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MultiPlus-II 12V/24V 3kVA 2x120V

2. Description

In this section:

2.1. 120/240V input and output, or 120V input and output (always 120V output when in inverter mode)

The AC input can be supplied from a split-phase 120/240V source or a single-phase 120V source.

When an AC source is available, the MultiPlus will feed through the AC to its output. The output will therefore mirror the AC input.

The inverter/charger connects to the neutral and the preferred input line (L1). The power needed to charge the batteries will therefore be drawn from L1 (see fig )

The MultiPlus switches to inverter operation when no AC source is available. The inverter output is 120V single phase. In invert mode, the MultiPlus connects both output lines (L1 and L2) together to provide 120VAC to loads on either line.

Any 240V loads will therefore be supplied only when the MultiPlus is supplied by a split-phase AC source. This prevents heavy loads such as water heaters or 240V air conditioners from discharging the battery.

240V loads should be connected between L1 and L2 which could be either ACout1 or ACout2. There will be 240V between them when the unit is connected to a split-phase input and 0V otherwise (single phase grid or inverter mode). The voltage L1-N and L2-N will be 120V regardless of single or split-phase input. This can be better understood with the addition of the power flow diagrams.

2.2. Other features

Automatic and uninterruptible switching (AC out 1)

In the event of a supply failure or when the generating set is switched off, the MultiPlus-II will switch over to inverter operation and take over the supply of the connected devices. The transfer time of the L1 output is less than 18 milliseconds so that computers and other electronic equipment will continue to operate without disruption.

The transfer time of the L2 output is longer: approximately 40 milliseconds.

Auxiliary output (AC out 2)

The second (auxiliary) output is live only when AC is available on the input of the MultiPlus. Loads that should not discharge the battery can be connected to this output. Please enter “AC-out-2” in the search box on our website and find the latest information about other applications.

Three-phase capability

Three units can be configured for three-phase output. Up to 6 sets of three units can be parallel connected. In multi-phase setups, L2 the output is disabled for all units.

PowerControl – maximum use of limited AC power

A maximum grid or generator current can be set. The MultiPlus will then take account of other AC loads and use whatever is extra for battery charging, thus preventing the generator or grid from being overloaded (PowerControl function).

PowerAssist – Extended use of a generator or shore current: the MultiPlus-II “co-supply” feature

PowerAssist takes the principle of PowerControl to a further dimension. Where peak power is so often required only for a limited period, the MultiPlus-II will compensate insufficient generator, shore or grid power with power from the battery. When the load reduces, the spare power is used to recharge the battery (available on L1 input only).

Programmable relay

The MultiPlus is equipped with a programmable relay. The relay can be programmed for different applications, for example as a starter relay for a generator.

External current transformer (optional)

External current transformer option to implement PowerControl and PowerAssist with external current sensing.

Programmable analog/digital input/output ports (Aux in 1 and Aux in 2, see appendix)

The MultiPlus is equipped with 2 analog/digital input/output ports. These ports can be used for several purposes. One application is communication with the BMS of a lithium-ion battery.

2.3. Battery charger

2.3.1. Lead-acid batteries

Adaptive 4-stage charge algorithm: bulk – absorption – float – storage

The microprocessor-driven adaptive battery management system can be adjusted for various types of batteries. The adaptive function automatically adapts the charging process to battery use.

The right amount of charge: variable absorption time

In the event of slight battery discharge, absorption is kept short to prevent overcharging and excessive gas formation. After deep discharging, the absorption time is automatically extended in order to fully charge the battery.

Preventing damage due to excessive gassing: the BatterySafe mode

If, in order to quickly charge a battery, a high charge current in combination with a high absorption voltage has been chosen, damage due to excessive gassing will be prevented by automatically limiting the rate of voltage increase once the gassing voltage has been reached.

Less maintenance and aging when the battery is not in use: the Storage mode

The Storage mode kicks in whenever the battery has not been subjected to discharge during 24 hours. In the Storage mode float voltage is reduced to 2,2V/cell (13,2V for 12V battery) to minimise gassing and corrosion of the positive plates. Once a week the voltage is raised back to the absorption level to ‘equalize’ the battery. This feature prevents stratification of the electrolyte and sulphation, a major cause of early battery failure.

Battery voltage sense: the correct charge voltage

Voltage loss due to cable resistance can be compensated by using the voltage sense facility to measure voltage directly on the DC bus or on the battery terminals.

Battery voltage and temperature compensation

The temperature sensor (supplied with the product) serves to reduce charging voltage when battery temperature rises. This is particularly important for maintenance-free batteries, which could otherwise dry out by overcharging.

Two DC outputs for charging two batteries

The main DC terminal can supply the full output current. The second output, intended for charging a starter battery, is limited to 4A and has a slightly lower output voltage (12V and 24V models only).

2.3.2. Victron Lithium Battery 12.8V & 25.6V Smart

Victron LiFePO4 Smart batteries Use the VE.Bus BMS

2.3.3. Other Li-ion batteries

Please see https://www.victronenergy.com/live/battery_compatibility:start

2.3.4. More on batteries and battery charging

Our book ‘Energy Unlimited’ offers further information on batteries and battery charging, and is available free of charge on our website (see www.victronenergy.com → Support & Downloads → Technical Information). For more information on adaptive charging, please also refer to the Technical Information on our website.