2024 Prius Prime dead battery

i guess we'll find out. the 12 volt on our last hycam was original at 10 years old when we traded for this one. same driving scenario. other than our once a year florida trip, it mostly sits.

 

There is no need for guesswork. You can hook up a BM2 battery monitor.

BM2 battery monitor on Amazon

 

not having any 12v problems with toyotas over the last 25 years allows me the luxury of sleeping well

 

But you didn’t own one with a 12-V-battery-management system until last year.

 

what has changed?

 

I think the older Toyotas did not have a 12-V-battery-management system with a battery sensor, and they kept the 12-V battery fully charged at all times as long as the car was driven every now and then.

The newer Toyotas with a 12-V-battery-management system with a battery sensor hardly charge the 12-V battery no matter how long or how often the car is driven. They try to keep it at around 80% SOC with minimal charging by using a very complicated charging algorithm. In fact, you could even be driving the car and still draining the 12-V battery.