What is split charging?

What is split charging?

Split Charging

Split charging is the term used to describe charging of the vehicle battery and the leisure battery at the same time from a charging source. On motorhomes and caravans the charging source would be the vehicle alternator which is in turn powered by the engine.

How Sargent PSU's split charge

Sargent power supply units (PSU) have a built-in split charge system. For this to work Sargent power supply unit (PSU) would need a connection to the vehicle battery, the leisure battery and also an engine run signal.

When the engine run signal is detected the internal split charge relay is energised and the two batteries are connected together so they both receive charge from the vehicle alternator.

Charging would only occur if the power supply unit (PSU) detected an engine run signal. If no engine run signal is detected this would mean no charging source is present and these connections would be electrically separated, ensuring that one battery does not draw current from the other.

Why do the batteries need to be separated when there not being split charged?

It is important to ensure that the vehicle battery is isolated from the leisure battery so you don’t flatten the vehicle battery and the engine can always be started, but you also don't want the leisure battery to be drawn upon when starting the engine because leisure batteries are not designed for high current output over short periods of time and they can be damaged.

Engine run signal or switched ignition, what's the difference?

Engine run signal

An engine run signal would give you +12V when the engine is running and 0V when the engine is off.

Switched ignition signal

A switched ignition would give you +12V with the ignition on and the engine is not running and 0V when the ignition was off.

It is important to find an engine run signal and NOT a switched ignition because if you find a switched ignition signal the split charge relay will engage and both batteries will be connected together during engine cranking which can damage the leisure battery. 

What if I can't find an engine run signal?

If you can’t find an engine run signal you can use a switched ignition signal but you would also need to use a voltage sensing relay (VSR).

Please click the link to find out more:  I can’t find an engine run signal, what can I do?

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