Split charge leakage?

Hi,

I have a split charge system operated by solenoid on the positive wires with negatives of main and leisure batteries permanently connected to vehicle chassis.

All auxiliary wiring is taken from the leisure battery via a fused cable to relevant smaller fused distribution points around vehicle.

All original wiring remains connected to main battery.

The situation as I look at it now with engine off and live wires disconnected from solenoid, is:
Main battery 12.5v
Leisure battery 13.0v

Turning on dipped lights drops the voltages to:
Main battery 12.1v
Leisure battery 12.8v

Turn off the lights and voltages will return to original readings.

Disconnect the leisure battery earth and the above process will result in leisure battery reading not being affected, as the battery is effectively removed from the system completely.

The question is then, with the solenoid not being engaged, why am I seeing a voltage drop on the leisure battery when turning on the lights (same effect with indicators, etc)??

My only thought using school boy physics is to do with electron flow rather than current flow causing this. Any enlightenment would be appreciated....

Thanks
Richard

Depends where you are sensing the voltage, if the volt drop on the vehicle side negative also includes the leisure battery negative, you'll get a false reading.

Check at the battery terminals only for each reading.

Peter

I'm taking the reading from voltmeter connected to individual live but shared earth. Will have a go direct from battery tomorrow and see....

Well I couldn't wait..... Just been out and tried and you're absolutely right. Time for a re-wire of dash voltmeters then.

What's the reason for this false reading?

Volt drop in the negative cable when the lights are on, being a shared connection it affects both meters.

Peter

google potential difference

Rewired with new switch to support additional negative connection and works a treat now, thanks chaps.