This 11.9 V reading with engine off after 2 days resting. Any idea when should I consider battery change? The car has 17K miles and still under warranty till next year. First with this reading, is the battery bad or this is normal after 2 days overnight rest? I read in several threads that anything below 12 V after overnight rest is bad and means the battery is to be replaced. If this true, does the dealer change the battery under warranty for free if needed? Or I will pay for it!

 

Check the date code on the battery to determine install date. If it's old and the car has been sitting for a long time it may need to be replaced. You'll find that all of the electronics on this car will draw current when at rest, so it's a good idea to keep a battery tender hooked up when not in use. I've gotten into the habit of keeping mine plugged in all the time when it's not being driven. Lots of posts on this topic - search is your friend.

As far as dealer covering your battery under warranty, it may be considered a wear item and not covered. Best of luck!

 

Thanks Skiracer. I checked the date it is the original battery from early 2018. Meanwhile, I turned the engine on and the B Volt went up to 14.3 V. I think it could be normal to have 12 with the engine off. I will watch out for it hough. Thx

 

I suspect your battery is fine, and as long as it turns over w/ sufficient power you should be in great shape. I have also replaced my battery charging cables w/ one of those Li-ion charger packs so I'm never dependent on another vehicle to jump start. Also, my car is a 2010 so it's getting old!