12V Battery Issues?

Unfortunately reliability is not what you will get with the Gen 5 Prius Prime 12v Battery. Toyota engineers chose to implement a 12v Battery Management System that puts vehicle mileage efficiency first, and 12v battery reliability second. The stock 12v in the 2024 Prius Prime XSE is not a strong battery. As you search thru the posts here you will find that many owners have replaced the original battery either under warranty or at their own cost. After replacement the new battery soon becomes somewhat unreliable if the car is not driven daily, and with time becomes unreliable even if the battery is not driven daily. The new battery is still charged IAW the Battery Management System toyota engineers chose to provide with the car.
In time you will get a battery maintainer device and maintain the battery periodically (either weekly or monthly) to get the reliability you want. Or you will continue to deal with Toyota dealership and your warranty to replace the battery more often than you would expect.
Sad story indeed !

 

One thing you can do to help the battery perform more reliably is to never use the cars ACC mode. Put your foot on the brake and push the start button every time you are in the car. Don't listen to the radio or use any accessories on the car unless the car is in the Ready mode.

 

Not my experience. I've had my SE since March 24 without any battery issues. I've occasionally not used the cars for a few days, most recently it sat for16 days without losing any charge. I typically charge the "big battery" overnight.