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Serious 12v battery corrosion. 4,700 miles

holeydonut

Active Member
Supporting Member
Jun 27, 2020
3,668
3,185
East Bay NorCal
Just a reminder to ya'll that it's worthwhile to pop the frunk and remove that plastic trim that goes over the 12 volt battery every once in a while. There's a thread about this in the Model Y forums, but not in the Model 3 forum (at least, not that I found).


I bought my wife that fancy garage door opener do-dad. Installing it requires a Tesla mobile Tech and removal of the plastic shrouds in the frunk area. He found this... which the tech said was excessive for a car that has low miles and is driven around in a dry Northern California climate. (Car is 8 months old and has about 4,700 miles). That's the OEM battery from the factory.

Tesla Mobile techs aren't allowed to do a repair that wasn't on the original work order (and he had no spare 12v battery or replacement ground). So he just left it this way and Tesla Service will need to send someone back next week with a new battery. My guess is they'll replace and clean this up.

1654835386680.png
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
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Nov 28, 2018
17,570
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Riverside Co. CA
Yeah that looks really excessive. I had mobile service replace mine (12V) proactively (at my cost) since so many were dealing with 12v failures, and it was so relatively cheap compared to what my former BMW batteries used to cost.

When they replaced it in my driveway, I took a look when they took off the shroud and it didnt look anything like that, and my car was over 3 years old and like 28k miles at the time.
 

holeydonut

Active Member
Supporting Member
Jun 27, 2020
3,668
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East Bay NorCal
Yeah, that's why I posted this thread. @Fobia (Model Y forum poster) and I only saw this because we happened to be doing service on our cars that required removing the plastic shroud over the 12v battery. Luckily the issue was discovered before it caused a possible situation of being stranded down the road.

I think owners should make a habit of popping up that plastic cover in the frunk area to make some regular inspections since this is easy to miss.
 
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holeydonut

Active Member
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Jun 27, 2020
3,668
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East Bay NorCal
Ugh, Tesla service needs to improve.

Yes, they replaced the battery. No, the tech refused to clean up the negative ground-strap/cable. The guy just said "pour some Pepsi on it" and left.

Yeah, I used to rub cola on my crap batteries and scrub with a wire brush when I was 20 years old and driving a beat up Civic. This car costs $65,000 dollars and I don't have time to deal with this crap because I spend my free time posting on TMC.
 

holeydonut

Active Member
Supporting Member
Jun 27, 2020
3,668
3,185
East Bay NorCal
I bet the vent hose is kinked or plugged so internal pressure is building up. Maybe the cap was not removed and hose even hooked up at the factory. Check the hose!

Tesla tech said there was no vent hose on the Model 3 12v battery and just did a simple swap. Here's how the car looks after he just left.

1655147889797.png
 
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Tesla tech said there was no vent hose on the Model 3 12v battery and just did a simple swap. Here's how the car looks after he just left.
I'd be pretty disappointed in that service job. Hard to believe they didn't bother to attempt to clean the terminals off. I guess you have no other choice than to get diy and clean it up as best you can (and at least you got a new battery at all?). I believe there are some decent off the shelf purpose designed products to clean the terminals, but frankly you might be just as well off as the way you cleaned your old civic. Guess the price we pay for these things doesn't really lend itself to the highest servicing experience :rolleyes:
 
Tesla tech said there was no vent hose on the Model 3 12v battery and just did a simple swap. Here's how the car looks after he just left.

View attachment 816182
CRC battery cleaner and then follow up with CRC battery terminal protector. Cost like $10. Will take you 5 minutes max then se if it comes back over the coming weeks/months
 

iwannam3

Active Member
Aug 8, 2016
1,055
1,437
Washington
Tesla tech said there was no vent hose on the Model 3 12v battery and just did a simple swap. Here's how the car looks after he just left.

View attachment 816182
See that thing sticking out to the right of "Part description 12 V battery" on the edge of the battery? THAT IS THE VENT! It pulls off the battery and there is a plug in the new battery that is removed and the vent is inserted. Failure of the seal at the negative post and/or plugged vent line pushed acid up to the terminal post. That battery in the photo is 10 months old! Bring the car back and demand to see the service manager. Did you see it before you left or did they put the cover back on?
 
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holeydonut

Active Member
Supporting Member
Jun 27, 2020
3,668
3,185
East Bay NorCal
See that thing sticking out to the right of "Part description 12 V battery" on the edge of the battery? THAT IS THE VENT! It pulls off the battery and there is a plug in the new battery that is removed and the vent is inserted. Failure of the seal at the negative post and/or plugged vent line pushed acid up to the terminal post. That battery in the photo is 10 months old! Bring the car back and demand to see the service manager. Did you see it before you left or did they put the cover back on?


Don't get me started about that 90 degree connector coming out of the right side battery. I'm repeating the tech's words here... not my own actual thinking. I know that's a vent, but like I said, I spend all my time posting on TMC during Zoom meetings instead of being able to hover over a Tesla tech while they changed a battery. I can only argue with someone so much when they're literally paid to fix Teslas and I'm a loser.

The guy swore up and down there was no such thing as a clogged 12 battery vent, since Tesla's 12v batteries are maintenance free. He said the kits of whatever in their Model S don't have any cleaning equipment for battery corrosion (that's when he told me to pour some Pepsi). I asked him to at least get some dielectric grease on the new battery but he said Tesla never puts that grease on new 12v batteries. The tech punched out since he couldn't do anything further on the repair.

While I respect Jeremy's comments that yes, I can DIY this pretty easy myself... the whole point is how annoying it is to actually have to DIY. Edit: and please go check your own 12v batteries.
 
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