I bought a new 2019 Kia Forte last year, from the day I received it, its battery (lead-acid AGM) read a slightly low open voltage of around 12.45V. I figured out the car must have been driven on the dealer's lot for small distances therefore never got the chance to be fully charged.
Hooking it up to my own battery maintainer, I charged it as to around 12.7V which seems to be the norm for AGM batteries.
However, after driving a couple times for 100km+, I rechecked it and was dismayed to find the voltage near 12.3!
Over the course of the year, I found out that the battery likes to stay at 12.3, no matter what you do. It doesn't seem to fall lower, but without manual charging, it never gets higher.
According to my knowledge, 12.3 is not a good voltage level for a lead-acid battery to be at perpetually, it'll definitely lead to early battery failure. Right now I'm charging it every once in a while to keep to higher, but obviously this isn't a solution to the problem.
My nearest dealer is quite far, and they're probably simply gonna recommend changing the battery, which I know isn't going to work.
What could be the problem here? Electric leaks seems a bit unlikely since the battery level doesn't drop without stopping. Could it be the alternator is not performing correctly? If I were to take it to the dealer, how should I explain the situation to them?