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12v battery questions

12v battery questions

Is there a warning signal when the 12v battery gets low or otherwise begins to malfunction? What is the normal lifetime for this battery in years or miles? The Owners Manual seems silent on these matters and all I've found online are stories of sudden death. I'd like to be proactive and replace the battery before getting stranded.

sheldon.mike1010 | October 28, 2019

Other owners here have reported that Tesla can detect battery deterioration and will contact you if they see it.
12V batts were occasionally an issue on early cars, but appear to be reliable on Model 3's.

jebinc | October 28, 2019

So, longevity the same as an ICE car 12v battery???

lbowroom | October 28, 2019

Yes, so anywhere from 1 day to 8 years.

jebinc | October 28, 2019

@lbowroom - After some time observing your posts, I have determined few of them are constructive.

sheldon.mike1010 | October 28, 2019

#jeb
Model 3 likely hasn't been in service long enough. Production started in 2017 and ramped up seriously in early 2018.
After a while we'll see if it's the usual 3/4 years lifespan.

Joshan | October 28, 2019

jebinc | October 28, 2019
So, longevity the same as an ICE car 12v battery???

Actually wondering if it would be worse. Based on the process of powering the car with the 12V and charging the 12V with the battery pack. It seems like it would be a lot more charging cycles than in a ICE car.

However, this is based on common sense thinking, not scientific evaluation.

jebinc | October 28, 2019

@sheldon.mike1010 - Thanks for the constructive post. So, I assume the 12v Tesla battery is nothing special. Does it have a "Group code"? Can you find replacements at Costco or an automotive store, or are these 12v batteries "Tesla proprietary"?

Joshan | October 28, 2019

@jebinc take a look at this, it will likely answer all your questions.

https://teslatap.com/articles/12-volt-battery-compendium/

lbowroom | October 28, 2019

jeb. my posts have an edge to them, but 3-4 years is about right for average life of batteries these days. Go out a few sigma and 1 day to 8 years isn't a terrible answer.

To answer the OP question in long form rational explanation would start with, "the 12V battery and how it's charged in a model 3 is similar to 12v batteries and charging in any vehicle. Therefore it should follow the same likelihood of failure as any other car make. There is no reason to plan to change the 12v battery out on a maintenance schedule......

gmr6415 | October 28, 2019

I don't know if this applies or not, but my Honda Civic Hybrid charged the 12 battery used for cabin functions similarly...through a BMS of some sort, not an alternator. I'm in FL where batteries don't last much more than 4 years at best. My 12v battery lasted 8 years in my HCH. When I sold the car at 15 years old I was still only on my 2nd 12v battery.

lbowroom | October 28, 2019

you cannot predict on a single vehicle when the battery will fail, etc etc etc.

I think my posts convey the same message in a way that's more satisfying to me

jebinc | October 28, 2019

@lbowroom - Fair enough. Perhaps those other BS threads were just getting to me more than usual this morning. I am quite surprised by M8B's posts (the former "keep it real" advocate). Not what I expected... Anyway, I will slap myself to getting back on topic as I don't want to pollute another thread with "troll" talk.

Does the M3 battery have a "Group Code"? Does anyone know?

Joshan | October 28, 2019

@lbowroom as I have said numerous times in the last week. Sarcasm on this forum does not seem to go over well.

lbowroom | October 28, 2019

Believe me jeb, I'm as raw as everyone about those threads. The culprits are clear to me. However, you've been what appears to be intentionally vague about who the think the problem people are.

sheldon.mike1010 | October 28, 2019

Lots of $$, but here is an aftermarket battery that is lithium, not AGM. https://evtuning.com/products/model-3-lithium-12v-battery-replacement

Tesla will replace what we have for free if it fails.

jebinc | October 28, 2019

@lbowroom - You are correct. I refuse to add fuel to the fire. This isn't elementary school. Back on topic, please.

sheldon.mike1010 | October 28, 2019

#Joshan
Great article there

jebinc | October 28, 2019

@sheldon.mike1010 - Thanks again for the constructive, "on topic" post! I will do some more research and will scour the TMC forum for more details, if they exist.

jebinc | October 28, 2019

@Joshan - Thanks, will check out the article you posted. Thanks for staying "on topic".

lbowroom | October 28, 2019

It's a conventional automotive 12v battery. As long as the Tesla emulation of charging is similar or better than that of conventional alternators in ICE cars, the results will be similar to results across the industry.

lbowroom | October 28, 2019

Sudden failures of the battery are reported because that's a disruptive event. No one reports when then battery functions correctly. There's is no way a users manual can address predicted failure rates of the 12V battery. Furthermore, there is no car maker in the world that publishes the expected failure rate of the components in their cars. If they expected a high failure rate of a component, they would work to fix that problem before it existed. When unexpected failures happen, they try to find root cause and fix that problem reactively.

wayne | October 28, 2019

Follow and read Josram’s link. Excellent info about the 12v battery.

AZTesla | October 28, 2019

@Joshan - Thank you for posting the reminder about that fine TeslaTap webpage on 12v batteries. I was discussing this issue with another M3 owner on Saturday and we were considering a proactive approach in replacing our 12v batteries this winter before the summer heat returns, perhaps with a resulting catastrophic failure. I suppose it is comforting that the electrical monitoring systems on the M3 will give us some degree of warning before that happens.

RoadDevil | October 28, 2019

I hope Tesla will soon replace lead acid battery with capacitor or lithium-ion battery. The traditional batteries just do not fit into EV technologies.

gballant4570 | October 28, 2019

Just re-read the "please read before posting...." thread, and did not find a requirement for post constructivity. That came as quite a relief.....

jebinc | October 28, 2019

-@gballant4570

You are correct. For those wondering, this is the actual language.

"Tesla’s forum provides an online meeting space for owners and enthusiasts to exchange ideas that are entertaining, helpful and useful. We encourage you to participate and only ask that you be respectful of others. Don’t post messages that are obscene, vulgar, hateful, sexual in nature, infringe on the proprietary rights of others, or impersonate or misrepresent yourself or other individuals, including Tesla employees. Only post material which you own or for which you have received a copyright license. Whatever you post, we reserve the right to copy and use. We also reserve the right to edit or delete your post as well as suspend your account."

Joshan | October 28, 2019

is it me, or did that post just disappear?

Joshan | October 28, 2019

er, it just came back. very odd! maybe my browser somehow.

kaffine | October 28, 2019

I got a little more than 12 months and 36k miles from mine. No warning, it failed during a software update. I had thought the software updated failed but found out it was a battery. Tesla SC and mobile tech were busy so they let me bring the 12V battery in and swap it out myself.

I couldn't find an aftermarket one in stock near me.

The number on the battery is 85B24LS it is a 12V 45Ah(20hr) and was a wet cell not AGM.

I hope to find an AGM next time I have to change it. I did see an aftermarket lithium battery available online. Not sure I really want to use lithium for it though.

jordanrichard | October 28, 2019

Ibowroom, no it is not a conventional 12 v car battery. The battery is physically smaller than a typical car battery and it is not designed to serious amperage like a typical battery because it doesn’t need it.

Anyone thinking they can go to their local Sears and have them throw a battery in for you, best of luck to you. Don’t say nobody warned you.

gballant4570 | October 28, 2019

There is a battery warehouse in town (Westminster, MD) that usually has anything you might be looking for. They usually cost more than other sources though. I guess if your car won't move without it you might not mind paying a bit more.
I would think an AGM might be preferable to lead/acid - is the OEM AGM. or lead/acid?

lbowroom | October 28, 2019

Jordan, my comments have to do with battery technology that would affect lifespan. The points you bring up our true, however they aren’t really relevant to the conversation.

lbowroom | October 28, 2019

In fact, less current demand will increase the life of the battery, not shorten it.

drrock75k | October 28, 2019

Thank you, Joshan, Lots of useful information in your teslatap link.

-TheJohn- | October 29, 2019

lbowroom is definitely not the Droid you're looking for btw although I get being annoyed with repetitive posters of all stripes. One can be pushed too far is all I'll say there.

Insofar as the actual topic.. I know jack about batteries and their lifespan. Thanks for the conversation.

kaffine | October 29, 2019

gballant4570

It is a wet cell lead acid battery.

TM3Q | October 29, 2019

Just in case your wondering why our ICE battery don't last long....

First many drive for short trips and don't allow the battery to recharge fully so the lead battery will degenerate with time because of chemical reaction that creates corrosion and sulfation.

Chemical reaction increase with heat so if your battery is low and it's hot well you will shorten the battery life quickly.

How to destroy a brand new lead battery in a few days....just let it sit completly discharge for hours....add some heat and bye bye battery.

I could add many more situation that will kill or shorten a lead battery......just to say it's not really the lead battery that don't last long, it's more the way we use them without proper maintenance....

Cheers

TM3Q | October 29, 2019

Oh and the difference between Tesla battery use and a ICE battery use......ICE use battery to start the engine (wich could easily deplete a battery if done for long use) and Tesla don't use the battery to start an engine :-)

If the Tesla battery is charge properly it should last longer than an ICE battery unless the ICE owner maintain is battery properly.

jordanrichard | October 29, 2019

Now this is pure anecdotal, but there does seem to be some correlation between low mileage (low usage) cars and short lived 12v batteries. When this was the "it" topic on the MS forum, almost every person that stated they had a problem, had relatively low miles on their car.

The same issues happen with ICE cars.

jrweiss98020 | October 29, 2019

Unless you manually connect a trickle charger, the 12V battery in an ICE car will slowly discharge. Leave it parked long enough, and it will fully discharge. Starting batteries in ICE care are generally NOT designed to withstand repeated deep discharges.

OTOH, the 12V battery in the Tesla is a deep-cycle AGM battery that is kept topped off by the car system, so it should show minimal cycle wear.

Frank99 | October 29, 2019

OK, let's talk.

An ICE battery has to deal with high-current starting discharges, and high temperatures (it's over 200F/93C under the hood when you park the car). As a result, an ICE uses a "starting" battery designed to optimize it's life in this kind of usage.

A Tesla Lead-Acid battery doesn't have to deal with the several hundred amp starting discharge, and is generally in a far more temperate climate - it can still get hot under the hood on a hot, sunny day, but it doesn't get that hot every single time you use it like it does in an ICE. As a result, Tesla uses a "Deep Discharge" battery, used in RVs as a house battery, golf carts, etc. Looks the same to you and me, generally available in some of the same sizes as a starting battery, but the lead plates inside have a slightly different chemistry, are spaced differently, along with several other internal construction differences.
So there.

Joho.keith | October 29, 2019

If you assume the 12v life span in a model 3 will be similar to what is observed in the model S (had one for 5 years) then count on about 4-5 years. As others have said, it could be shorter or longer. That is very comparable to the lifespan of a deep cycle battery on a boat.

Joho.keith | October 29, 2019

If you assume the 12v life span in a model 3 will be similar to what is observed in the model S (had one for 5 years) then count on about 4-5 years. As others have said, it could be shorter or longer. That is very comparable to the lifespan of a deep cycle battery on a boat.

TM3Q | October 29, 2019

Hum I change my lead battery from my old ICE cars every 7 to 8 years average....

I just hope I can do the same with my Tesla Model 3!

Frank99 | October 29, 2019

Lifetime of Lead-Acid batteries is wildly variable. Here in Phoenix, 3 years is a reasonable lifetime due to the heat in the summer. I've noticed that some cars eat them faster than that, and others might go 5 or 6 years. It's kind of a mystery as to how long any particular battery is going to last in any particular car.

TM3Q | October 29, 2019

I did an investigation about battery failures a few years ago and my result were;

On top of my list:

Battery failure due to bad operator maintenance!

Misuse of battery charger or charging with a cheap battery charger or charging the wrong type (Std,Gel,AGM)

It's super easy to degenerate a lead battery and you only need one time mistake to reduce battery life even with a brand new battery you can destroy it in pretty short time if not properly use!