12v battery for high mileage owners

12v battery for high mileage owners


I am wondering how the high mileage owners deal with the 12v battery. My X just died after 2.5 years and 41,000 miles. Couldn't open doors etc. Bad hydrogen sulfide smell, so possibly leaking and not due to just a "dead" battery. There was no warning. I had just gone out and picked my daughter up 90 minutes before I went to check on my X. Tesla service called a tow truck, he was able to get it charged up over several minutes so he could open doors and back up to load on truck. My issue is, when the warranty expires, I don't want to have to pay for a tow truck to take it 45 miles just to change a 12 v battery. What options do I have? As most of us have done, in our old ICE cars, take the battery out, use another car, go to auto whatever store and exchange for a new battery. Drive back home and pop it in. Do I have them preventively change it every 35-40k miles at a service visit, do I learn how to change it, ????


jjgunn | August 13, 2018

I've been told the 12v battery is under the frunk.

I have 1,500 miles on my X. I'm already looking at a $450 Lithium Ion 12v battery - long before any of this crap happens to me.

burdogg | August 14, 2018

jjgunn - look into your options and discuss with understanding from others that I have gleaned is that you don't want a lithium ion 12v battery for the Tesla. I don't remember why and all the specifics but make sure you do your research ;)

bob | August 15, 2018

I get why Tesla has kept a lot of this 'routine' maintenance issues secretive over the past few years. IMO it's been to protect the brand name and retain a high level of user satisfaction (reputation). As a infant car manufacturer they can't afford to have a bunch of unsatisfied users. Also IMO this HAS to change as the road is gonna be full of M3s in the not too distant future. Your local Pep-Boys employee behind the counter is gonna need to know how to do the simple stuff like swapping out the 12v.

I think it will be interesting to watch if Tesla (or the industry as a whole) does some sort of out-reach to vocational schools on basic EV maintenance issues. I'm a tinkering kind of person. I need to know how stuff works. I may not be able to fix it, but not understanding what I'm driving is not in my nature. I know I'm not alone in this personality makeup. I think I may be in the minority for the group of people who have been the initial adopters of Tesla. But I don't think that is the case as the masses start to become EV owners.

To the OP: The vehicles do have a diagnostic routine to check the health of the 12v system. I've got an MS with 40k + miles and have seen it. It provided lots (like a month) of warning that the 12v system was in need of replacement. I'm wondering if the failure you experience may have been an anomaly? Was it some sort of spontaneous failure brought on by overheating or some other environmental issue???

@jjgunn - yes the 12v battery is in the frunk just to the passenger side of center, under the cover where the emergency high voltage disconnect is. | August 15, 2018

To add to bob's details, you can replace the battery yourself - it's no harder than any ICE car, but it is smaller and requires the same type (AGM). I gather in 99.9% of the time, your Tesla will warn you weeks before it fails. Your failure, without warning is very rare - perhaps due to a cracked battery case (which can happen to an ICE car too). Sound like a manufacturing defect in the battery.

Do not waste your money on a lithium-ion 12v battery. It will last about half as long as the AGM battery. It is very poorly suited to an EV, where the battery charges and discharges frequently. It's quite different application than an ICE car. In addition, it is unclear if the unheated lithium-ion battery will work properly in low temperatures. The main pack self-heats if necessary, so it's not an issue for that battery.

jerryk | August 16, 2018

In general that is how 12V AGM batteries die. Very little warning. A dead short cause by plate failure. AGM batteries are great while they work (no maintenance, little fluid to spill, etc). But they fail with few symptoms. And they can be costly. I paid close to $500 each time one failed on my BMWs. $200 for battery, $300 for install and calibration of the BMS.

Sleepydoc1 | August 16, 2018

Thanks everyone. No warning. Had a weird episode a week before where the doors would barely open and the car asked to recalibrate the doors. No dash lights or anything went off with battery warning. Wasn't sure of what to make of the door thing. Now I will suspect the battery if I see it again.

The tow truck guy did take that panel off and connected to charge the battery. I can look into that more. I can ask the Tesla service people what it takes to change the battery myself. I just had no idea where it was at that time. Much cheaper (as jerry suggests) to do it myself than pay for a tow, a battery and service. AAA could cover the tow though. Much less time to do it myself as well.

Luisparada | August 16, 2018

Wouldn’t the 12V battery still be covered under the basic 4-year new vehicle warranty?

davidahn | August 16, 2018

AAA roadside service plan. I've been a platinum member for over 10 years, rarely have to use it. I don't think I'll ever get my money's worth, but the peace of mind is VERY nice.

Sleepydoc1 | August 17, 2018

It was completely covered, but I'm 2.5 years into that 4 years. Would AAA replace this battery?

Agree David - AAA has brought lots of peace of mind.

jerryk | August 17, 2018

My first call would be to Tesla Service's 800 number. I am a AAA member and that is what I would do.

The reason is Tesla service can walk you through getting into the car and resetting it in a number of situations. Or they can remotely diagnosis the car. Should this result in the need to dispatch a service, Tesla service can send a ranger with a new battery or a local tow service to jump or if needed, tow the car. They will also cover the cost of an Uber or Lyft to get you to your destination and go over the procedure for leaving the key inside the car (assuming they can get it open for you) so you do not have to wait for the tow truck.

Of course, the cost of this is covered by Tesla as part of your warranty.

Sleepydoc1 | August 17, 2018

Thanks Jerry.

Parteaga_2000 | September 4, 2019

I keep a small lithium battery booster in my frunk. This will allow me to charge the 12 V battery if it fails again.
You can find this at any auto parts store.
My battery failed and I could only open the frunk, nothing else. Fortunately the battery charged itself while waiting for the tow truck send by Tesla, then I did a reset and was able to continue home. Tesla replaced the battery.