15A protected DC supply at 12V, or 7.5A at 24V, and an open rear ventilation path.
Crimp checks · 2 findings to review
These are the current engine findings for the saved example. They remain visible when you open it in Crimp.
- warning: Check fuse suitability: 200Ah AGM
- warning: Check fuse suitability: Vehicle supply
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Crimp for AI agents · public beta
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