Adding two chargers in one pv array

[elias]

Merry Christmas to all !
Had anybody tried installing 2 mppt chargers ,  connected on the same pv array , for charging 2 separate batteries ?

[IslandAlchemy]

Why not just buy a dual MPPT controller?

[elias]

I have already 2 mppt.., is very tough for me mentally to buy a 3rd one , well if it is the only solution I will but I want to try

[SYJetzt]

Connecting 2 mppt's on one solar array won't work! Each MPPT has to be connected to a separate PV array.
I would go with one MPPT charger to the first battery and a B2B-Charger between the first and the sencond battery.

[elias]

Hmmm I understand , for one array one mppt . Thanks

[SYJetzt]

I assume you are speaking from the house (service) battery and the starter battery. There is no need to charge the starter battery from a solar panel. The starter batt will be charged by the alternator sufficiently.

[elias]

Not exactly ,I have one starter battery , one bank and recently one lifepo4 battery dedicated only to the 220v inverter  . The alternator splits with that Victron isolator (blue thing)the current to the starter and the lead acid battery bank . The mppt charges the lead acid . The new installed lifepo4 should be charged somehow too .
1. So a dc dc charger from the bank will be one solution but I would like some energy from the pv array .

[SYJetzt]

In this case a B2B charger will work fine. There are three key features to look for the charger:
1) Output of charger should provide a dedicated characteristic for charging lithium batteries.
2) Input of charger needs a detection circuit (wake up) to start charging, if there is energy available (from solar or alternator).
3) Sufficient charging power to bring the lithium battery up to full charge in time (this is depending on your energy demands drawn from your lithium batt/Inverter and the time when additional energy is available, no matter from which source )

For example a Victron Orion should do that job well, but there are other brands on the market too. 

To provide proper function a diligent installation and setup of the charger is key.

[SYJetzt]

forgot to mention: In this concept the existing house- and starter  battery remain unchanged. The new B2B will start charging only when additional power is available (from alternator and/or PV-array via mppt). So first your service batt (and starter batt) will be charged, and after the servicebattery is charged to full the lithium will be charged. So your service batt cannot be discharged unintentionally by the B2B-charger 

[elias]

Did some research last days and looks that your suggestion like Victron Orion is the most appropriate for the job . Can be regulated to start and stop at certain input voltages . Thanks