Battery degradation question

[moswissa]

I know there are tons of threats of people worrying about battery degradation as the range appears to decrease over time.

My MYP has 4500 miles on the Odometer. It started off at 281 miles of range but now I barely get to 269 at full charge. I’m only opening this thread because I find it interesting that Tesla advertises 291 miles for the performance model. Me and my wife both drive this car on sport mode but we aren’t necessarily racing the entire time but do you like to give it some torque, so can someone explain their opinion on why or what causes the range to drop.

 

[DaveORD]

There are some other threads that talk about how range is related to how much you charge and drain the battery so the car can better estimate. Search for those, I think it was recommended that you drive it down quite a ways like 10-20 percent, then charge to 90 and do that 2-3 times for the car to better learn the capacity of the battery and range. Or something like that. If you are constantly charging to 80 and only going down to 60 or 70 before charging again, that may work against you, estimate lower range. What you are doing is unknown to me, how low before charging and what you end up charging to, but you can get the gist of it, the battery needs a couple of big swings to train your car what it has. Find that thread, it has more info.

 

[Tam]

...tons of threats...

Yes, this has been repeated over and over again when I first got my 2012 Model S 8 years ago and it has not stopped.

I guess Tesla's answer to that is: It guarantees 70% capacity so it will cover you when yours will be below 70%.

Your battery gauge is affected by your charging habit but that doesn't necessarily that the range has been reduced.

So, as @DaveORD mentioned: What is your charging habit like? Daily or less frequently? What's the percentage set at routinely?

Back to the battery gauge, as mentioned above, it can gradually calculate incorrectly to display the lesser range when there's no actual range decrease in your battery at all.

That means it should say 100%=291 and if there's nothing changed, it should not say 100%=269.

You can reset its calculation by starting a good charging habit by setting your charger at 90% and charge at least daily. It might take days or weeks for the recalculation.

The way your battery gauge works is: It wants to know when your battery is 0% so it can mark that as 0 miles and when it's 100% so it can mark that as 291 miles. However, 0% or 0 miles is not good for your battery. Prolonged 100% or 291 miles is not good for your battery either. So Tesla makes a compromise and sets the algorithm assuming that owners practice daily charges at 90%.

Even after you reset the calculation, you might actually have a reduction in the range:

291-269= loss of 22 miles

or

22/291 = 7.56%

If you are not happy with that number, you can make an appointment to the Service Center. Most likely, they would do a diagnosis over the air and tell you it's within their specifications (that means it has not gone below 70% yet!).

 

[Zoomit]

drive this car on sport mode but we aren’t necessarily racing the entire time

How you drive the car is not relevant.

why or what causes the range to drop.

Tesla Official Statement on Range

See also: How to take care of your battery without stressing: advice for new owners.

 

[Flybuddy]

I had owned a 2nd gen Volt for 4 years before the Tesla. The estimated range had nothing to do with charging habits. You didn't have the option of reducing from 100% charge short of pulling the plug. The mileage displayed was solely a result of actual mileage obtained during previous trips. I wonder if the Tesla estimated range also take this into account?

 

[Zoomit]

I had owned a 2nd gen Volt for 4 years before the Tesla. The estimated range had nothing to do with charging habits. You didn't have the option of reducing from 100% charge short of pulling the plug. The mileage displayed was solely a result of actual mileage obtained during previous trips. I wonder if the Tesla estimated range also take this into account?

It does not.

Here is the equation.

More details here: Battery Management System - What I Learned At Tesla Service Center

 

[Tam]

...It started off at 281 miles of range but now I barely get to 269 at full charge...

Now, that @Zoomit mentioned. Are those numbers from the battery gauge or you used to be able to actually drive 281 miles and now only get 269 miles on the trip odometer?

For actual traveling miles (trip odometer), you can manipulate that number by altering EPA parameters such speed, wind, elevation, temperature, car accessories such as HVAC...

So, to beat 291 EPA number, I can drive really slowly and those people are called "hypermilers". They can easily drive 500 miles in 1 charge but of course with very impractical slow speed.

The opposite is true if I am a drag racer, use HVAC...

 

[moswissa]

Yes, this has been repeated over and over again when I first got my 2012 Model S 8 years ago and it has not stopped.

I guess Tesla's answer to that is: It guarantees 70% capacity so it will cover you when yours will be below 70%.

Your battery gauge is affected by your charging habit but that doesn't necessarily that the range has been reduced.

So, as @DaveORD mentioned: What is your charging habit like? Daily or less frequently? What's the percentage set at routinely?

Back to the battery gauge, as mentioned above, it can gradually calculate incorrectly to display the lesser range when there's no actual range decrease in your battery at all.

That means it should say 100%=291 and if there's nothing changed, it should not say 100%=269.

You can reset its calculation by starting a good charging habit by setting your charger at 90% and charge at least daily. It might take days or weeks for the recalculation.

The way your battery gauge works is: It wants to know when your battery is 0% so it can mark that as 0 miles and when it's 100% so it can mark that as 291 miles. However, 0% or 0 miles is not good for your battery. Prolonged 100% or 291 miles is not good for your battery either. So Tesla makes a compromise and sets the algorithm assuming that owners practice daily charges at 90%.

Even after you reset the calculation, you might actually have a reduction in the range:

291-269= loss of 22 miles

or

22/291 = 7.56%

If you are not happy with that number, you can make an appointment to the Service Center. Most likely, they would do a diagnosis over the air and tell you it's within their specifications (that means it has not gone below 70% yet!).

My habit is charging daily to 90% and usually runs down to about 60-70%. Elon said best way to maintain battery is to always keep it plugged so that’s why.

 

[EnrgyNDpndnce]

My habit is charging daily to 90% and usually runs down to about 60-70%. Elon said best way to maintain battery is to always keep it plugged so that’s why.

Read the articles as others have mentioned but it sounds like your calculation would benefit from a couple of deep cycles. IE drive it close to zero remaining (get under 10% for sure) then charge to 100% (and immediately go for a drive, not good to let the car sit at 100% too long).

Also important to remember your displayed range and ACTUAL range are often different numbers. If your displayed range has noticeably decreased over a short period of time it’s likely a BMS calculation issue and doesn’t really impact your actual range.

 

[Zoomit]

Read the articles as others have mentioned but it sounds like your calculation would benefit from a couple of deep cycles. IE drive it close to zero remaining (get under 10% for sure) then charge to 100% (and immediately go for a drive, not good to let the car sit at 100% too long).

Unfortunately, if you immediately go for a drive, it would likely be a wasted effort and needlessly put the battery through a deep discharge cycle.

None of us here have the full details about how the car calculates that range estimate, but the best information I’ve found is the text from the Service Manual I linked to previously. It’s a few years old now and Tesla could have certainly changed the algorithm. Also, it was written for Model 3, though I expect it applies to Model Y just the same.

Caveats aside, here is the relevant paragraph:

The pack shunt is used to count amp-hour over a certain amount of time. That value and on the delta SOC for that amp-hour amount is used to determine CAC. [JH5] This calculation is done whenever there is a drive or charge cycle however values are only stored when the calculation is deemed accurate. There are many complex parameters that factor into the accuracy of that number, and the HVBMS decides when the number is accurate enough to update CAC. One of these parameters is rest time before and after the drive/charge cycle. Notice in the figure above that the SOC was flat for a long time before and after the drive, this results in the most accurate voltage/SOC measurement which makes the CAC calculation accurate. Therefore in a worst case example, if a driver constantly charged and drove without ever letting the vehicle rest at a fixed SOC, then CAC algorithm will not update during that time.

In summary, the car needs to rest before the drive for “a long time” to provide the most accurate measurement for the range calculation. Based on the graph, that rest duration might need to be 30-60 minutes or possibly even longer.

 

[Klau2]

I know there are tons of threats of people worrying about battery degradation as the range appears to decrease over time.

My MYP has 4500 miles on the Odometer. It started off at 281 miles of range but now I barely get to 269 at full charge. I’m only opening this thread because I find it interesting that Tesla advertises 291 miles for the performance model. Me and my wife both drive this car on sport mode but we aren’t necessarily racing the entire time but do you like to give it some torque, so can someone explain their opinion on why or what causes the range to drop.

The upcoming 2020.28.2 update will change your range to 291 full, that will be in line with what tesla advertiser on their site. you should see your estimate range increase also after the update.

2020.28.2 (Software Update) | Teslascope

 

[moswissa]

The upcoming 2020.28.2 update will change your range to 291 full, that will be in line with what tesla advertiser on their site. you should see your estimate range increase also after the update.

2020.28.2 (Software Update) | Teslascope

I upgraded to this software yesterday and my range shows 268 on a full charge. So I doubt that’s true

 

[Wennfred]

I upgraded to this software yesterday and my range shows 268 on a full charge. So I doubt that’s true

Battery calibration, take it down to 10% and back to 100% 3x. If this doesn’t fix it, submit a service ticket. That’s a big drop in range for only 4500 miles, my Stand Range Plus sitting happy at 90% stayed steady for a whole year and one of the Patches smokes it, lost 10-12 miles over night.

The picture below shows the immediate hit after the Update. I will also look for and post a video from Kim of “Like Tesla” she had this same problem and they took the car in and had it rebalanced, she regained her range back.

 

[Wennfred]

 

[Zoomit]

Battery calibration, take it down to 10% and back to 100% 3x. If this doesn’t fix it, submit a service ticket. That’s a big drop in range for only 4500 miles, my Stand Range Plus sitting happy at 90% stayed steady for a whole year and one of the Patches smokes it, lost 10-12 miles over night.

The picture below shows the immediate hit after the Update. I will also look for and post a video from Kim of “Like Tesla” she had this same problem and they took the car in and had it rebalanced, she regained her range back.

View attachment 566339

It's important to note that recalibrating the BMS does not change the ACTUAL battery capacity and thus does not change the ACTUAL range the car can drive. It's also different than brick balance, which can change the battery capacity. The LikeTesla video conflates these two.

Doing a few full discharges, like you suggested, would only help the BMS calibration and increase the indicated range. It would not affect the actual distance the car could travel.

 

[Wennfred]

It's important to note that recalibrating the BMS does not change the ACTUAL battery capacity and thus does not change the ACTUAL range the car can drive. It's also different than brick balance, which can change the battery capacity. The LikeTesla video conflates these two.

Doing a few full discharges, like you suggested, would only help the BMS calibration and increase the indicated range. It would not affect the actual distance the car could travel.

Good point, Thanks!

Fred

 

[TDI Gromby]

Maybe I missed in the thread, but is there a way, even with aftermarket software, to view the total amp hour capacity calculated by the BMS? I come from the Nissan LEAF world where an app called LeafSpy easily allowed to view this info. Also gave you remaining amp hour capacity as a percentage of new amp our capacity. IE, my battery is now a say 95% capacity left due to degradation.

 

[Wennfred]

Maybe I missed in the thread, but is there a way, even with aftermarket software, to view the total amp hour capacity calculated by the BMS? I come from the Nissan LEAF world where an app called LeafSpy easily allowed to view this info. Also gave you remaining amp hour capacity as a percentage of new amp our capacity. IE, my battery is now a say 95% capacity left due to degradation.

There is one that shows a ton of stats, Bjorn out of Norway uses it. Let me find you a video on it.

Scan My Tesla

Fred

 

[moswissa]

It's important to note that recalibrating the BMS does not change the ACTUAL battery capacity and thus does not change the ACTUAL range the car can drive. It's also different than brick balance, which can change the battery capacity. The LikeTesla video conflates these two.

Doing a few full discharges, like you suggested, would only help the BMS calibration and increase the indicated range. It would not affect the actual distance the car could travel.

hmm So you’re telling me that the actual range won’t get affected, only the displayed Range will? So I might as well just switch to percentage mode and drive the car and forget about it huh, but in all honestly I just want to make sure my Tesla isn’t defective

 

[Zoomit]

hmm So you’re telling me that the actual range won’t get affected, only the displayed Range will? So I might as well just switch to percentage mode and drive the car and forget about it huh, but in all honestly I just want to make sure my Tesla isn’t defective

Forum members post almost daily with the same concern, but I don't recall hearing of someone with a defective battery pack. I'm sure there's a few out there but I would say it's a very low probability that your pack is defective. Likewise, if it was, I wouldn't expect the failure mode to be catastrophic, meaning the capacity would likely just keep degrading but it wouldn't leave you stranded on the side of the road.