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Signs of Battery Failure

Scargoes

New Member
Jul 8, 2019
3
1
Austin
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
9,421
8,601
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.
 
  • Informative
Reactions: bhzmark

Rocky_H

Well-Known Member
Feb 19, 2015
6,762
8,340
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.
 

Tessaract

Member
Aug 12, 2019
337
338
Ottawa
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?
 

Tam

Well-Known Member
Nov 25, 2012
9,421
8,601
Visalia, CA
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 depends on what car.

Only Model 3 has 70% capacity warranty, not S, not X.
 
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Reactions: Rocky_H

Scargoes

New Member
Jul 8, 2019
3
1
Austin
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!
 

Tessaract

Member
Aug 12, 2019
337
338
Ottawa
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.
 

robertmanning

Member
Dec 8, 2018
143
115
New York
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
9,421
8,601
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!
 

robertmanning

Member
Dec 8, 2018
143
115
New York
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.
 

amiral_sub

Member
Sep 20, 2019
139
90
Bordeaux, France
my hv battery just failed. The SOC dropped from 80% to 42% while the car was parked. It displayed strange errors. Several hours later I wanted to drive it, unable to drive, the park brake stopped the car. The car was sent to the SC, HV battery failure
 

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