Posts: 105
Joined: Wed May 22, 2019 6:16 am

12V battery issue... maybe overcharging issue?

In May 2020 I had the 12V battery replaced in my car under warranty.

Last friday I smell a sulfur smell coming in the climate intake vents. A quick internet search said this was almost certainly the 12v battery, but being an electric car and fires being scary I took it to the closest dealer and Ubered home.

They said the smell was, indeed, coming from the 12V battery ($343 diagnostic, woot) and that it would be $550 to replace it. They also said,
Recommend additional diagnosis of the electrical charging system after battery replacement.
Comments: There is a discharge battery warning coming on and additional diagnosis is recommended to verify new battery is not being over charged.
The battery discharge warning is almost certainly the roadtop carplay adapter. Since I installed it, it displays things on the screen long after the car is "off".

So, I ignored that part of the diag, bought a battery from the parts dept for $150, and replaced it myself in half an hour.

The battery I took out was HOT. As in, so hot that I couldn't touch it with my bare hands... and felt compelled to wear a face shield, in case it suddenly did something.

After replacing the battery, the sulfur smell is 100% gone. But, every time I start the car up for the first time, there is ~5 seconds of smelling every so slightly like burning plastic.

... think I should be concerned, and there is an overcharging issue going on? What might cause an overcharging of the 12v battery?

Posts: 75
Joined: Sat Sep 06, 2014 10:11 am
Location: Davis, CA USA

Re: 12V battery issue... maybe overcharging issue?

Did you measure the voltage of the battery when removed? Does it remain hot? Wondering if there is an internal short. If it's something in the car that is causing this you won't have better luck with a new battery. Can you have your charging system checked?
Neil L.
2014 i3 Rex, Giga World, all the trimmings.

Re: 12V battery issue... maybe overcharging issue?

Does the new battery get hot? If it does, indication something is wrong in the car's electrical system. If it doesn't, then more than likely the previous battery was just defective.
Posts: 105
Joined: Wed May 22, 2019 6:16 am

Re: 12V battery issue... maybe overcharging issue?

What would cause an overcharging issue?
Posts: 311
Joined: Fri Nov 25, 2016 11:23 pm
Location: USA West Coast

Re: 12V battery issue... maybe overcharging issue?

As a few other posters have asked, have you found that your new 12V battery is hot to the touch?

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