BMS12075
Redarc Manager Alpha75 wiring diagram
BMS12075 combines 75 A charging for a 12 V service battery from vehicle DC, solar, and AC. Solar array cold-weather Voc must stay below 48 V. Supplied battery monitoring and source-current setup are part of the installation.
- Rated power
- 1,200 W
- Rated output
- 75 A
- PV open-circuit limit
- 48 V
Wiring diagram
How the Alpha75 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.
Cable sizing for this example
Use the diagram as a starting point for your installation. Replace the example equipment and cable lengths with your own, and check the connections against your exact model's instructions.
3 m one way
12 V system
- Wire
- 25 mm² · 4 AWG
- Example fuse
- 100 A
- Design current
- 75 A
- Voltage drop
- 2.7%
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.
Supporting parts
- 6.1 m total of 25 mm² (4 AWG) marine cable
- Terminations for 25 mm² cable, matched to the equipment's screw terminals, leads or studs
- 100 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. INST333-7), checked 2026-10-01. Manufacturer documentation →
Which Manager Alpha is this?
BMS12075 combines AC, vehicle, and solar charging for a 12 V auxiliary bank, with 75 A total output. This is the Manager Alpha, not a BCDC Alpha charger. The manual covers regional AC leads and specifies 95–264 VAC, 45–65 Hz input; use the genuine lead for the region and an earthed outlet. The 75 A rating is shared across sources, not additive.
How do the connections map?
The physical power studs are START, SOLAR, AUXILIARY, and GROUND. Crimp's ALT + represents START and must connect to the start battery, not directly to an alternator output. PV + maps to SOLAR and BATT + to AUXILIARY. Negative symbols represent the common-ground arrangement; the manufacturer system diagram includes a separate battery monitor that must be the only connection to auxiliary battery negative. Loads and charging returns connect on its system side.
The drawing omits R-Bus, its terminator, the ignition signal, battery sense, and the complete monitor wiring. AC L/N/earth describe the mains interface, not permission to replace the supplied cable with exposed wiring.
What protection is specified?
For the full 75–82 A design-current row, page 12 specifies 100 A auxiliary-battery and 125 A starter-battery MIDI/MEGA fuses. Install each battery fuse within 150 mm cable length of its positive terminal. Auxiliary and main ground cables must be no longer than 2 m.
The cable table has separate insulation, engine-bay, and lug-adapter footnotes; do not take its smallest cross-section without those conditions. Set the DC current limit and maximum charge current no higher than the installed cable/fuse design, and consider locking the settings against accidental increases.
What are the input and battery limits?
The BMS12075 column specifies 9–32 V vehicle input, 9–48 V solar input, 82 A maximum input current, and 1500 W maximum solar array. Cold-weather array Voc must stay below 48 V. Connect unregulated panels; an additional panel regulator is not part of this input design.
Select the correct battery type and capacity. Use the heated-lithium profile only with a functioning battery heater; otherwise select standard lithium. Set ignition/D+ and DC trigger behavior for the actual alternator. Serial numbers starting 2606 or later add the documented 24 V starter recovery/back-charge capability.
Where can it be installed?
Install the main unit, monitor, and display in a dry indoor vehicle living area, not the engine bay. Keep swarf barriers fitted during installation, then remove them before operation. Retain ventilation and access to the terminals and monitor.
Fit check
Connect it to the rest of your system.
Describe your setup to draft a system with BMS12075 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.
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Technical reference
Specifications and terminal map.
Check the model, ratings and connection points against your own unit before choosing installation hardware.
Catalog specification
BMS12075 combines 75 A charging for a 12 V service battery from vehicle DC, solar, and AC. Solar array cold-weather Voc must stay below 48 V. Supplied battery monitoring and source-current setup are part of the installation.
- Rated power
- 1,200 W
- Rated output
- 75 A
- Planning charge current
- 70 A
- PV open-circuit limit
- 48 V
Terminal map
Catalog connection points, current direction and planning limits. Check the manufacturer's pinout and connector ratings before installation.
START +
positive · input
PV +
positive · input
GROUND (common)
negative · input
AC L
neutral · input
AC N
neutral · input
AC ⏚
ground · bidi
BATT +
positive · output
GROUND (common)
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 Alpha75.
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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