I suspect that you have something other than a battery problem. IIWY, I would do a careful check of all the wiring that is close to the batteries and alternator. Look for a loose wire, and pay particular attention to ground connections. If all is well, consider the alternator. If when the car is running, the voltage indicator shows 13.6 volts or better, it is probably not the alternator. Please tell us which battery that you replaced, ESS or main. This is a simplistic approach and YMMV.
2018 Touring L+
March 2018 Build