Help required to understand a wiring diagram

[Nick26]

I'm trying to get a better understanding of the 12V wiring system for my motorhome which is an Autocruise Starspirit, wiring diagram attached. I don't know what the purpose is of the "Split Charge Relay" showing in the TLH of the diagram. Is someone able to explain please and perhaps also tell me where I will find it physically.
Thanks in anticipation.

 

[mitzimad]

A split charge relay makes a connection between leisure and starting batteries when the engine is running to allow charging when you switch of the relay break s the circuitso you can only use what s in the leisure battery and allowing you to be able to start the van from a still full starter battery

 

[Nick26]

Thanks for your response mitzimad. Just to clarify though, I think you are telling me that whilst I am driving the alternator will be charging both vehicle and leisure batteries and when I switch off the ignition I will only be drawing power from leisure batteries when using habitation equipment e.g. lights, pumps, fans etc., is this correct?

 

[Bobby-gg]

Watch this

 

[pappajohn]

Got it in one Nick .
On older vehicles the split charge relay is nothing special.
It's usually a standard 30amp automotive relay.
On more modern vehicles it's usually part of the control panel/distribution console

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[TheBig1]

On the older autocruise, the split charge relay is near the battery positive terminal. Look for a fairly large wire with a fuse in it coming off the battery terminal and heading towards the bulkhead/firewall below the windscreen

 

[xsparks]

I thought that relay closed the step when the ignition is activated.

 

[Cush]

I thought that relay closed the step when the ignition is activated.

I thought that was done by the d+ signal wire to the step to tell the step that we’re about to drive off because the engine is running. Very happy to be corrected though.

 

[autorouter]

In the top left, the Alternator Field Circuit sends out a signal to show the engine is running, along that blue wire. It is usually called the D+ signal. It's the signal that turns off the red alternator light on the dashboard when the engine starts. It triggers the two relays, called the split charge relay and the fridge relay.

Power to the relays from the vehicle battery comes along the brown wire. Of the two relays, the one on the right is the split charge relay. When the engine is running, the relays are closed, so power flows through the leisure battery fuse, along the blue.brown wire. One branch goes to the leisure battery to charge it, the other branch goes to the PSU2007 power distribution box to all the habitation loads.

The other relay, the one on the left, sends 12V power along the red/yellow wire to the fridge 12V element, but only while the engine is running and the relay is closed. The fridge control board controls the switching of the 12V, 240V and gas to power the fridge. It is powered by the brown/yellow wire, which comes from the PSU2007 unit and is on all the time.

The fridge relay also sends the power and control signal along the red/yellow wire to automatically retract the step when the engine starts. You can check this because the step doesn't retract when the ignition key turns, but retracts when the engine starts.