Charging leisure & vehicle battery on mains

One of the very fortunate few being out in my van - Spanish border closed the day I reached it - holed up in a small town in SouthWest France. Question: When connected to mains electric the leisure battery alone charges due to the split charging relay being a one-way street. Would bridging leisure and vehicle battery with high grade jump leads be  stupid?

Anyhow keep safe everyone.

If all you want to do is keep the starter battery topped up, you do not need "high Grade Jump leads" as all you need to do is to pass a few amps (at most).

Don't try and start the vehicle with the batteries connected and you will be all right.

Post deleted, it was a duplicate due to finger trouble!

Thanks for super prompt reply. HaHa it's just that I have my commercial jump leads on board. Really I'm worried about any effect on alternator - I only understand dynamo tech! As it happens I carry a 'loose' spare battery and I charged that up via jump leads from leisure battery last week but clearly not quite the same

Is it fair to assume that the Duetto is on a Mk5 with manual gearbox?

If the leisure battery on the Duetto LE is really just another engine starter battery then linking them together temporarily should not be an issue at all, though you will obviously have to be a bit careful if they are in very different states of charge, as there will be a big spark when you connect (and, possibly, when you disconnect depending on how you do it) so you need to keep the batteries well ventilated to minimise any risk of a hydrogen explosion.

If the leisure battery is a proper (expensive) leisure battery then it would be wise not to do it if the state of the starter battery is very low, as you may damage the leisure battery.

In the longer term, an easy fix would be to make split charging a two-way street, using a VSR such as this, which is almost a straight drop-in replacement for the split charge relay:

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When I did it on the Trooper, the only things that needed changing were to swap two Lucar connectors for similar ring connectors.

Thanks for that Roopert. The relay upgrade looks interesting and I will look further when home. Good advice about large disparity of battery charge. Thanks.

Keep safe.

Is it fair to assume that the Duetto is on a Mk5 with manual gearbox?

Yes 2.5 turbo. Standard wet leisure battery.

Ok - I only ask because the battery setup from the Ford factory with an auto box is completely different! But that's of no interest to you.