When to Replace 12v?

[Mulkogi]

I had mine changed out a few weeks ago and my model three is a May build of 2021. Mobile service charged $130.00.

That’s actually pretty good price for a mobile service replacement. Might go that route with mine. Also a May 2021 build

 

[cbdream99]

Back in the day when I owned a 2018 Model 3, I pro-actively swapped out the 12. battery at 3 years old. I had two reasons:

1. To avoid unexpected 12v problems. If the early warning system is much improved that may not be a consideration today
2. My car usage events were often more than 24 hours apart and I was seeing high vampire drain. I reasoned that an old (but not dead) 12V may have been a contributor.

I have experienced #2 the same way.

 

[Johnny Vector]

If a person keeps a small 12vdc cell inside the front bumper jumper panel like the A123 cell or has a jump pack, is that enough power through that jump circuit port for the car to presumably open the contactor allowing the vehicle to then run off the PCS DC2DC even if the LV FLA cell has dropped below a low voltage threshold or even "completely failed" ?

Or is that jumper circuit isolated to the doors/entry systems exclusively? And a jump pack would be required to be applied directly to the LV battery terminals to activate the PCS?

I believe the wires in that panel are diode-connected to just the frunk. Apply power, frunk opens. In any case, I've tucked a small A23 12V alkaline in a holder in there and I keep a lithium jump-start pack in the frunk. Never had to use it, and I don't even know if the A23 battery has enough current capability to open the frunk, but it's there anyway.

 

[cbdream99]

I believe the wires in that panel are diode-connected to just the frunk. Apply power, frunk opens. In any case, I've tucked a small A23 12V alkaline in a holder in there and I keep a lithium jump-start pack in the frunk. Never had to use it, and I don't even know if the A23 battery has enough current capability to open the frunk, but it's there anyway.

Do you regularly check the A23 battery and the lithium pack to make sure they are working and charger? Can the new lithium ion low voltage battery be jumped?

 

[Johnny Vector]

Do you regularly check the A23 battery and the lithium pack to make sure they are working and charger? Can the new lithium ion low voltage battery be jumped?

I do check the charger pack. I don't bother with the A23; it's alkaline so I expect it to last 10 years. The pack also claims 98% SoC after sitting for a year, although I have my doubts about the accuracy with essentially no drain, so I charge it once a year.

 

[Silicon Desert]

My personal opinion? I always pro-actively replace 12V batteries around 3 years, to avoid the inconvenience of a random 12V battery failure. The MY and M3 batteries are inexpensive and simple to replace.

Yes that is also me. I replace the battery before the 4-year mark especially since I often take long trips. Just like batteries in my older ICE cars.

 

[leoita]

It's strange how Tesla 12V battery dies after 2-3 years while my Prius 12V still runs strong after 9+ years..

 

[Mulkogi]

It's strange how Tesla 12V battery dies after 2-3 years while my Prius 12V still runs strong after 9+ years..

Yeah but you don’t get rainbow road on the screen

 

[leoita]

Yeah but you don’t get rainbow road on the screen

True, but I wonder why tesla 12V dies so quick. Is it due for not being constantly charged enough? The inverter on the Prius takes care of the 12V and the HV battery.

 

[Johnny Vector]

True, but I wonder why tesla 12V dies so quick. Is it due for not being constantly charged enough? The inverter on the Prius takes care of the 12V and the HV battery.

If you read the thread, you'll see that the answer is "it doesn't". There were significant numbers of problems in the past, but recently it seems much more rare.

You're comparing your experience (a single data point) with everyone who has posted about having a problem with their Tesla. There are literally millions of Tesla owners who have never had a problem with the 12V battery. If you really want to compare you need to compare the odds ratio of similar populations.

 

[everydaychris]

That's the important fact that people keep missing: Teslas have a feature built-in the monitors the health of your 12v battery. It can predict (with an alarmingly high amount of accuracy) when it will fail and warns you via a message on your dash weeks/months in advance.

Even in rare ICE cars that offer something similar, the demand of a battery to turn over an engine is dramatically higher impact especially in cold temperatures. Due to this, it's far more difficult to predict when a 12v battery in an ICE car will stop being able to start the engine. 12v batteries in a Tesla are for accessories (wipers, headlights, radio, at al) and the draw from these is very low comparatively speaking and consistent. Much easier to track anomalies and predict when that voltage will drop to a dangerous level.

Now, are there times where a 12v battery just fails for now reason and ahead of it's typical life expectancy? Of course. This is a known failure type in the 12v realm and it's the same for a Tesla as it is an ICE car because it's due to manufacturing differences. 12v battery duty in a passenger vehicle is a complex and complicated thing but it's far less complex, far less complicate and far more reliable in a Tesla than it is an ICE car due to what their job description is between those two technologies.

This should be a another non-issue but threads like this scare people away who haven't experienced them first-hand. Don't sweat it. Just drive the thing and it will let you know if/when you need to replace the 12v battery 99% of the time. People are so used to having to maintain an ICE car they almost search for items they can be proactive about and the reality is it's a waste. It feels weird at first, but just embrace it. The days of having to micromanage a machine to keep it on the road when you need it are over. All hail the EV!

that's awesome! Thanks for the info man!

 

[Watts_Up]

... for those with the dinosaur 12v batteries,
is there a certain voltage, time, miles you guys replace yours?

I went to the secret service menu and no issues.
When the car is on the 12v is running around 13v?
Currently at 3 Years 57k miles

You should get a Bluetooth 12V Monitor to check your 12V battery status
(and make a video of its usage on your YouTube channel).

Note: You will need to download the BM2 phone App to access the Bluetooth information.

Android BM2 - Apps on Google Play
Apple : ‎Battery Monitor BM2



When using the Service Menu the car is 'running' and not 'sleeping',
so the 13V is the Voltage of the output of the DC/DC inverter.

The following graph shows from left to right, the car "sleeping",
then from 6 am to 11:30 am, the car was "running", and thereafter was parked and sleeping.

The DC/DC inverter is running when driving, to avoid to drain the 12V battery when using accessories like high beams, HVAC,...
This is very similar to the usage of an alternator on an ICE vehicle.

If the 12V battery is healthy, when the car is parked fro few days, the DC/DC inverter is activated when the battery gets below about 12.5 V.
Typically the DC/DC inverter get activated every two or three days and run for two hours at about 14.5V. See below diagram:
When parked, the propulsion battery usage is about 1% a week while keeping some devices connected and running time to time the DC/DC inverter.

You can detect if a 12 V battery is unable to keep its charge and needs to be recharged several times a day. See the following graph:
This indicates that the 12V battery needs to be replaced:

Note: I still have the original 12V battery after 5 years on my Model 3.

Note: I wish that Tesla provides such graph display to check the status of the 12V battery instead of a warning not providing too much notice.
Even in the case of the new 16V Lithium-ion batteries, such information would be worthwhile considering the small Amp capacity of those ion batteries.

 

[TesLEEZ]

It's strange how Tesla 12V battery dies after 2-3 years while my Prius 12V still runs strong after 9+ years..

While true, the 12v battery in a Prius will last 9 years. That doesn't mean you shouldn't replace it sooner. My 3rd gen prius fuel mileage decreased at about 5 years. It turned out the 12v battery was the culprit as the gasoline engine would have to turn on and run more often. The prius does not have a starter for the engine, instead the computer instructs the electric motor to use power from the traction battery to start the engine. So the 12v system can operate just fine even with a very weak battery with low capacity. It just means when the voltage drops low more often, then the engine will need to kick on and run more often, lowering your fuel economy. This is well known with Prius's. Basically with the car turn off and the battery resting for a few hours, check it with a voltmeter. If it's at about 12v, then it needs to be replaced for optimal fuel economy. Needs to be at about 12.3v minimum after being fully charged and resting for a few hours. 5 year is the average for these batteries when looking at fuel economy. But the car will still operate fine for many more years with the battery at low capacity.

 

[Jeffrey@1344]

I have a 2019 Model 3 with 11,000 miles on it. Last year, with no warning of any kind, the 12 volt battery died and locked me out. No big deal? How about the fact that it happened while the car was in a very busy car wash and no one could get into it. They had to tow it out with lots of angry people looking at me. I never even knew there was this other battery.
Everyone is posting about warnings, replacement proactively.
Now I am concerned if I’ll get a warning if it happens again.

 

[cbdream99]

I have a 2019 Model 3 with 11,000 miles on it. Last year, with no warning of any kind, the 12 volt battery died and locked me out. No big deal? How about the fact that it happened while the car was in a very busy car wash and no one could get into it. They had to tow it out with lots of angry people looking at me. I never even knew there was this other battery.
Everyone is posting about warnings, replacement proactively.
Now I am concerned if I’ll get a warning if it happens again.

I hope it won't die in a drive thru during lunch, it happened to me in the 90s! It's not funny and embarrassing, but at least an ICE car, there will be samaritans able to help you push it away. For Tesla, everyone will take out their phones and snap a picture and post it online.

 

[Midnightsun]

3-4 years is normal (regardless of mileage). Ask service to check the 12V battery before your warranty expires and they might replace it proactively. I did that on my previous Model S, after the 12V died in my wife’s 3-year-old Model 3.

Our Y is 3 1/2 Years old, have a mobile appointment coming up next week to have the hepa upgrade installed. Today I asked via the app how much it would cost to replace the 12v battery as preventative maintenance while they were doing the hepa thing. Came back with 0$ and a note that says 12v battery requires replacement. I can only assume they are doing this under warranty.

 

[Z_Lynx]

Next March my Y will be 3 1/2. Low miles. Would love it if they would preemptively replace the 12V battery before it exceeds the 4 yr warranty at no cost.

No indication there is any current issue with the battery, however.

 

[Krash]

Six and a half years and 140,000 miles on my original S75D 12v. I thought about preventative maintenance, but at this point, I’m kind of curious how long it will go.

 

[Midnightsun]

Six and a half years and 140,000 miles on my original S75D 12v. I thought about preventative maintenance, but at this point, I’m kind of curious how long it will go.

I highly suggest you swap it out as it may fail at the worst of times which is usually the case. You are definitely on borrowed time.

 

[Pianewman]

Six and a half years and 140,000 miles on my original S75D 12v. I thought about preventative maintenance, but at this point, I’m kind of curious how long it will go.

If I lived alone, in a temperate climate, and had no work responsibilities, I would do the same thing.

Considering it's a very cheap replacement, I'll keep proactively replacing mine, rather than worrying and complaining about getting Tesla to replace is for free.