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# How should I connect a temperature sensor to the battery?

A temperature sensor must always be connected to the negative pole of the battery.

When multiple batteries are connected in parallel and / or series, the temperature sensor is only connected to the negative pole from which the battery cable departs.

If multiple devices (Multi, Quattro, ...) are connected in parallel or 3-phase, only one temperature sensor is connected to the master unit.

# Why are batteries connected in series?

A connection in series is been made when the power, supplied to or taken from the batteries, becomes very high and resistance of the wiring could be a problem. For the correct functioning of the batteries connected in series it is very important that performances of the connected batteries are equal. This means the batteries have to be taken into service as a "set" of the same age and type. Mixing battery types causes trouble because the smaller one is overcharged and the bigger one is starved and will lose capacity.

For instance:

2 batteries 12V / 120Ah in series become a 24V / 120Ah system.

Schematic representation

# Why are batteries connected in parallel?

When making a connection in parallel, special attention is needed for the cabling used. It is of the utmost importance that all the wires from terminal to the central conductor are of the same length. A difference in lenght means a difference in resistance which results in an undercharged battery on one end of the chain and an overcharged battery on the other end.

For instance:

2 batteries 12V / 120Ah in parallel become a 12V / 240Ah system.

Schematic representation

# Why are batteries connected in series/parallel?

With a series/parallel connection 2 x 2 batteries are first connected in series.Then these 2 groups are connected in parallel.

4 batteries of 12V / 120Ah become a system of 24V / 240Ah.

A very important but often forgotten part in a series/parallel connection is the so-called compensation cable.
This cable, mounted between the series strings, takes care of voltage differences over both strings by equalisation. In an ideal situation, with 100% identical batteries, this cable is currentless.

Schematic representation

# What section should my battery cables have?

The wiring between battery and charger or inverter has to match the highest current possible. Thin cables get hot on high currents and cause a voltage loss. The voltage supplied to the battery is lower and charging takes more time.

The optimal diameter for the cable is:
charge or discharge current x 0,25 x metres cable

For example for a 50A charger with 2 metres of cable this is:
50 x 0,25 x 2 = 25mm².

When choosing between different standard diametres always take the thicker one.

This table gives an indication on the size of battery cables.

# What is the best charging currrent for my battery?

The best charging current lies between 10 and 20% of the C20 battery capacity. For a 12V 200Ah battery this is between 20A and 40A.

# Is temperature compensation important when charging batteries?

When charging batteries temperature of the battery and the environment is of importance.The gassing voltage and consequently the optimum absorption and float voltages are inversely proportional to temperature. This means that in case of a fixed charging voltage a cold battery will be insufficiently charged and a hot battery will be overcharged.
The charging voltage, as quoted by European battery manufacturers, applies at 20°C battery temperature and may be kept constant as long as the temperature of the battery remains reasonably constant (15°C to 25°C). Outside this temperature range temperature compensation is important, and must be implemented.

# What is the "Voltage Sense" feature on Victron Energy chargers?

The function "Voltage Sense" on the Victron Energy chargers compensates the voltage drop in the cables / fuses /connection points. The wires should go straight from the charger to the battery.

# How can I protect my installation (Phoenix Inverter / Multi / Quattro) with an earth leakage circuit breaker?

Inverters and Multi's are safety class I products (supplied with a ground terminal for safety purposes).
Its AC input and/or output terminals and/or grounding point on the outside of the product must be provided with an uninterruptable grounding point for safety purposes.

1. The Phoenix Inverter Compact has a free floating AC output. The grounding point located externally on the product must be used to ground the chassis. The neutral output wire must be connected to ground to ensure proper functioning of a GFCI (Ground Fault Circuit Interrupter).
2. Phoenix Multi / MultiPlus Compact / Quattro: the output neutral wire will automatically be bonded to the chassis&nbsp;when no external AC source is available (backfeed / safety relay open and product running in inverter mode). When an external AC source is provided, the ground relay opens before closure of the backfeed / safety relay. Once closed, the backfeed / safety relay ensures that the neutral to ground bond is provided by the external AC source. This is to ensure proper functioning of a GFCI to be installed in the AC output of the Multi/MultiPlus.
• In a fixed (for example terrestrial) installation an uninterrupted chassis ground may be provided by the AC input ground wire.
• In case of a mobile installation (connection to input AC with a shore power cord), the ground connection is lost when the shore power cord is unplugged. In this case the chassis of the product or the on - board section of the input ground wire must be connected to the frame (of the vehicle) or the ground plate or hull (of a boat).
• Marine applications: due to the potential for galvanic corrosion it is in general not acceptable to connect the shore side ground to the ground plate or hull of the boat. The proper and safe solution is to install an isolation transformer.

# Is it possible to put two (or more) inverters or Multi's in parallel?

YES, up to 5 Phoenix Inverter 3000VA can be connected in parallel to increase the output power. "Small" inverters do not have this feature and will be damaged when connecting&nbsp;an AC source to the output.

Multi's and Quatrro's have a "Power Assist" function and synchronize their output to the shore or generator output; in this way up to 6 units can be connected in parallel with an inverter power of 45kW/54kVA and a charge current of 420A.

This is only possible with the same types of units, different types can not be paralleled.

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