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"Proactive" 12v battery replacement - good idea or overkill?

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The car needs to be plugged in all the time it is parked to extend the 12V battery life. Or to say it backwards, I think the battery will wear out quicker if the car is parked by not plugged in.

Simple thermodynamics, if the parked car is plugged in the battery will have many small self charges. But if it is unplugged, then it will drain to a lower charge and when plugged in it will need more current. Bigger charge oscillations would likely charging capacity loss. Then over time the battery fails.

Only coincidental observations when people complain their battery dies. But I keep the cars plugged in as much as possible and this Spring I plan to replace the battery…

Are you sure that the wall charger actually charges the 12v in addition to the car's main battery? (not trying to be persnickety as I have no idea.)
 
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Are you sure that the wall charger actually charges the 12v in addition to the car's main battery? (not trying to be persnickety as I have no idea.)
The high voltage battery (as in the 300-400V traction battery that powers the motor) has a DC-to-DC converter that charges the 12V battery as necessary (and the car can wake up to do so). The DC-to-DC converter works kind of like an alternator in a conventional car. The wall charger doesn't really have to do with it.

When you have the car parked and even with Sentry off, it drains the traction battery about 1 mile per day, which is pretty much from the car waking up and recharging the 12V battery to replenish the drain from the subsystems. If the car relied solely on the wall charger to recharge the 12V, people who park for a long time would come back to a dead 12V battery all the time (which doesn't happen, rather they just have less charge left in the traction pack).
 
The only "major" service issue I have ever had with my 2018 P3D is that I had to have the 12v battery replaced after about 2 1/2 years. Even though it was covered under warranty, I consider it a major issue because it rendered the car undriveable and it had to be towed. At that time, there was no warning that the battery was weak. One day, the car just would not power on and I had to have it towed to the nearest SC.

My question is, is it a good idea to have the 12v battery replaced periodically even if there is no sign of a problem? If so, when would you have it replaced? Every 2 years? Every 18 months?

Just curious what other Tesla Model 3 drivers are doing in regards to 12v battery replacement. Thank you!

Joebruin77
I replaced mine after two years given all the reports of battery failures. I have a 2018 M3P with 67,000 miles (it had 50,000 miles at replacement), and although the battery seemed fine, I didn't want to get stuck somewhere with a dead battery. I went with the Ohmmu lithium battery and in spite of all the reports of it causing the car to start throwing error messages, I haven't had any issues at all with mine. It's been absolutely trouble free. I have other uses for the OEM battery, and to date it seems fine (I keep it on a battery tender). I just know from experience that battery failures tend to happen at the worst possible time, and wanted to avoid that. So yes, I took the "proactive" route. No regrets.
 
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What's the best way to purchase a battery from a service center? I was thinking of putting in a service call and stopping by to pick it up. $85.00 is much cheaper than any parts place.
Your can email them and stop by to pick it up when it's ready. Or you might get the option of picking it up from a mobile technician. Find your nearest service center here and click on it for their email address Tesla Service Centers in United States | Tesla
 
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I replaced mine after two years given all the reports of battery failures. I have a 2018 M3P with 67,000 miles (it had 50,000 miles at replacement), and although the battery seemed fine, I didn't want to get stuck somewhere with a dead battery. I went with the Ohmmu lithium battery and in spite of all the reports of it causing the car to start throwing error messages, I haven't had any issues at all with mine. It's been absolutely trouble free. I have other uses for the OEM battery, and to date it seems fine (I keep it on a battery tender). I just know from experience that battery failures tend to happen at the worst possible time, and wanted to avoid that. So yes, I took the "proactive" route. No regrets.
What software version are you running?
 
My M3 is a 2019.. so it's 2.5 years now plus however long it say around waiting to be installed/delivered etc. Anyways.. I opened a ticket with Tesla for a proactive replacement explaining I was going on a 2K road trip in March and I wanted to proactively replace it instead of trying to do it on the road trip. I just got the verification for the appointment.. Est. is N/C.. covered by warranty. :) After hearing all the stories about lack of customer service, I was expecting to pay my 85 + dollars. So a pleasant surprise.

Will be interested to see if they really replace it proactively (when the car hasn't given any warning) at no charge. I haven't heard of them doing that. Please report back.
 
They replaced it today without any fuss. No charge. The tech even calibrated my windows which had some alignment issues a few days ago which he said was a sign that the battery was failing even though it didnt actually trigger a fault alert.
 

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Can you replace the standard 12v with any 12v bought from somewhere else?
From what I have found, it needs to be a Group 51R battery that is rated "Deep Cycle". Non deep cycle batteries have good start power but are not could for long periods of use and recharge. The factory 12volt does seem to have higher available CCA over others I've found. I'm not sure an AGM battery would be a good idea as I think charging voltages are slightly different and the onboard BMC will interpret charge differences as a fault and toss out messages.
 
From what I have found, it needs to be a Group 51R battery that is rated "Deep Cycle". Non deep cycle batteries have good start power but are not could for long periods of use and recharge. The factory 12volt does seem to have higher available CCA over others I've found. I'm not sure an AGM battery would be a good idea as I think charging voltages are slightly different and the onboard BMC will interpret charge differences as a fault and toss out messages.
From what I've measured in my Model 3 since last fall, Tesla does not really deep cycle the battery. I've only seen about 6% max discharge on my 12v battery before the car charges it up again. So my recommendation would be to replace it with any group size 51R battery because 6% depth of discharge is perfectly fine for even a starting battery. I would still try to find one that is maintenance free and had a pretty on the side to vent gases into a hose.
 
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ANYTHING the car does when parked uses 12v. So, sentry mode, summon standby, always connected… would all seem to cause higher 12v recharge cycles. Plus I suspect a lot of the features use 12v even when driving, as Something has to convert HV battery to a “usable” voltage for things like computer, cameras.,,
No, when the car is "awake", the HV battery and DC-DC is engaged - there is no load on the 12V, in fact it's being charged. When Sentry mode is on, the HV battery and DC-DC are on and powering the car - that's why Sentry mode drains the battery so much.

The car will sleep for 24-48 hours when idle and wake up for an hour or two to top off the 12V battery. I'm guessing that the car monitors the 12V battery voltage and when it gets low enough, it wakes up to charge it.

I was warned of a deteriorating battery and it was about a month before it was replaced under warranty. I think the warning software has been improved.
Yes - the battery in my '18 3 LR RWD died earlier this month (or at least the car though it was dying). What I found is that the car would no longer sleep and stayed away during this time - presumably it does this because it's afraid that putting any load on the battery will result in the 12 V dropping too low and not being able to wake back up.

Scheduled service via the app for after lunch the next day and they swapped it out in 30 minutes.

I am curious about running a lithium battery, though. I'm pleased to see that Tesla switched to lithium for the 12V. Fully charging a lead-acid takes a while (the 1-2 hours) - recharging the 12V lithium could be done in 30 minutes, saving on vampire drain over time.
 
Watching this thread with interest. Wonder if the Model 3 with go li-ion as I believe facelifted S and X are. Weird that there's no rhyme or reason to it. I'm hoping if be able to blag a new battery before the 4 year warranty is up😀. My worry is my nearest SC is about an hour away, although I'm covered in their mobile region, both at home and at work so worst case just book it for during work. This is in UK btw, not sure if our warranties are different.
 
Watching this thread with interest. Wonder if the Model 3 with go li-ion as I believe facelifted S and X are. Weird that there's no rhyme or reason to it. I'm hoping if be able to blag a new battery before the 4 year warranty is up😀. My worry is my nearest SC is about an hour away, although I'm covered in their mobile region, both at home and at work so worst case just book it for during work. This is in UK btw, not sure if our warranties are different.

Done,
 
TL;DR I replaced mine proactively at the 2 year mark. $100 is worth the peace of mind, hands down. I also keep an A23 battery under the tow hook cover and an emergency jump starter in the front trunk. No way I’m taking chances on this, especially given the remote locations I drive to.
 
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