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

[dmurphy]

When it comes to my dollars it's always a decision based on risk reward and for me I'm proactive when it comes to the car.

I'm usually(!!) right there with you, but on this battery front, I'm almost of the "let's take a ride and see where we land" mindset. Not really sure why - I spend more than $85 on ridiculous things all the time.

My Model 3 is just over 3 years old and 41k miles. It's been ridden hard and put away wet. I don't baby the car by any means - just drive it like I would any other car. And yet, somehow, it still survives the abuse... Part of me wants to see just how long I can ride the 12V battery; the other part of me wants to replace it proactively.

Maybe I'll just buy a battery and keep it on a battery tender so I can do a quick swap when the time comes......

 

[texas_star_TM3]

part of the reason why I don't replace a 12V battery proactively under 4 yrs (and *within* the warranty) ... maybe if there are enough claims and roadside assistance deployments (on Tesla's dime) ... Tesla will figure out how to use a much more reliable 12V battery. I never had *any* 12V battery in prior vehicles fail in under 4-5 yrs or less than 50k miles. Proactively swapping a battery every 2yrs seems crazy...

 

[TulsaCoker]

I did after 3 1/2 years while I was getting the computer upgrade done. cheap only $114

 

[IROAR]

Sorry if this has already been stated but my M3 gave me message that the battery was going bad, before it went bad, enabling me to schedule the mobile ranger for a replacement under warranty. With an ice vehicle, the first warning you get is when the car won't start. No need to be proactive

 

[RayK]

How often did you replace batteries with your ICE cars. I replaced every 4-5 years routinely to avoid issues, even though I had no problems.
Your car with 23.5K miles in 4 years, average 6K/yr does not see a lot of trips and charging cycles. I'd replace it to be on safe side for next 4 years. No reason to wait for a failure.

Vehicle before the Tesla was a 2000 BMW 323i. Had it for 18 years and I believe I replaced the battery twice, so about 5 years on average. However, one of those replacements was probably due to the fact that an adapter for an aftermarket CD changer was not powering down when it should have. That caused the battery to die a couple of times when the car sat for a week.

 

[TulsaCoker]

No need to be proactive

disagree.

 

[PianoAl]

part of the reason why I don't replace a 12V battery proactively under 4 yrs (and *within* the warranty) ... maybe if there are enough claims and roadside assistance deployments (on Tesla's dime) ... Tesla will figure out how to use a much more reliable 12V battery. I never had *any* 12V battery in prior vehicles fail in under 4-5 yrs or less than 50k miles. Proactively swapping a battery every 2yrs seems crazy...

I'm 100% with you on letting Tesla get the message, but you may pay a high price for giving them some feedback.

 

[gearchruncher]

It will tell you state of charge.

Voltage will tell you state of charge, but not state of health. You know the battery is 87% charged, but not if it's degraded so it only has 5Ah left when it was 40Ah originally. This is why a AAA battery and D battery have the same voltage- you can't detect capacity this way.

You'd have to monitor voltage over time and check for how quick it discharges, but that would also require a well known discharge curve. It's also completely thrown off by all the charging the DC-DC does.

 

[texas_star_TM3]

I'm 100% with you on letting Tesla get the message, but you may pay a high price for giving them some feedback.

oh yeah. I have no longer trips planned until end of this year... and the trips which i do have planned are weekend trips to large metro areas. If it get stranded there with a dead battery i would expect roadside assistance to come by fairly quickly.

 

[M3NYCFanboy]

My car is at the 2 year mark, and since I am planning a trip to AZ next month, I decided to go ahead and schedule a mobile service appointment for a proactive battery replacement. Got a call from the service advisor confirming that I wanted the replacement, since they didn’t see any errors. I confirmed, and the appointment is set for next week. Cost before tax will be about $117.

He also mentioned that they would be updating the battery to the Lithium ion battery (he sad LED battery, but I think he meant Li-on, or maybe I misheard him). Will update back next week when I have it installed, but I didn’t realize that they were installing lithium batteries now.

Interesting, I tried to do the same for model 2018 model 3 before a road trip a couple of months ago. They said mine was not compatible with it. What year is your model 3?

 

[RayK]

Interesting, I tried to do the same for model 2018 model 3 before a road trip a couple of months ago. They said mine was not compatible with it. What year is your model 3?

I believe that this was a misunderstanding. Tesla service tech meant "lead", as in lead-acid battery, not LED (pronounced the same and not as individual letters).

ref: "Proactive" 12v battery replacement - good idea or overkill? and the next couple of posts

 

[gearchruncher]

There's a lot of stories in the past of 12V batteries dying suddenly, but Tesla has significantly changed how they detect failures and behave once detected. Now, once the car notices a bad 12V battery, it will run the whole car off the DC-DC and slowly drain the HV battery (no more than sentry does though). This advanced checking is actually causing problems with some of the aftermarket batteries.

I'd say a proactive replacement is way overkill nowadays. My battery is 4 years old and is still very healthy (as checked off-car by actually fully measuring the capacity of the battery)

 

[gearchruncher]

Your car with 23.5K miles in 4 years, average 6K/yr does not see a lot of trips and charging cycles.

Cycles on the battery in a Tesla have almost nothing to do with your mileage. It's always cycling this battery when the car is not on, in fact the more you drive it the less it uses the battery.

The real question is how much you use sentry as that stops using the battery as well at the expense of draining your main battery much quicker.

 

[brkaus]

There's a lot of stories in the past of 12V batteries dying suddenly, but Tesla has significantly changed how they detect failures and behave once detected. Now, once the car notices a bad 12V battery, it will run the whole car off the DC-DC and slowly drain the HV battery (no more than sentry does though). This advanced checking is actually causing problems with some of the aftermarket batteries.

I'd say a proactive replacement is way overkill nowadays. My battery is 4 years old and is still very healthy (as checked off-car by actually fully measuring the capacity of the battery)

I'm starting to agree. My Model 3 first 12v lasted 2 years. Second one is now on 2 years and still going. No big trips planned, so I'll let it ride and hope for a warning over a failure.

My march 2017 S has a different type of 12v, but car hasn't issued any warnings on that yet.

 

[Theone8181]

But I still don't get why they aren't dieing on ice cars quickly, you're running the same ancillaries soife should br similar.

 

[brkaus]

But I still don't get why they aren't dieing on ice cars quickly, you're running the same ancillaries soife should br similar.

Tesla took advantage of the large battery backup that frequently comes on to recharge the 12v and has a much higher load on the battery, specifically when the car is “off”.

My truck can sit unused for months and still start.

I’ve let our leaf sit for a month and it worked.

The 12v monitor on my Tesla shows it tops off daily, and that is reinforced by the multiple miles of range lost per day on the main pack.

 

[SilverString]

Tesla took advantage of the large battery backup that frequently comes on to recharge the 12v and has a much higher load on the battery, specifically when the car is “off”.

My truck can sit unused for months and still start.

I’ve let our leaf sit for a month and it worked.

The 12v monitor on my Tesla shows it tops off daily, and that is reinforced by the multiple miles of range lost per day on the main pack.

How are you monitoring the 12v battery?

 

[SilverString]

Sorry if this has already been stated but my M3 gave me message that the battery was going bad, before it went bad, enabling me to schedule the mobile ranger for a replacement under warranty. With an ice vehicle, the first warning you get is when the car won't start. No need to be proactive

In general I would agree, but in some situations I feel it's worth it if for no other reason than peace of mind. I am about to embark on a multi thousand mile road trip into the mountains and places where even mobile service could be a few days away. My car has over 50K miles and is covered under the Tesla extended warranty which has a $200 deductible, so the cost to do it now and pay full price was only $8 more than if I waited for it to fail. I do not want to get stranded thousands of miles from home so $8 was an easy choice.

 

[android04]

How are you monitoring the 12v battery?

This is what I've been using since August of last year to monitor mine https://smile.amazon.com/gp/aw/d/B07CTKYFTG

 

[Theone8181]

Tesla took advantage of the large battery backup that frequently comes on to recharge the 12v and has a much higher load on the battery, specifically when the car is “off”.

My truck can sit unused for months and still start.

I’ve let our leaf sit for a month and it worked.

The 12v monitor on my Tesla shows it tops off daily, and that is reinforced by the multiple miles of range lost per day on the main pack.

I didn't think sentry and all the smart features used the 12v, I just assumed it was stuff like a/c that used it although I've not looked into it in much detail. I'd much rather not bother with a 12v at all and just use the main battery like they did in the roadster.