Idiotoc question, van battery flat whilst plugged in to mains.

[roadtripper]

It can make sense yes but it tends to be a feature of more advanced installs.

The installed way of doing it is to have a dual charger unit, or you can get trickle charge diodes.

Changing the whole charger would probably be very disruptive for you and not worth it.

The trickle charge approach is mostly to stop the self discharge of the starter battery if you use the van less frequently but have solar/EHU when parked at home, and that doesn't sound like how you use your van but they are small and you may be able to fit one.

A third DIY way you could do right now is to get a simple maintenance charger from someone like CTEK or NoCo and a cigarette lighter adapter. Then you plug the charger into a van mains socket when you are on EHU and plug the other end into the permanent live dash 12v socket.

Several threads on all three approaches around the forum.

 

[Graham Jones]

the 3rd DIY works well for me. Also allows me the choice of which battery top up.

 

[Salty Spuds]

Wouldn't it make sense to be able to charge the main (engine) battery when hooked up to the mains in the same way as the leisure battery ? @roadtrippers manual pic explains the differences for each switch selection but no mention of charging the main battery, I'm assuming newer panels must be able to do this?

It would, and there are devices & systems available to do exactly that. I have an Ablemail AMT12 doing the very same. But these are unidirectional & only allow current one way. They charge the van battery, but don’t allow current back to the domestic side.