Charging/split charge relay problem

[trevskoda]

I was thinking you'd simply leave your system exactly as it already is. You'd use the relay contacts on the Ebay unit to work in parallel with your dash switch.
The Ebay unit would monitor the charge current to the van battery and then when the current dropped to a specific level (which you can adjust) then the ebay unit relay would click in and bring in your HD relay to charge your les batt automatically. Because you'd leave the dash switch in place you can still get your emergency boost.

Yes would work, just a bit more wiring.

 

[Big Bill]

I have fittted two of these to Transit's with two engine batteries

You connect the charger's "battery input" to the engine batteries through a 50 Amp fuse and the 0v to a convenient earth.
You connect the "leisure battery" to the correct terminals with a 50 Amp fuse, the 0v on the leisure Battery need not be earthed. There is a 12 volt input which you connect to an ignition controlled switch and hey presto the unit charges the leisure battery correctly when driving.
You use the menu to tell it what type of leisure battery you have to make it charge correctly.

Another pair of terminals allow you to input charging from solar panels in series. The MaxPowerPointTracking [MPPT] then converts that High voltage power into 12 volts delivering as much as it can with the suns rays (up to 50 Amps) . It even does this while you drive down the road.
I put a high power rectifier between the leisure battery and the vehicle battery so that the solar power keeps both sets of batteries fully charged.
Keeping your batteries fully charged enhances their life, my last engine battery lasted 14 years and only died when my battery charged boiled it dry. A US motorhome with the 50Amp charger can eat batteries unless modified.