I am just curious, why did you replace the two Optima batteries?
Did they discharge beyond their ability to recharge?
Are they ancient?
I ask because an Optima 6V Red Top should be good for between 8 & 10-years.
I did the same a few years back, but that was for a weekend when I needed to run he car.
I had left the ignition ON! EESCH!
My two charged up within a few days and the standard NAPA wet-cell 6V battery is now on the shelf awaiting my next screw-up.
I now have two Optima batteries in my battery box, but only one is hooked up and the other sits idle as a backup.
You might want to put them on a serious charger (NOCO Genius-10 – https://no.co/genius10)
Again, I am just curious.