I don’t know much about this, but we a 2020 2020 Kia Sedona with 36,000 miles, original battery. It had trouble starting the other day but I believed that was from an open door and light being left on. It has been driven about 2 hours since then. The 12.48v reading was right after I drove and turned car off. The morning reading was a cold 30F morning if that matters. I don’t know too much about cars so wondered it was worth replacing. Thank you
Either the battery is failing or you have a parasitic draw.
So from experience, Kia’s will sometimes keep the visor mirror light on after you shut the engine off even if you put the visor up. You need to close the little door on the mirror, to shut off the light then put the visor back up. The little light on will draw on your battery overnight.
Not saying that’s what’s going on but just as an example of the odd little things that can lead to a power draw without you even thinking about it. Turning the car off doesn’t always mean that everything inside also turns off.
Try unplugging all of the usb stuff and make sure all the lights are set to off and see if you’re still getting a lower voltage.