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Quattro-II 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 Quattro-II will feed through the AC to its output. The output will therefore mirror the AC input.

The Quattro-II connects to the neutral and the preferred input line (L1). The power needed to charge the batteries will therefore be drawn from L1.

The Quattro-II switches to inverter operation when no AC source is available. The inverter output is 120V single phase. In invert mode, the Quattro-II 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 Quattro-II 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 AC-out-1 or AC-out-2. 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 when looking at the power flow diagrams located in Appendix G, Power flow diagrams.

2.2. Boats, vehicles and other stand-alone applications

The basis of the Quattro-II is an extremely powerful sine inverter, battery charger and transfer switch in a compact casing.

Important features:

Two AC inputs; integrated switch-over system between shore voltage and generating set

The Quattro-II features two AC inputs (AC-in-1 and AC-in-2) for connecting two independent voltage sources. For example, two generator sets, or a mains supply and a generator set. The Quattro-II automatically selects the input where voltage is present.

If voltage is present on both inputs, the Quattro-II selects the AC-in-1 input, to which normally the generating set is connected.

Automatic and uninterruptible switching

In the event of a supply failure or when the generating set is switched off, the Quattro-II will switch over to inverter operation and take over the supply of the connected devices. This is done so quickly that the operation of computers and other electronic devices is not disturbed (Uninterruptible Power Supply or UPS functionality). This makes the Quattro-II highly suitable as an emergency power system in industrial and telecommunication applications.

Two AC outputs

Besides the usual uninterruptable output (AC-out-1), an auxiliary output (AC-out-2) is available that disconnects its load in the event of battery operation. Example: an electric boiler that is allowed to operate only if the genset is running or shore power is available. There are several applications for AC-out-2.

Please enter “AC-out-2” in the search box on our website and find the latest information about other applications.

Three phase capability

Up to 6 sets of three units can be parallel connected. Three units (or three sets of paralleled units) can be configured for three-phase output, to provide 43kW / 54kVA inverter power and more than 1260A (24V) charging capacity.

PowerControl – maximum use of limited AC power

The Quattro-II can supply a huge charging current. This implies heavy loading of the AC mains or generator. Therefore a maximum current can be set. The Quattro-II then takes other power users into account, and only uses 'surplus' current for charging purposes.

- Input AC-in-1, to which usually a generating set is connected, can be set to a fixed maximum, so that the generating set is never overloaded.

- Input AC-in-2 can also be set to a fixed maximum. In mobile applications (ships, vehicles), however, a variable setting by means of a Multi Control Panel will usually be selected. In this way the maximum current can be adapted to the available shore current in an extremely simple manner.

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

This feature takes the principle of PowerControl to a further dimension allowing the Quattro-II to supplement the capacity of the alternative source. Where peak power is often required only for a limited period, the Quattro-II will make sure that insufficient AC mains or generator power is immediately compensated for by power from the battery. When the load reduces, the spare power is used to recharge the battery.

Programmable relay

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

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

The Quattro-II 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

If Victron Lithium Smart batteries are used, use the VE.Bus BMS V2 or the Lynx Smart BMS.

2.3.3. Other lithium batteries

If other lithium batteries are used, follow this link for a list of compatible battery types and how to install and configure them:

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. It can be downloaded from:, or a hard copy can be ordered from:

For more information on adaptive charging, please refer to the technical paper: Adaptive charging, how it works.