Charger
Magnum Energy MSH3012RV Inverter/Charger wiring diagram
12 V pure sine inverter/charger with 3000 VA / 25 A total inverter output at 120 V, 60 Hz and 125 A battery charging. Two 50 A AC inputs share a neutral; only HOT 1 supplies the charger. Split-phase pass-through and hybrid load support need separate AC design. The 400 A DC draw is the manufacturer's maximum continuous input, not typical consumption; DC surge is unspecified. Follow the manual's 400 A time-delay battery protection and cable-length limits. AC grounding and neutral switching are not modeled.
- Nominal voltage
- 12 V
- Compatible systems
- 12 V
- Rated power
- 3,000 W
Wiring diagram
How the MSH3012RV 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.
12 V battery example for the original MSH3012RV. The manual specifies 400 A time-delay protection and at least 4/0 AWG (107.2 mm²) per polarity up to 5 ft / 1.524 m one way. The 1 m main conductors and 0.3 m disconnect link stay within that limit; the planner can choose larger wire for its conservative current/headroom assumptions. The 400 A DC value is maximum continuous input at low battery voltage, not typical draw at 12 V. Use the manual's 400 A fuse even when generic automatic sizing suggests 500 A; verify its time-current curve and interrupt rating. Longer runs require parallel conductors that this example does not validate. AC wiring and hybrid load support require separate design. Manufacturer installation manual
Edit this wiring exampleCable 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.
1 m one way
12 V system
- Wire
- 120 mm² · 4/0 AWG
- Example fuse
- 400 A
- Design current
- 400 A
- Voltage drop
- 1.0%
Sized against ABYC E-11. The design current is the part's continuous draw. 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.
12 V battery example for the original MSH3012RV. The manual specifies 400 A time-delay protection and at least 4/0 AWG (107.2 mm²) per polarity up to 5 ft / 1.524 m one way. The 1 m main conductors and 0.3 m disconnect link stay within that limit; the planner can choose larger wire for its conservative current/headroom assumptions. The 400 A DC value is maximum continuous input at low battery voltage, not typical draw at 12 V. Use the manual's 400 A fuse even when generic automatic sizing suggests 500 A; verify its time-current curve and interrupt rating. Longer runs require parallel conductors that this example does not validate. AC wiring and hybrid load support require separate design. Manufacturer installation manual
Supporting parts
- 2 m total of 120 mm² (4/0 AWG) marine cable
- Terminations for 120 mm² cable, matched to the equipment's screw terminals, leads or studs
- 400 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. 64-0089 Rev E, April 2023; original MSH3012RV), checked 2026-10-19. Manufacturer documentation →
Which Magnum inverter/charger is covered?
The original MSH3012RV connects a 12 V battery bank to 120 V, 60 Hz AC. The manufacturer's specifications, printed page 49, give 3000 VA inverter output, 125 A charging and 400 A maximum continuous DC input. The DC figure is a worst-case design value, not typical consumption. The manual gives AC surge ratings but no directly usable DC surge current; the catalog leaves DC surge unspecified.
What does the DC installation require?
Tables 2-1 and 2-2, printed pages 14–15, specify 400 A time-delay protection and 4/0 AWG (107.2 mm²) per polarity for runs up to 5 ft / 1.524 m one way. From 5 to 10 ft, each polarity requires two 4/0 AWG conductors. Longer runs are not recommended. The single-conductor calculation does not validate the parallel arrangement; keep the inverter close to the bank and review the manual before installation.
Use the manufacturer's 400 A protection for rated operation even if the generic automatic calculation proposes a larger fuse. A manual wire reduction or protection above the catalog's 400 A requirement is flagged. Choose the fuse's DC interrupt rating from the actual battery fault-current evidence; the manual recommends Class T or equivalent. Battery capacity alone does not establish discharge capability or charge acceptance.
How do the two AC legs work?
HOT 1 IN supplies the charger. HOT 2 IN provides the second pass-through leg and cannot independently charge the battery. Both input legs must come from the same source with the phase relationship specified in Table 2-3, printed page 22.
Standby operation permits 60 A on HOT 1 OUT with load support and 50 A on HOT 2 OUT. Battery-only operation shares 25 A total between the two outputs on the same 120 V phase, so it does not supply 240 V between them. The planner shows terminal ratings and separate charging/inverting states; it does not simulate hybrid load sharing, AC phase relationships or output allocation.
The abbreviated terminal diagram omits protective-earth connections, communication ports and neutral-to-ground switching. Follow the manual for AC breakers, grounding, GFCI compatibility, battery settings and commissioning.
Technical reference
Specifications and terminal map.
Check the model, ratings and connection points against your own unit before choosing installation hardware.
Catalog specification
12 V pure sine inverter/charger with 3000 VA / 25 A total inverter output at 120 V, 60 Hz and 125 A battery charging. Two 50 A AC inputs share a neutral; only HOT 1 supplies the charger. Split-phase pass-through and hybrid load support need separate AC design. The 400 A DC draw is the manufacturer's maximum continuous input, not typical consumption; DC surge is unspecified. Follow the manual's 400 A time-delay battery protection and cable-length limits. AC grounding and neutral switching are not modeled.
- Nominal voltage
- 12 V
- Compatible systems
- 12 V
- Rated power
- 3,000 W
- Continuous draw
- 400 A
- Rated output
- 125 A
Terminal map
HOT 1 IN supplies charging; HOT 2 IN is the second pass-through leg. A shared input neutral does not make HOT 2 a charging input. Battery-only operation shares 25 A total at 120 V across both output legs, with no 240 V between them. AC terminals are left disconnected; protective earth, neutral-ground switching and RV-C/control ports are omitted. DC surge current is not published.
HOT 1 IN
neutral · input
HOT 2 IN
neutral · input
NEUT IN
neutral · input
DC +
positive · input
DC −
negative · input
HOT 1 OUT
neutral · output
HOT 2 OUT
neutral · output
NEUT OUT
neutral · 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.
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