Near annual replacement of 12V battery is typical according to Tesla Service Tech

[Only Trons]

From personal experience: 12V replacement in early Model S is a significant amount of work. Lots of stuff to remove before attempting to shoehorn the old battery out and the new battery in ...

Been there, done that ....

Not disagreeing with those who have newer versions of the Model S ....

 

[Jughead135]

BTW, it's a simple matter to keep the 12v outlet in the console live all the time if desired. It's just a simple relay in fuse box #2 (the one on the passenger side under the removable cowling cover - see owners manual). Simply make up a jumper consisting of short piece of 14AWG or better wire with a couple of male 1/4" spade terminals. Pull the front most passenger side relay out and insert the jumper into the now exposed 1/4" female receptacles, and you're done, the 12v outlet is now on all the time. You can quickly change it back anytime by removing the jumper and reinstalling the relay.

Old thread, but I think this is the one I want! Lots of quotes in various places on TMC, but I think I've tracked this down to the original--apologies if I'm misquoting or failing to attribute properly. @Ingineer , fantastic stuff!

I'm looking for a way to get unswitched power. Some other places I've seen this have implied that at some point the MS changed, and this method no longer works. Can anyone confirm or deny that?

Ideally, what I'd really like is to have the USB ports be unswitched (for power)--frankly, the unswitched power I want is to my 12V outlet is just to feed a USB converter gizmo anyway, but I'd rather have it in a single wire. Any ideas on how to power these all the time?

Brand new car, so I'm not thrilled with the idea of tapping into 12V sources and/or drilling holes to run wires. Even the OBDII connection options I've seen are less than ideal, having to run a wire from that side to wherever. If I can just keep the existing ports juiced all the time, I'll be golden....

Thanks for any help/advice!

 

[Jughead135]

BTW, it's a simple matter to keep the 12v outlet in the console live all the time if desired. It's just a simple relay in fuse box #2 (the one on the passenger side under the removable cowling cover - see owners manual). Simply make up a jumper consisting of short piece of 14AWG or better wire with a couple of male 1/4" spade terminals. Pull the front most passenger side relay out and insert the jumper into the now exposed 1/4" female receptacles, and you're done, the 12v outlet is now on all the time. You can quickly change it back anytime by removing the jumper and reinstalling the relay.

I'm looking for a way to get unswitched power. Some other places I've seen this have implied that at some point the MS changed, and this method no longer works. Can anyone confirm or deny that?

Ideally, what I'd really like is to have the USB ports be unswitched (for power)--frankly, the unswitched power I want is to my 12V outlet is just to feed a USB converter gizmo anyway, but I'd rather have it in a single wire. Any ideas on how to power these all the time?

BUMP

Anyone with any ideas for converting existing ports to unswitched power...?

• Is @Ingineer's method still valid on newer (2020) MS?
• Any way to extend this method to include the USB ports?

 

[mrElbe]

The USB ports are powered via the MCU ( main screen ). You wouldn't want that to be powered all the time. Just insert a USB charging adapter into the 12V socket and use the method above to keep it on all the time.

 

[Jughead135]

The USB ports are powered via the MCU ( main screen ). You wouldn't want that to be powered all the time. Just insert a USB charging adapter into the 12V socket and use the method above to keep it on all the time.

That's what I figured re the USB (but, also figured I'd ask).

The problem with "the method above" is that it does not apply to newer cars. I gather in ca. 2016 the 12V system changed, at least insofar as the fuse panel is concerned. There is no such relay (at least, that I can identify) in the fuse panel of my 2020 MSLR+.

I'd love to be wrong--can you (or anyone) point me to where I can find the relay in my car...?

 

[Fiver]

Bump, as I'm looking for a way to keep the 12v system hot all the time on a late 2018 Model X.

 

[gaswhat]

Need to replace the 12v in my 2014 model S. I am going to do it myself since it is out of warranty (yes I watched videos).

I see 2 different references in this thread and on 12 Volt Battery Compendium – TeslaTap
C&D DCS33-UNCR
C&D DCS-33IT

I also see a post in this thread saying upgrading to the "new version" would require a software update: #446
Can I order either one? Or do I have to worry about doing a config change? I am guessing the config change is not something I can do myself?

 

[zwede]

If you need to change the config depends on what is in there now and what you can get for a replacement. Most likely your car is currently set to "C&D" as that's what the MS used for many years. Really early on they had (I think) Exide batteries but those went away in 2014 or so. However, I've heard Tesla has changed batteries again, this time to Atlas and these require yet another change of config.

 

[JRP3]

That seems strange considering I can charge any AGM lead acid battery with the same chargers. I wonder what is so different about them.

 

[airborne spoon]

That seems strange considering I can charge any AGM lead acid battery with the same chargers. I wonder what is so different about them.

They are all lead acid batteries just deep cycle ones, but yeah there is no logical reason to have to update software to change the battery. That's like saying your TV remote needs a firmware change when you swap from energizer to duracell.

 

[zwede]

Both the C&D as well as the Atlas are AGM. I don't think the original Excide was so that would explain the config change once you replaced Exide with C&D. Why a config change is needed for the Atlas I don't know.

 

[tga]

It doesn't make sense to me, either. I've switched multiple vehicles (cars, boats, jetskis) from flooded lead-acid to AGM, and never had a problem. No need to change charging parameters. It all just works.

 

[JPP]

Both the C&D as well as the Atlas are AGM. I don't think the original Excide was so that would explain the config change once you replaced Exide with C&D. Why a config change is needed for the Atlas I don't know.

Just a data point. My wife's 2015 S70D needed a 'routine' 12V battery replacement at almost 5 years. Ranger did the replacement a few months ago, and did update some kind of firmware. Not sure what the secret sauce is, but he stated that there were certain parameters for the replacement battery that differed from the battery installed in 2015. YMMV.

 

[ohmman]

My experience with 12VDC charge controllers is that there's a difference between AGM and flooded lead-acid parameters. One thing that comes to mind is that flooded batteries often have an equalize over-voltage charge applied to reduce sulfation, and that's really harmful to an AGM. I believe there are other differences, too, with discharge levels (flooded no less than 50%, AGM can go lower), etc.

A difference in brands of AGM? I haven't heard of that making a difference, but there could be something I'm missing.

 

[jerry33]

My experience with 12VDC charge controllers is that there's a difference between AGM and flooded lead-acid parameters. One thing that comes to mind is that flooded batteries often have an equalize over-voltage charge applied to reduce sulfation, and that's really harmful to an AGM. I believe there are other differences, too, with discharge levels (flooded no less than 50%, AGM can go lower), etc.

A difference in brands of AGM? I haven't heard of that making a difference, but there could be something I'm missing.

My experience with AGM hasn't been good, although I've never used them in a vehicle. Generally they have a pretty short life because they are sensitive to being fully charged.

 

[MDR SEA]

I got the 12v battery warning at ~70K miles. Drove on for another 3K miles then decided to change battery.
Here's the battery I used - https://smile.amazon.com/gp/product/B015DJ4QX4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Terminals are on the "wrong" side but the cables can span the void. I had to drill out the stub terminal adapters and shimmed between them and the battery lugs. Overall pretty easy adaptation.
Good luck.

 

[henderrj]

I realize the lithium-ion replacement batteries cost five times as much, but really, the fact that you won't have to see the battery for10 years has to be pretty appealing! we have the prototype one in mine, as I've often mentioned, and no I have no association with the company but, I really think it's well worth having the ohmmu.com battery. I have the prototype batmobile in mine, the original name Sean used, And I now have over 220,000 miles on my car. I think he put it in when it had 20,000. These are nice, inexpensive, cars. Why not spend the money?

 

[JPP]

Data point--

A week ago I had a Ranger out for a 2 year check on my 2018 P3D+ with about 12889 miles. The car was fine--no issues. Ranger checked the fluids (brake fluid and coolant), torqued the lug nuts, topped off the windshield washer fluid, changed my wiper blades. All good. $85. No complaints over 2 years.

The next day I get a firmware update to 2020.36. Installs fine. I do the usual reboot. All good.

I did not drive the car after the firmware update.

Fast forward to just a couple of days ago. I go into my garage to head out--and there is the characteristic rotten egg sulfur smell. I walk up to the driver's door and I can open the cat. But car just won't boot. I try the '2 thumb salute'--won't boot. I call Tesla Roadside to report the issue--they (like me) assume the 12V is bad. They call for a flatbed. While I wait (about 45 minutes) I open the access port on the front bumper and using a 12V supply I pop the frunk. I pull the access cover over the battery and meter the 12V battery--6V.

The car is tower to Tesla Dublin, where they replace the 12V battery under warranty. No reported issues with charging or DC-to-DC.

Kind of odd so close to a firmware update, and I assumed that the battery died from overcharging. Guess time will tell...

 

[Snowstorm]

Why do we still need a 12V battery? How come it can’t step down from the HV battery?

 

[Rocky_H]

but really, the fact that you won't have to see the battery for10 years has to be pretty appealing!

Whether that is a possibility depends on where you live, if it has moderate temperatures year round. Recharging a non temperature controlled lithium ion battery while it is below freezing destroys it.

Why do we still need a 12V battery? How come it can’t step down from the HV battery?

For safety, not wanting to keep a 400V system energized in the car all the time. They want to have that isolated and disconnected most of the time when the car is off.