Battery Fuse replacement warning

[sean_az]

About 2 weeks ago, a warning appeared on my console with the following message, which would not go away under any circumstances:

Battery fuse requires replacement soon
OK to drive - Schedule service

Not knowing what it was, I did some searching. There's not a whole lot of info about what it is or what it does. Some say it's a non-powered fuse and has to get replaced with powered fuse. Some mix it with Pyro fuse which after much research, seems to be a different thing.

I scheduled service through the app and Tesla's Mobile Service showed up after a couple of days. Technician said that it's just a reconfiguration of the system and nothing needs to be replaced. He plugged in his laptop to the car, went into "Service Plus" mode and cleared the warning. But he did say that I wasn't even supposed to see that message. Don't know exactly what that means, but probably something in the last OTA update flipped a flag on an internal config and it has to be changed locally by a technician. Just a guess on my part. I found just 1 picture of the "Service mode" on Model S which said that "Battery fuse needs to be replaced by x date", somewhat like an expiration date, but there was no other explanation.

All is well now, but I wanted to share with you that if you see this annoying message, nothing needs to be replaced and the issue will go away after a 5 minute visit by a technician.

 

[DerbyDave]

Don't know the year of your car, but early Teslas thru 2015 or 2016 had a pyro fuse that would blow using a 10 year lifetime lithium battery, much like a smoke detector battery. Newer cars do not require an internal battery. You have reached the end of life for that pyro fuse. It is for your safety. It should be replaced, just like a smoke detector.

 

[vcor]

Don't know the year of your car, but early Teslas thru 2015 or 2016 had a pyro fuse that would blow using a 10 year lifetime lithium battery, much like a smoke detector battery. Newer cars do not require an internal battery. You have reached the end of life for that pyro fuse. It is for your safety. It should be replaced, just like a smoke detector.

Accurate, but a poor choice of words. The Pyro fuse will not blow at the end of life of its internal small lithium battery. It will no longer work as a fuse, such that if an overload occurs (which is a super rare event), it will not disconnect quickly. Something else will melt instead, but would likely cause other damage if it needed to be triggered.

There is a software timer that should bring up the "Time to Replace" message when the battery nears its expected end of life. There is no ability to monitor the pyro fuse's battery voltage, so it's a design estimate of when the battery likely needs replacement.

It sounds like the timer was improperly triggered, and that is why the tech could just reset the timer.

The new design used for the last several years no longer needs a lithium battery and should last the life of the car.

 

[DerbyDave]

Some clarification to your post. The pyro fuse also blows in a severe accident to try to prevent the HV battery fires. The newer pyro fuse no longer uses an internal battery:

"This new "self-powered hybrid pyro fuse" gets juice from "the current flowing directly through the fuse" and does not need to be replaced unless it deploys for any reason, but that is also expected. The surprise here is having a fuse powered by its own cell."

You may get a few extra years out of an old Lithium battery powered fuse, just like if you don't replace your 10 year smoke detectors immediately when the expiration date is reached.. Both, however, could pose a danger of fire for either your car, or your house, if not properly maintained and increase the threats of danger to you and your family. Hopefully, you will luck out in case of a disaster.

 

[taimurasad]

About 2 weeks ago, a warning appeared on my console with the following message, which would not go away under any circumstances:

Battery fuse requires replacement soon
OK to drive - Schedule service

View attachment 967891

Not knowing what it was, I did some searching. There's not a whole lot of info about what it is or what it does. Some say it's a non-powered fuse and has to get replaced with powered fuse. Some mix it with Pyro fuse which after much research, seems to be a different thing.

I scheduled service through the app and Tesla's Mobile Service showed up after a couple of days. Technician said that it's just a reconfiguration of the system and nothing needs to be replaced. He plugged in his laptop to the car, went into "Service Plus" mode and cleared the warning. But he did say that I wasn't even supposed to see that message. Don't know exactly what that means, but probably something in the last OTA update flipped a flag on an internal config and it has to be changed locally by a technician. Just a guess on my part. I found just 1 picture of the "Service mode" on Model S which said that "Battery fuse needs to be replaced by x date", somewhat like an expiration date, but there was no other explanation.

All is well now, but I wanted to share with you that if you see this annoying message, nothing needs to be replaced and the issue will go away after a 5 minute visit by a technician.

Which year car do you have?

 

[sean_az]

Which year car do you have?

My Model S is 2018

 

[sean_az]

Don't know the year of your car, but early Teslas thru 2015 or 2016 had a pyro fuse that would blow using a 10 year lifetime lithium battery, much like a smoke detector battery. Newer cars do not require an internal battery. You have reached the end of life for that pyro fuse. It is for your safety. It should be replaced, just like a smoke detector.

Thanks for the info. Super helpful. My Model S is 2018. I did find some YouTube videos and went down the rabbit hole of what it is and what it does, which validates what you say. Newer model don't seem to have this issue any more since it looks like Tesla redesigned the circuit board to manage this issue electronically without batteries.

One video mentioned that the software might get triggered when the battery pack is retrofitted or changed. This did happen to me. In late 2021, when Tesla replaced my HV Battery Pack (my car was in the shop for over 60 days). Thank goodness the warranty covered it. That may or may not be the factor, but I thought to mention this as well.

 

[LongMutts]

Don't know the year of your car, but early Teslas thru 2015 or 2016 had a pyro fuse that would blow using a 10 year lifetime lithium battery, much like a smoke detector battery. Newer cars do not require an internal battery. You have reached the end of life for that pyro fuse. It is for your safety. It should be replaced, just like a smoke detector.

Thank you. This makes sense in my case because the date of the warning turning on coincides with 6 months away from the 8th birthday of the car (aka end of the battery warranty). I keep reading all of this contrasting information and experiences in and around the necessity of the battery fuse replacement and the suspiciousness of the warning itself. Thanks for this.

 

[mongo]

Accurate, but a poor choice of words. The Pyro fuse will not blow at the end of life of its internal small lithium battery. It will no longer work as a fuse, such that if an overload occurs (which is a super rare event), it will not disconnect quickly. Something else will melt instead, but would likely cause other damage if it needed to be triggered.

I've read that the current limit to blow the fuse lowers as the battery voltage drops. The vehicle software reduces maximum current based on projected trip point to prevent non-fault activation, but the car will get slower.
I don't know whether the end point is refusal to move, fuse trip, or power limited car and no fuse function.

 

[Tracy Anderson]

Got my warning back at the beginning of August. Set up the service appointment for 09/21. Got the repair estimate of $501.60 which also includes a diagnostic fee… yet I’m taking it in to them because of the code.. but whatever. Not only that, but Tesla will not honor the 3rd party bumper to bumper warranty I purchased with the car. I love the car, but this has to be the absolute worst service I’ve ever had. And with more people buying Tesla’s from 3rd party dealers, they really should rethink this. Then again, they probably just don’t care.

 

[DerbyDave]

Your third-party warranty will likely pay, you just need to get the estimate and forward to them. Once they approve the work, have Tesla do, pay for it, and send the proof of payment and receipt to the insurance. Easy-peasy!

 

[teddytoons]

Got my warning back at the beginning of August. Set up the service appointment for 09/21. Got the repair estimate of $501.60 which also includes a diagnostic fee… yet I’m taking it in to them because of the code.. but whatever. Not only that, but Tesla will not honor the 3rd party bumper to bumper warranty I purchased with the car. I love the car, but this has to be the absolute worst service I’ve ever had. And with more people buying Tesla’s from 3rd party dealers, they really should rethink this. Then again, they probably just don’t care.

Thanks. I just got the same warning on my 2017 MS 90D. I just wanted to see what I was in for. I may come back to his post and post my own results.

 

[vcor]

I've read that the current limit to blow the fuse lowers as the battery voltage drops. The vehicle software reduces maximum current based on projected trip point to prevent non-fault activation, but the car will get slower.
I don't know whether the end point is refusal to move, fuse trip, or power limited car and no fuse function.

No. There is no software control of the HV pyro fuse. It's a self-contained unit with only two connections - the HV in and out. If the current through the device exceeds the design threshold, it blows the connection. There is no ability to monitor voltage or be externally commanded by software.

The advantage of this design is it can be quite precise. Typical mechanical-only fuses are not very precise. The pyro fuse allows more current up to the limit and then has a hard trip point. The end result is you can safely use more current from the battery without the risk of a meltdown or other damage that could occur with a mechanical fuse of the same current handling capacity.

 

[DerbyDave]

In an accident, the pyro fuse is blown when the airbags are deployed in a serious accident. How is this controlled if not by sensors?

 

[RHTrio]

About 2 weeks ago, a warning appeared on my console with the following message, which would not go away under any circumstances:

Battery fuse requires replacement soon
OK to drive - Schedule service

View attachment 967891

Not knowing what it was, I did some searching. There's not a whole lot of info about what it is or what it does. Some say it's a non-powered fuse and has to get replaced with powered fuse. Some mix it with Pyro fuse which after much research, seems to be a different thing.

I scheduled service through the app and Tesla's Mobile Service showed up after a couple of days. Technician said that it's just a reconfiguration of the system and nothing needs to be replaced. He plugged in his laptop to the car, went into "Service Plus" mode and cleared the warning. But he did say that I wasn't even supposed to see that message. Don't know exactly what that means, but probably something in the last OTA update flipped a flag on an internal config and it has to be changed locally by a technician. Just a guess on my part. I found just 1 picture of the "Service mode" on Model S which said that "Battery fuse needs to be replaced by x date", somewhat like an expiration date, but there was no other explanation.

All is well now, but I wanted to share with you that if you see this annoying message, nothing needs to be replaced and the issue will go away after a 5 minute visit by a technician.

Dear Sean,

Received the same message. Tesla service is giving me an estimate of $551.53 (out of warranty) but with no explanation of what this is!

Thoughts?

Much appreciated,

Rob

 

[DerbyDave]

Rob, the collection above shows that the older pyro fuses have a lithium battery, much like a smoke detector. It has a 10 year estimated life. When the time is up, you are warned to change it out.

 

[mongo]

In an accident, the pyro fuse is blown when the airbags are deployed in a serious accident. How is this controlled if not by sensors?

That's the 12V pyro fuse, the pack fuse has no external connections.

 

[mongo]

No. There is no software control of the HV pyro fuse. It's a self-contained unit with only two connections - the HV in and out. If the current through the device exceeds the design threshold, it blows the connection. There is no ability to monitor voltage or be externally commanded by software.

The advantage of this design is it can be quite precise. Typical mechanical-only fuses are not very precise. The pyro fuse allows more current up to the limit and then has a hard trip point. The end result is you can safely use more current from the battery without the risk of a meltdown or other damage that could occur with a mechanical fuse of the same current handling capacity.

Yes, a self contained unit whose trigger threshold lowers as the battery is depleted below the level of the stable reference + headroom.
The vehicle software has a rough model of the discharge curve and will reportedly limit drive unit current to below that calculated value to avoid tripping it.

 

[Tracy Anderson]

Your third-party warranty will likely pay, you just need to get the estimate and forward to them. Once they approve the work, have Tesla do, pay for it, and send the proof of payment and receipt to the insurance. Easy-peasy!

I actually submitted the estimate to my 3rd party warranty company last week. However, it's still pending approval due to the fact the repair estimate calls this part a fuse, but it's not listed in the manual as a maintenance item, so I think it's confusing my warranty folks. The fact that Tesla won't even talk to my warranty company probably doesn't help matters much either. I am hoping it gets approved, but we will see.

 

[DerbyDave]

The decision could go either way, as the fuse has an expendable item (a battery), that usually is not covered like other expendable items: batteries, tires, brakes, rotors, etc.