strange reading on voltmeters

[scottbott]

I hope this is not a stupid question but if it is I will apologise for it,I have fitted a battery under the rear seat to power my webasto heater,I have also fitted a Ctek charger into the RCD unit so when I hook up it automatically charges the battery,I have also fitted a dual USB /volt meter on the front panel of the rear seat running off the battery so I can see what is going on.The cigarette lighter in the front has been replaced with a digital voltmeter and two charging points so I can also see what is going on with the main battery,the query that I have is that when on hookup the reading on the rear voltmeter is the same as the front voltmeter even though they are not connected in any way!,am I charging both batteries at the same time?,I cannot see how,I can understand that when driving all three batteries will get charged and both voltmeters will read the same,any ideas?

[marlinowner]

If you have a voltage sensing split charge relay to charge leisure batteries when engine running, it may be triggered by the charger on hookup and connect the batteries together.

[Oldiebut goodie]

Possibly the previous owner has wired the cig lighter to the leisure (is the radio on the same wiring?) to plug something in whilst camping it up. If the fuse is still working / present in the fuse box that would be a no though. ( I would expect a dedicated fuse and cable if that was done)

[Oldiebut goodie]

If you have a voltage sensing split charge relay to charge leisure batteries when engine running, it may be triggered by the charger on hookup and connect the batteries together.

But the charger wouldn't cause the starter voltage to rise so couldn't trigger the relay. Relay stuck maybe though.

[lloydy]

If you have a voltage sensing split charge relay to charge leisure batteries when engine running, it may be triggered by the charger on hookup and connect the batteries together.

i reckon its this, my ctek charges the starter which wakes up my sterling charger which does the leisures

[scottbott]

is that ok?,if so that is a result,I will remove the lidl/aldi charger that I use when on hookup for the starter and leisure batteries,I do have an intelligent split charge relay which I fitted as no leisure battery on the van when I bought it,my radio is wired straight to the leisure battery not sure about the fag lighter I assume it is as standard