I’m attempting to accomplish leisure battery to starter battery charging in my van using components that I already have on hand. Please take a look at this diagram and give me your thoughts if you think it’s acceptable and would work. I understand the graphic says converter and not charger. It’s depicted in the charger manual that way for some reason.
The 7 amp Bluesmart AC charger positive and the L/H pin remote wire would run through a 20 amp rated DPDT on-off-on rocker switch. It acts like a lock out so that only one of the devices can operate at a time. The Multiplus would need to be inverting or hooked up to shore power for the Bluesmart to be on.
I think the system would work as shown. However, it is a little inefficient taking your leisure battery DC, turning it into ac and then back into DC.
If your leisure and starter batteries are the same voltage why note use the Multiplus trickle charger function which goes from DC input, you can add a switch. You would need to add a fuse into the wire at the starter battery. Multiplus trickle charge explained here.
My FAQ discusses the lithium to lead acid issue in more detail with the pros and cons. If your batteries are not Victron and have an inbuilt BMS with low voltage discharge shutdown protection then you can be OK.
