Good morning, all.

I considered myself extremely lucky on Monday afternoon to purchase a gently used 2015 ES 300h (with ~ 42,000 miles) from a private seller for $17,000. Prior to the purchase, the vehicle was inspected by a highly-rated local mechanic/shop and given a very clean bill of health.

Last evening, approximately 24 hours after the purchase, while sitting in the car playing with the settings for the navigation/display, the car lost power/shut off. I called AAA, and the kid that came out to take a look at the car diagnosed the issue as being a dead 12V battery (in the trunk of the car). It appears the current battery is the original 6-year-old OEM Panasonic battery. And, of course, given that the vehicle (apparently) will only take an OEM or Exide MX24 battery, he was unable to replace it last night.

Given that the car is in the process of being registered, it is currently stuck (literally and figuratively) in our garage until we receive the new registration sticker and plates in the mail from the DMV. They should arrive in ~ one week.

I was up all night reading and am at a loss -- anxious, nervous, frustrated, tired.

Given that I'm not a "car guy" and am somewhat distrusting of car dealerships, I'm not quite sure exactly where to start. Does it sound like the "simple" issue of replacing the 12V battery? Does it sound like something else? What's the most efficient way to diagnose and address the issue?

Any guidance and advice would be greatly appreciated.

Thank you in advance,

Chindsey

 

With a hybrid vehicle, the 12 volt battery's job is not to start the car. Instead, it starts the hybrid system, and, once the hybrid system is started, the hybrid system decides when the car can run on battery power and when it needs to be using the internal combustion engine, in which case, the hybrid battery is what actually starts the ICE.

That being the case, the 12 volt battery in a hybrid vehicle has only a fraction of the cold cranking amps that the 12 volt battery of a non-hybrid would have.

So, if you were playing around with the settings for any length of time while the car was in the accessory mode, you likely drained that less powerful 12 volt battery. It may be the case that the 6 year old battery was close to being ready to be replaced anyway. What you need to do is to have a load test done on the 12 volt battery by a dealer, other mechanic, or auto parts store to determine whether it has any life left in it, and that will determine whether you need to replace it or whether it can be recharged and still have some use left.