Wiring two battery chemistries with one charger?

[Photobug]

My power box is going to be powered by a Relion 60ah battery. As I am building it now it contains a 100/20 Victron solar charger and an inverter. Eventually, it will also have a Victron AC battery charger. My goal is to have this be a portable battery box that is self-sufficient but also a source to charge the "house" FLA batteries on a truck and a boat. Initially, I was thinking of adding a dual battery switch to the box to direct the solar charger to either the internal "box" battery or the output of the box "house" battery.

Some questions/concerns:

A dual battery switch is a single pole double throw switch. Would a battery switch sending positive current to the "box" or the "house" battery with a common negative going to both the house and box battery, effectively allow me to switch the output from one battery to the other? I will use the Victron app to switch the charging profile based on the battery being charged?

Would a DPDT relay throw allow me to use a single switch to control both a solar or an AC charger to switch between power "box" or "house" batteries?

 

[luthj]

That's what a switch does, there is no need to switch the ground in that application. Assuming both batteries are okay with the ~14-14.4V charge voltage, there is not reason they cannot be parallel for charging purposes. The Lithium battery should have the charge terminated instead of having the absorb held though, so you would want to address getting the lead to true 100%, as the early termination for the lithium battery would leave the lead battery at around the 90-95% SOC range. The lithium shouldn't be floated either, though a lower float voltage is generally acceptable.

 

[Photobug]

That's what a switch does, there is no need to switch the ground in that application. Assuming both batteries are okay with the ~14-14.4V charge voltage, there is not reason they cannot be parallel for charging purposes.

Thanks it's as I thought.
My current solar charger is programable for battery chemistry. I would like to be able to charge them individually to make sure they are charged optimally if time allows, just to make sure the Lead Acid battery gets through the absorption phase on occasion.

 

[JackW]

I just bought a Redarc BCDC 1225D which does exactly what you want. I'm going to combine it with a Redarc SBI12 solenoid switch per this diagram. The Redarc supposedly can handle different battery chemistry automatically depending on how its wired up.

https://www.redarc.com.au/Content/Images/uploaded/Handy%20Hints/Dual%20Input%20Ultimate%20Dual%20Battery%20Setup.pdf