question

If the 2 battery banks can share a common ground connection, then you can use an automatic charging relay that closes when the 1st bank charged is >13V (i.e. being charged). This will open when the charge voltage drops. Otherwise, you could use a high voltage relay driven by the PV to connect the 2 banks. There are a number of options, but I have not seen an MPPT charger with dual outputs!!

Thanks Miked, will the Automatic Charge relay allow the current to flow back from the bank with the higher voltage when the load is on & other bank drops below 12.4 (or a set voltage)? The reason I`m asking is that my charge controller (Victron 100/20) has the load terminals built in so when the load is on and one bank drops down to say below 12.4V will the relay allow/switch current flow from the battery to the charge controller?

Due to the above mentioned thought I`m thinking to simply install an isolating switch to charge up a bank at a time instead of an Automatic Charge relay...

Don`t know if I managed to explain my question correctly!?

Thanks,

Sam

You could use a Victron Dou. BlueSolar PWM Charge Controller (DUO) LCD&USB - Victron Energy

This depends a bit on the type of Automatic charge relay. As your MPPT has a load output, this can be set to connect when the primary voltage is high, and yes, current can flow both ways from the 'Load' battery to the 'Battery' terminals. You will need to program the load relay to achieve the desired result. When the voltage drops below your programmed threshold, the load switch will turn off. Installing an isolating switch or switches would be the simplest way to do this if the required charging of the 2nd bank is not frequent. If it is regular, then a relay would be worth the effort.

i have a mppt 75/15 smart solar charge controller.

can i use it for charging two batteries at the same time?

how should i connect them to do so?

thanks