12v battery issue

[David71201]

info:
2015 Model S 70
175K miles
new 12v battery installed at service center 5 months ago

I was supercharging two days ago (in a rainstorm). At 47%, it suddenly stopped charging. An alert said low voltage. Soon after that an alert said unable to drive. I had a friend pick me up and take me home (I live nearby).

Yesterday, I went to the car and discovered that the 12v battery was so low, the handles did not extend. It barely had enough to open the trunk. So, I knew that if I could jumpstart it, maybe I would be able to drive it. I still think that something is wrong to cause the battery to drain, but driving it to the service center (128 miles away) beats the $600 cost to have it towed there.

Online videos showed me how to remove the nose cone and there should be two bolts there to attach the jumper cables. Unfortunately, when I removed my nose cone, there was just one bolt. So, I opened the frunk and removed the center cover and the fusebox cover to reveal two terminals to which I could jump.

The fusebox cover diagram indicated that the passenger side terminal was the positive (see picture). I had a fully charged portable jumpstarter. I attached the red clamp to what I believe is the positive terminal (left post in picture) and black clamp to what I believe is the negative terminal (right post in picture). But when I attached the cables, the light on the portable charger was blinking red, indicating a problem. I then pulled my friend's ICE car beside it, turned off that car, and used regular jumper cables. Within 3 seconds, the clamp on the negative (right post in picture) starts to smoke. I immediately remove the cables.

My two questions:
1) Have I identified the positive and negative terminals correctly?
2) If I have identified them correctly, what was the cause of the smoke?

Is there a better approach to my problem than what I am attempting? Any suggestions as to my next step are very welcomed. Thanks.

David

 

[SoCal Buzz]

Have you checked owner’s manual for specific jump start process for your year?

Sounds like your DC charger or main battery have an issue, and 12V is not getting charged. Hopefully nothing shorted when you tried to jump.

 

[ATPMSD]

First, if Tesla installed the replacement battery see if you can get them to address the problem for you. I would think there is some sort of battery warranty?

One of the failure modes of batteries is a short. If I were you I would remove the battery and take it to a battery shop for testing. It will be unlikely they will have a replacement, in which case open a service ticket with Tesla to buy a new battery. You’ll probably have to pick it up. If you will notice the part number of the battery you may be able to purchase a new battery online and have it shipped to you.

It could be something more serious, of course, but this will at least eliminate the battery as the source of the problem.

Good luck!

 

[David71201]

Have you checked owner’s manual for specific jump start process for your year?

Sounds like your DC charger or main battery have an issue, and 12V is not getting charged. Hopefully nothing shorted when you tried to jump.

That's what has me scared. I thought what I was doing was correct, but the result was definitely not good. Should I bite the bullet and spend the 600 to get it towed to the SC, or is there an option I should try first? Thanks for your help.

 

[David71201]

First, if Tesla installed the replacement battery see if you can get them to address the problem for you. I would think there is some sort of battery warranty?

One of the failure modes of batteries is a short. If I were you I would remove the battery and take it to a battery shop for testing. It will be unlikely they will have a replacement, in which case open a service ticket with Tesla to buy a new battery. You’ll probably have to pick it up. If you will notice the part number of the battery you may be able to purchase a new battery online and have it shipped to you.

It could be something more serious, of course, but this will at least eliminate the battery as the source of the problem.

Good luck!

Great idea. I'll see if I can remove the battery, but I know that isn't trivial. I'll also check with the SC to see if the new battery replacement comes with some sort of warranty. Thanks for the suggestion.

 

[vcor]

I'd recommend charging the battery (with an external battery charger) and seeing what happens (without driving). After it's charged, remove the charger. If the voltage is immediately low or it can't be charged, likely the battery failed. Since it is so new, that seems unlikely. If it charged ok, see if it retains the charge for a day or two in the car. I suspect the DC-DC inverter within the car may have failed, which no longer charges the 12v battery. If that's the case the cost and effort to repair is considerably larger. Without the DC-DC inverter charging the 12v battery, it will be drained within 48 hours (and as quickly as 8 hours).

The manual shows where to connect the 12v jump/charger in the nosecone. Normally there is a positive stud for connection, and you use the metal area nearby for the negative connection.

 

[SoCal Buzz]

That's what has me scared. I thought what I was doing was correct, but the result was definitely not good. Should I bite the bullet and spend the 600 to get it towed to the SC, or is there an option I should try first? Thanks for your help.

Check the manual on how to properly jump start and charge. Then per @vcor see how it does over a day or two. Also, you haven’t mentioned status and charge on your HV battery and whether it can charge, which you can test after 12V is working.

 

[KalJoMoS]

My two questions:
1) Have I identified the positive and negative terminals correctly?
2) If I have identified them correctly, what was the cause of the smoke?

Is there a better approach to my problem than what I am attempting? Any suggestions as to my next step are very welcomed. Thanks.

David

Why you did not followed that clear guide on the image that instructed you to connect neg.cable to chassis point? This point or pole that you used is NOT negative pole as you would see on 12V battery. Hope that this has not given you any additional issues.

 

[cbdream99]

Great idea. I'll see if I can remove the battery, but I know that isn't trivial. I'll also check with the SC to see if the new battery replacement comes with some sort of warranty. Thanks for the suggestion.

The replaced 12v battery itself has a 1 year warranty but it is likely something else causing the problem...

 

[nsartor]

I know this thread is old but what you did was short out the battery! BOTH of those points are positive connections. It was VERY stupid of Tesla to leave the passenger side one BLACK as it is the cable connected to the POSITIVE of the battery. The other side has a fuse in it. The OP was supposed to connect the negative on the jumper cables to a GROUND (any bolt) on the chassis. The negative battery terminal is just connected on the passenger inside of the wheelwell but you can't see it without pulling everything off. If the 12V battery is completely dead because of an internal short, you could disconnect the left (passenger) nut to the positive battery terminal and still jump it. Sometimes have to let the jumper cables sit for a few min to boot up the computer. You shouldn't need to have the ICE vehicle running - it only takes a little bit of juice.