i recently ran into something similar myself on my late Husband's 2021 Ram 1500 Warlock. The reading on the dash was fluctuating between 13 and 12 Volts while it was running. Since it was the original battery, i KNEW that it needed replaced. To make a long story short, i went to Advance and had them run an Amperage Draw Test on it instead of a voltage test. It should have read 750 or higher; mine was reading TWENTY EIGHT! Yeah. was lucky that it died in my driveway and i was able to take the battery to exchange it since it didn't have anything in it left to crank, even after having it on charge overnight. Came home, put the new battery in, it's been reading at a solid steady 14 Volts on the dash while running. Ya learn something new every day. i should be good for another 4 years (that's the warranty that came with the battery). God is so GOOD!