We have a 2022 Kia Niro EX EV (a US model) that we bought in April of 2022. Recently, starting in January of 2024, the 12V auxiliary battery (a T4-DL with 470 CCA and a 70 minute reserve capacity) has been running down often in less than 48 hours. Our mechanic hasn't been too helpful so I'm trying to get a picture of how the 12V system operates so I can start troubleshooting it.
According to the Kia manual "the auxiliary battery is automatically charged when the vehicle is in the ready mode or the high-voltage battery is being charged." The car is usually plugged in to a Level 2 charger (a Grizzl-e Smart).
The manual also discusses a feature called 12 V Aux. Battery Saver+ that "...monitors the charging status of the 12 V auxiliary battery. If the auxiliary battery is low, the main high voltage battery charges the auxiliary battery." The manual says that this system is on by default, but so far I haven't found a way to confirm this.
All of this suggests to me that the car should be maintaining the charge of the 12 V battery with little or no human intervention -- and that seemed to be the case for the first 21 months we owned the car.
I'm not sure if / how it could be relevant (and the mechanic flat out dismisses it) but, early in January I did an update on the informatics system. My impression, from Kia, before the update was that it was primarily an update of the navigation system and its maps -- but it did add an option to limit the negotiated charging rate. We had no problem with the 12 V battery before the update.
I'd appreciate pointers to information on how the 12 V auxiliary battery charging system is supposed to work and any suggestions for troubleshooting.
