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Signs of Battery Failure

There's no sense in trying to fix something that ain't broke.

Tesla batteries (all batteries) degrade with age, and we should not be unreasonable in expectations. Some of us put more stress on the batteries than others.

Still, batteries do fail. I want to know the signs.

I want to get your comments on my list of signs that the battery is declining in an abnormal way. Also, I include items which in my opinion are NOT signs of battery decline. So here is my list.

1) People seem very interested in how much energy the car uses per mile, but I believe this has very little to do with your battery condition. If my car used to run at 275 per mile and now it runs at 380, maybe I have a problem with my motors, or tires, or I have gained weight, or it's hotter, or my wheels are out of alignment. Any of these will use up the battery more quickly, but not because it's a degraded battery. To get good answers about the battery, I think maybe you need to be sure the conditions in which you are running your car are the same in these ways. Before thinking about the battery be sure these things have not changed between your experiments.

2) Having dealt with 1 above, suppose your range traveled by your odometer is very much less than your range traveled according to the "miles left" display on your dash. For example, if I charge to say 284 miles (86% of my 330 original capacity) and then I drive until I have 184 miles left, so 100 miles traveled, but by the odometer I have traveled only 70 miles, that might be a red flag. However, again a warning about number 1 above: Your car's range by the display will not be accurate if you are carrying your 400 pound horses in back seat uphill on a 100 degree day while stopping overnight halfway.....UNLESS you used the same conditions when the car was new! The key here is this: devise a test that you can repeat easily.....AND be sure your car is dealing with same conditions, inside and outside.

3) Suppose your maximum battery capacity declines substantially. Unfortunately, Tesla may hide this by putting an invisible cushion at the top so that you can still "charge to full capacity" even if the battery has degraded. Still, if your max has declined so substantially that in no longer charges to the original max, that might be a sign, but only if it is extreme. I wish somebody could tell me how much decline in my max is enough to discuss it with Tesla service. I also wish it did not degrade the battery to test it by fully charging it! (Maybe only do this once every few months....) In my own case, my battery no longer fully charges to 333 the way it did the first time. But it still charges to 228.

Anyway, those are my thoughts. What are yours. I am particularly interested in some tests which can help me know if my battery is doing ok or should definitely get me to check with Tesla.

Cheers,
gScargo

PS If my battery catches fire, do you think that might be a sign? ( ! ! )
 

Tam

Well-Known Member
Nov 25, 2012
11,606
10,673
Visalia, CA
...tests...

There are third-party apps to measure the voltage of your main battery modules such as:

Using TM-Spy to see Model S data.

screenshot_2016-02-21-09-29-24-png.112144


As you can see those 96 bricks above are pretty even with the maximum difference of 4 mV.
 
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Rocky_H

Well-Known Member
Feb 19, 2015
8,365
10,760
Boise, ID
Usually a problem sign: if your rated miles level at a certain fill point has consistently been within 1-2 of a certain level and then you find that suddenly one day it's 20+ lower. We've seen that several times over the years, where one of the bricks within the pack has gone bad, so it lost that large chunk of range suddenly.

But that is way different than: "My rated miles is only XXX, but when it was new 3 years ago, it had XXX." Gradual declines of 10-20 miles over years are not the same thing and aren't usually a failure.
 
There's no sense in trying to fix something that ain't broke.

Tesla batteries (all batteries) degrade with age, and we should not be unreasonable in expectations. Some of us put more stress on the batteries than others.

...

In my own case, my battery no longer fully charges to 333 the way it did the first time. But it still charges to 228.
THat's a lot of degradation in range, if it's real. You've lost about 33% of capacity, which would qualify you for a Telsa warranty repair if your battery is less than 8 years old. Is it?
 
THat's a lot of degradation in range, if it's real. You've lost about 33% of capacity, which would qualify you for a Telsa warranty repair if your battery is less than 8 years old. Is it?
OOPS Error. Very Sorry! I meant max was no longer 333, it was now 328. Yep, 228 would have been pretty bad! My max stated range dropped very slightly as corrected above (as of two months or so ago). But in the hot Austin summer I was getting very roughly 60 actual odometer miles when I used up roughly 100 miles of stated range (like from 280 remaining down to 180). I thought maybe something was interfering with my battery efficiency --my car has needed zero maintenance for almost a year. Maybe the battery heating-cooling system should be serviced.....Very irritating to have such a reliable car!
 
OOPS Error. Very Sorry! I meant max was no longer 333, it was now 328. Yep, 228 would have been pretty bad! My max stated range dropped very slightly as corrected above (as of two months or so ago). But in the hot Austin summer I was getting very roughly 60 actual odometer miles when I used up roughly 100 miles of stated range (like from 280 remaining down to 180). I thought maybe something was interfering with my battery efficiency --my car has needed zero maintenance for almost a year. Maybe the battery heating-cooling system should be serviced.....Very irritating to have such a reliable car!
Well, that's a big difference!

There are many reasons why 100 odometer miles don't reduce battery meter capacity by 100 miles. Chief among them is vehicle speed. The Tesla battery meter assumes (on the Model3) 150 Wh/km (about 240 Wh/mile) when it gauges remaining miles of battery charge. Driving faster than 100 km/h (60 mph) will use more battery capacity per 60 miles than assumed by the battery meter. This is not a battery efficiency issue, just physics: all cars will use more fuel at higher speeds due to air drag, which is proportional to speed to the power 3. Secondly is battery temperature. Driving on a cold battery will use more battery capacity per km (or mile) than a warm battery. Given that your stats don't state any of these conditions, and likely weren't kept identical (did you measure them?), no conclusion about your battery condition is possible.
 
There are third-party apps to measure the voltage of your main battery modules such as:

Using TM-Spy to see Model S data.

screenshot_2016-02-21-09-29-24-png.112144


As you can see those 96 bricks above are pretty even with the maximum difference of 4 mV.
Tam,

I need some help. I’m currently on a road trip, and something odd is happening. My 2014 Model S 60 is showing 162 miles of rated range at 94% charge. When I was leaving the last supercharger the percentage would start at 80% and then a couple of miles down the road it did a sharp drop to 72%. I usually keep the car display on percentage since I live in NYC and never drive many miles in a day. The car has 50,000 miles on it. Would you consider taking the car in to be tested? How easy is it to test the battery myself to see if something is wrong?

I’m asking because of your post and you may be able to point me in the right direction.
 

Tam

Well-Known Member
Nov 25, 2012
11,606
10,673
Visalia, CA
...80% and then a couple of miles down the road it did a sharp drop to 72%...

I am no expert but this is what I think:

The battery State of Charge can easily fluctuate such as being cooling down.

80% after a drive and when it cools down in winter, you can easily get 72%.

However, that is not your scenario because you were driving and it shouldn't drop from 80% to 72% in just a few miles and I assume in the same road conditions and not climbing uphills.

On the other hand, the battery gauge does attempt to measure your State of Charge in real-time and it can update what it finds instantly such as you mentioned 80% in one instant and 72% in the next.

After ruling out all factors that could eat up 8% in a few miles such as speed, acceleration, temperature, heater, uphills... it might be because of your battery.

If you are handy, it's easy to follow instructions to buy adapters & use TM-Spy to measure your battery in detail.

It could be that your main pack is "un-balanced" as evidenced by a big difference in voltage that you can read from the graph and you can easily identify which of the 96 bricks are those.

Sometimes a deep discharge from 100% to near depletion then immediately recharge back up to 100% (then make sure to drive back down to 90%) might help.

If not, your car might still continue to duplicate the same scenario, 80% now then suddenly 72% then next again for no reason.

A sudden drop in the range is not a problem as long as you have plenty of range left to get home.

The problem with a bad battery is it gets worse, more often and more drastic to the point that you won't have the range to get home.

Thus, you should have Service Center take a look and fix it under the main battery warranty pre-emptively so you won't be stranded on the road.

The problem with the current policy of cost-cutting, Tesla might only want to look at your battery problem after you are stranded and not pre-emptively. But that's too pessimistic, let's hope for the best!
 
I am no expert but this is what I think:

The battery State of Charge can easily fluctuate such as being cooling down.

80% after a drive and when it cools down in winter, you can easily get 72%.

However, that is not your scenario because you were driving and it shouldn't drop from 80% to 72% in just a few miles and I assume in the same road conditions and not climbing uphills.

On the other hand, the battery gauge does attempt to measure your State of Charge in real-time and it can update what it finds instantly such as you mentioned 80% in one instant and 72% in the next.

After ruling out all factors that could eat up 8% in a few miles such as speed, acceleration, temperature, heater, uphills... it might be because of your battery.

If you are handy, it's easy to follow instructions to buy adapters & use TM-Spy to measure your battery in detail.

It could be that your main pack is "un-balanced" as evidenced by a big difference in voltage that you can read from the graph and you can easily identify which of the 96 bricks are those.

Sometimes a deep discharge from 100% to near depletion then immediately recharge back up to 100% (then make sure to drive back down to 90%) might help.

If not, your car might still continue to duplicate the same scenario, 80% now then suddenly 72% then next again for no reason.

A sudden drop in the range is not a problem as long as you have plenty of range left to get home.

The problem with a bad battery is it gets worse, more often and more drastic to the point that you won't have the range to get home.

Thus, you should have Service Center take a look and fix it under the main battery warranty pre-emptively so you won't be stranded on the road.

The problem with the current policy of cost-cutting, Tesla might only want to look at your battery problem after you are stranded and not pre-emptively. But that's too pessimistic, let's hope for the best!
Thank you. That is very helpful. I’ll try all options and let you know how it turns out.
 
I am the third owner of my 2015 Model S 70D. I've had the car since July 2020. At that time, a full charge yielded 238 miles. Now a full charge yields around 220 miles. I typically charge to around 80% but do occasionally have to charge to 100% for long daily commutes without the ability to charge (where I'd arrive home with 10-15% remaining). Whenever I charge to (or near) 100% I always time it so I immediately start driving (i.e., never leave it for hours with >90% charge). So, I while I do occasionally have to charge it to near full, I do so in a thoughtful way to minimize impact on the battery. (this has been maybe once a month since I owned the car).

Since I was not the original owner of the car, I don't have those initial data points of what the original "full charge" mileage was on this vehicle. I am in the last year of the battery and motor warranty and want to figure out how much mileage this car SHOULD have at this point on a full charge. In other words, what should the original mileage have been? What SHOULD it be now? At what "Full charge" mileage threshold would it be reasonable to talk to Tesla about a warranty replacement of the battery? Bonus question: are there suggested ways to have this conversation with Tesla that would be more likely to result in a battery replacement?
 

Tam

Well-Known Member
Nov 25, 2012
11,606
10,673
Visalia, CA
...what the original "full charge" mileage was on this vehicle...
What counts is the EPA number. For yours, it's 240 miles.
...I am in the last year of the battery and motor warranty and want to figure out how much mileage this car SHOULD have at this point on a full charge. In other words, what should the original mileage have been?
240
What SHOULD it be now?
The warranty does not cover the degradation of your battery. For Model 3 and Y, it's 70%. 70% of 240 for your car is 168
..At what "Full charge" mileage threshold would it be reasonable to talk to Tesla about a warranty replacement of the battery?
When your battery can no longer hold a charge. It's a battery failure. Your warranty does not cover degradation even when its capacity is lower than 70% (unlike the 3 and Y).

Bonus question: are there suggested ways to have this conversation with Tesla that would be more likely to result in a battery replacement?
Battery failure. Not battery degradation below 70%.
 
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Rocky_H

Well-Known Member
Feb 19, 2015
8,365
10,760
Boise, ID
At what "Full charge" mileage threshold would it be reasonable to talk to Tesla about a warranty replacement of the battery?
As @Tam described, and I am concurring with, this is not a thing at all. Your car is a 2015, and back then, the wording of the warranty very specifically EXCLUDED any degradation of capacity from normal use from being covered by the warranty in any way.
 

ucmndd

Well-Known Member
Mar 10, 2016
9,115
17,688
California
I am the third owner of my 2015 Model S 70D. I've had the car since July 2020. At that time, a full charge yielded 238 miles. Now a full charge yields around 220 miles. I typically charge to around 80% but do occasionally have to charge to 100% for long daily commutes without the ability to charge (where I'd arrive home with 10-15% remaining). Whenever I charge to (or near) 100% I always time it so I immediately start driving (i.e., never leave it for hours with >90% charge). So, I while I do occasionally have to charge it to near full, I do so in a thoughtful way to minimize impact on the battery. (this has been maybe once a month since I owned the car).
220 for a 70D is actually very good. The car was rated at 240 miles when new. ~8% observed degradation in 7 years is quite normal, on the good side of normal even.
At what "Full charge" mileage threshold would it be reasonable to talk to Tesla about a warranty replacement of the battery?
None, your car has no warranty for battery degradation.
Bonus question: are there suggested ways to have this conversation with Tesla that would be more likely to result in a battery replacement?
No.
 
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