Inverter & chargers
MultiPlus-II 2x120V – The One-Box Solution for North American 50A Split-Phase Power,PMP122305100
MultiPlus-II 2x120V – The One-Box Solution for North American 50A Split-Phase Power,PMP122305100
About this product
Most inverter/chargers on the market solve one problem: they convert DC to AC. The MultiPlus-II 2x120V solves a different one. It addresses the specific challenge of a North American 50A 120/240V split-phase distribution panel – a system that no standard single-input inverter can properly serve.
The Split-Phase Problem
A 50A RV or boat distribution panel has two separate 120V legs (L1 and L2), each rated for up to 50A. In a typical RV, these legs are not there to provide 240V. They distribute independent 120V loads across two circuits for load balancing – air conditioning on one leg, the microwave and outlets on the other. When shore power is present, both legs are live, and everything works.
The moment shore power disappears, the problem begins. A standard inverter/charger has one AC input and one AC output. It can only energize one leg of the panel. The other side of the distribution panel goes dark. Half your outlets, one air conditioner, and anything else wired to the unpowered leg simply stop working. To cover both legs, you need two inverters, an autotransformer, or a rewiring project.
The MultiPlus-II 2x120V eliminates all of that.
One Unit, Both Legs, Every Scenario
The MultiPlus-II 2x120V has two AC inputs and two AC outputs. When connected to split-phase 120/240V shore power, it passes through both lines at full 50A capacity. When connected to a single-phase 120V source – a 30A pedestal, a 15A household outlet, or a dogbone adapter – the L1 input accepts incoming power and the unit internally combines the L1 and L2 outputs, delivering 120V single-phase to both sides of the panel.
The critical difference is what happens in inverter mode. When no AC source is available, the MultiPlus-II 2x120V connects L1 and L2 together internally and feeds both legs from the battery bank. Both sides of the distribution panel remain energized. Users running this unit in fifth-wheel applications consistently cite this as the defining advantage: the load balancing across the entire panel in inverter mode is the key feature.
240V Loads and the Deliberate Limitation
The unit passes through true 240V when connected to split-phase shore power. However, 240V is not available in inverter mode. This means a 240V water heater or a 240V air conditioning unit will not start when running from battery alone.
This is not a shortcoming. It is a protective design. A 240V load draws power from both legs simultaneously, and a 3000VA inverter cannot sustain that kind of draw for long. Preventing these loads from starting in inverter mode protects both the battery bank and the inverter itself. Loads that must run on battery – refrigerators, outlets, 120V air conditioners, lighting, electronics – are all wired to individual legs and operate normally.
PowerAssist and the Single-Phase Boost
PowerAssist in the MultiPlus-II 2x120V operates on the L1 input only. When connected to a single-phase source, the unit boosts the incoming power with battery energy to handle peak loads. Plug into a weak 30A pedestal while running an air conditioner and a microwave, and the inverter supplements the shore supply instead of tripping the breaker. When the load drops, the charger recovers the battery.
In split-phase mode, PowerAssist works on L1. L2 is passed through directly. For RV users who primarily connect to 30A or single-phase sources, this covers the vast majority of real-world scenarios.
Transfer Speed and the L2 Nuance
The L1 output transfers to inverter power in less than 18 milliseconds, fast enough to keep computers and sensitive electronics running without interruption. The L2 output transfer time is longer – approximately 40 milliseconds – because it relies on a separate relay. This is still fast enough for most equipment, but the distinction matters for highly sensitive loads. In practice, users report no noticeable disruption when switching between shore and inverter power across the entire panel.
The 50A Transfer Switch and Full System Coverage
The built-in transfer switch is rated at 50A per leg. This means the unit can pass through the full 50A shore connection to the distribution panel without any current limitation on either leg. For a 50A RV running both air conditioners, a residential refrigerator, a microwave, and the usual complement of outlets, the MultiPlus-II 2x120V handles the entire load without requiring a sub-panel or load-shedding strategy.
Practical Installation Notes
Wiring the MultiPlus-II 2x120V into an existing RV that previously had a single-leg inverter requires planning. If the goal is to power the entire distribution panel from the inverter, the original inverter loop must be removed and the unit wired between the shore inlet and the main panel. This typically involves running 6/3 or 6/4 cable from the transfer switch to the inverter input and from the inverter output to the main breaker panel.
Users who have completed this installation report that the result justifies the effort. One owner of a 2020 Tiffin Open Road replaced a Magnum 2000VA inverter – which could barely run the microwave – with a MultiPlus-II 2x120V and now powers the entire coach, including air conditioning, from the inverter.
Parallel Configuration for Higher Capacity
A single MultiPlus-II 2x120V delivers 3000VA continuous output. In a 50A RV with two air conditioners and a residential refrigerator, 3000VA may not be sufficient to run everything simultaneously on battery. In these cases, two units can be paralleled for 6000VA total output. Users running dual 24V MultiPlus-II 2x120 units in parallel report seamless power management and full panel coverage in inverter mode.
For systems that do not require 240V loads – which is the majority of North American RVs – two paralleled MultiPlus-II 2x120V units provide more usable power than a single larger inverter, because both legs of the panel remain live at all times.
Battery Charging
The 12V model delivers 120A of charging current; the 24V model delivers 70A. Combined with adaptive four-stage charging and a battery temperature sensor, the MultiPlus-II 2x120V recovers a deeply discharged lithium or lead-acid bank efficiently during generator runs or shore connections.
Remote Monitoring
When paired with a Cerbo GX or Ekrano GX, the MultiPlus-II 2x120V can be monitored and controlled remotely via the VRM portal. Users running this configuration report that they can adjust settings, monitor power flow, and even auto-start a backup generator from anywhere in the world.
Specifications
MultiPlus-II 2x120 V | 12/3000/120-50 | 12/4k/160-50 | 24/3000/70-50 |
PowerControl &PowerAssist | Yes (on L1 input) | ||
Transfer switch | 50 A | ||
Maximum AC input current | 50A (each leg) | ||
INVERTER | |||
DC Input voltage range | 9,5-17V | 9,5-17V | 19-33V |
Output when in inverter mode | Output voltage:120VAC±2% Frequency:60Hz±0,1% | ||
Cont.output power at 25C/77℉(2) | 3000 VA |
| 3000VA |
Cont. output power at 25°C/77℉ | 2400 W | 3,4 kW | 2400W |
Cont. output power at 40C/104F | 2200W | 3,1 kW | 2200 W |
Cont. output power at 65°C/150F | 1700 W | 2,4 kW | 1700 W |
Time limited power 1 (cold start) |
| 4,0 kW/1h |
|
Time limited power 2(cold start) |
| 4,5 kW/30min |
|
Peak power | 5500 W | 6kW/2s | 5500W |
Maximum efficiency | 93% | 93% | 94% |
Zero load power | 15W | 18W | 11W |
Zero load power in AES mode | 10W | 11W | 8W |
Zero load power in Search mode | 4W | 4W | 4W |
CHARGER | |||
AC Input | Split phase: 180-280VAC55-65Hz | ||
Charge voltage 'absorption' | 14,4V | 14,4V | 28,8V |
Charge voltage 'float' | 13,8V | 13,8V | 27,6V |
Storage mode | 13,2V | 13,2V | 26,4V |
Maximum battery charge current (3) | 120A | 160A | 70A |
Battery temperature sensor |
| Yes | |
GENERAL | |||
Auxiliary output(4) | 50 A (each leg) See note 7 | ||
External AC current sensor (optional) | 100 A | ||
Programmable relay (5) | Yes | ||
Protection(1) | a- g | ||
VE.Bus communication port | For parallel and three phase operation, remote monitoring and system integration | ||
General purpose com.Port(6) | Yes, 2x | ||
Remote on-off | Yes | ||
Operating temperature range | -40 to +65℃(-40-150F) Fan assisted cooling | ||
Humidity (non-condensing) | max 95% | ||
ENCLOSURE | |||
Material & Colour | Steel, blue RAL 5012 | ||
Protection category | IP22 | ||
Battery-connection | 2x2 M8 bolts | 2x2 M8 bolts | 2 M8 bolts |
120/240 VAC-connection | Screw terminals 21 mm2 (4 AWG) | ||
Weight | 22kg (48 lb) | 25kg (55 lb) | 22kg (48 lb) |
Dimensions (hxwxd) | 578x 275x 148 mm | 650 x 275x165 mm | 578x 275x148 mm |
STANDARDS | |||
Safety | EN-IEC 60335-1,EN-IEC 60335-2-29,UL 458 | ||
Emission, Immunity | EN 55014-1,EN 55014-2 | ||
1) Protection key: | 2) Non-linear load,crest factor 3:1 | ||
Product Dimension Drawing
The Bottom Line
The MultiPlus-II 2x120V is not a general-purpose inverter/charger with an extra feature bolted on. It is a purpose-built solution for the North American 50A split-phase environment, designed to keep both legs of the distribution panel live in every scenario – shore power, generator, single-phase 120V, or pure inverter operation. For 50A RVs, large boats, and any application where the entire electrical panel must remain energized regardless of power source, it is the most direct and complete answer available.
Tags：
MultiPlus-II 2x120V
MultiPlus-II
MultiPlus-II GX
