I am doing more research, that is why I am asking here, where real technicians are…
Yes I know it is complex… but I want it to be somehow automated and redundant.
To be honest I did not think to isolate it, only fuses of course. But good point to use isolated DC - DC Charger in case of failure.
“…and also use the Orion with settings that will allow charging for the lithium if required.” -by this you mean charge by DC - DC in opposite direction, from AGM to Lithium when engine is running?
You have any advice for good model of battery status display for multiple AGM battery?
I think something like this will work. This system will isolate all 3 batteries. You can charge from the alternator or solar. If you want to charge the Lithium with an alternator you can disconnect the Anderson plugs and adjust the charge logic. If AGM 1 is low and unable to start the motor you can combine them manually with a switch. I can’t think of anything more simple. I would not use the Orion XS unless you want to fast charge the Lithium with the alternator. The AGM will only need a small charge current the 18 amp is fine and max solar output will around 40-45A max.
I have a less complex system in my RV. Solar charges the LiFePO4 using 2 x 150/35 MPPT. An Orion XS is powered by the LiFePO4 battery bank and charges a simple lead acid battery on the tongue of the RV at a programmed lower current than the maximum that the Orion XS is capable of. The lead acid battery is used to start the generator and run the tongue jack.
I have configured the Orion XS such that it does not look for an engine running signal. Essentially, it can charge the tongue battery at any time if there is sufficient voltage available from the LiFePO4 battery.
I haven’t tried or even researched it, but a Cerbo GX may be able to control some elements of the charging of the Orion XS. At the very least, the Cerbo GX can turn the Orion XS on/off using the remote switch.
Both solar charge controllers are connected to the “system” through the common busbars. Both batteries are also connected to the “system” through the common busbars. Each solar charge controller has its own set of panels.
Below is the Version 1 design diagram for that system. A subsequent version replaced the inverter and converters with a Victron Multiplus 12/3000.
