Is my battery degrading faster than usual ?

[bigbfan]

Hi All,
I have a S75 that has about 14K miles on it and is about 11 months old.My avg wh/mile about 350 wh/mile. i love in San Francisco Bay Area and park my car in my garage. I have always followed Tesla’s charging recommendations: charge to 90% , after the commute (40 miles total) , plug it in again at home.
I supercharge about once every 6-7 weeks probably. I hardly ever get my car to lower level.. I recall the lowest once was at 40 miles said left.
I recently , just to check my batteries degradation, charged to 100%. Attached is the screenshot after I had used 52% of that charge (As you can see remaining charge is 48%). You can also see how many kWh I have used : 31.8kWh. So 52% of my battery charge equates to 31.8kWh, does that mean I have only ~ 61kWhView attachment 357729 of battery left? This is S75.
I have gone twice to the Service Center , but got standard replies that my battery is fine (which it clearly isn’t if I am not wrong).
Please help. Should I go and make a stink at the Service Center : I feel like there is something wrong

 

[acoste]

I think this is a software issue. You shouldn't lose 16% in such a short time. The usable capacity when new is 72.6kWh.

Maybe just wait for a software update or try to rebalance the batteries.

Maybe try this:
Tesla Bjorn measured his new battery with 0.1kWh error using his method.

 

[bigbfan]

I think this is a software issue. You shouldn't lose 16% in such a short time. The usable capacity when new is 72.6kWh.

Maybe just wait for a software update or try to rebalance the batteries.

Maybe try this:
Tesla Bjorn measured his new battery with 0.1kWh error using his method.

how do I rebalance the batteries ?

 

[acoste]

he has a video for everything

 

[bigbfan]

he has a video for everything

Sorry i dont get it. I think he did say his was unbalanced, but he didnt say how he balanced it. Maybe I missed it, can you say ? Also mine *did* charge to full 100%.

 

[ucmndd]

Don't try to extrapolate range or battery capacity based on incomplete charges or consumption shown in the instrument cluster, particularly if you often hover between a narrow range like 90-70%.

What does your car charge to at 100%? That's really the only meaningful metric without having access to the service functions of the car.

 

[acoste]

Sorry i dont get it. I think he did say his was unbalanced, but he didnt say how he balanced it. Maybe I missed it, can you say ? Also mine *did* charge to full 100%.

One part of it is charging the battery up to 100% patiently (meaning wait until the charge current reduces to nothing) once or twice. And the other issue is that the electronics miscalculate the numbers for the 0%. I would try to drain the battery down to 0% as close as possible. Stay safe though.

Watch the relevant videos on Bjorn's site.

 

[csanders90D]

Based on that picture, you used 52% of the battery over multiple trips. Any power that your car used between trips (running computers, heating/cooling battery, etc.) will decrease the % charge on your battery but won't be reflected on the "Since last charge" trip odometer. For better accuracy, measure the % battery used over 1 trip. Or switch your battery display to rated miles instead of % and see what it charges to.

 

[bigbfan]

Based on that picture, you used 52% of the battery over multiple trips. Any power that your car used between trips (running computers, heating/cooling battery, etc.) will decrease the % charge on your battery but won't be reflected on the "Since last charge" trip odometer. For better accuracy, measure the % battery used over 1 trip. Or switch your battery display to rated miles instead of % and see what it charges to.

Hmm... I do have a good assessment of how much my battery is drained on non-movable operations. Plus I don't use heat/cool much (I am in SF BAY area) so I am not sure computer and heat will chew so much of battery (I monitor tht vampire drain and its not that much to show a 16% battery degradation in less than year. In my humble opinion. )

 

[bigbfan]

Hmm... I do have a good assessment of how much my battery is drained on non-movable operations. Plus I don't use heat/cool much (I am in SF BAY area) so I am not sure computer and heat will chew so much of battery (I monitor tht vampire drain and its not that much to show a 16% battery degradation in less than year. In my humble opinion. )

Here is another data point.
Today I charged to 75%. See attached picture. I consumed 23% of the battery which equated to 14.3 kWh. That adds up to the battery at 61kWh. That’s about 16% degradation in 11 Months.

 

[TexasEV]

Here is another data point.
Today I charged to 75%. See attached picture. I consumed 23% of the battery which equated to 14.3 kWh. That adds up to the battery at 61kWh. That’s about 16% degradation in 11 Months.

No, because that's assuming the state of charge estimate is accurate and we know it's often not. The only data points that matter are range at 100% charge.

 

[bigbfan]

No, because that's assuming the state of charge estimate is accurate and we know it's often not. The only data points that matter are range at 100% charge.

Hmmmm.. so its general knowledge that the state of charge estimate is not accurate often, while the range at 100% is ? isn't the range also based on a very complex formula that has to do with one's driving habits and conditions ? My 100% charge was 232 miles for my ModelS 75.

 

[TexasEV]

Hmmmm.. so its general knowledge that the state of charge estimate is not accurate often, while the range at 100% is ? isn't the range also based on a very complex formula that has to do with one's driving habits and conditions ? My 100% charge was 232 miles for my ModelS 75.

No. Rated range is the range on the EPA test cycle. Period. It has nothing to do with driving habits. Search here for hundreds if not thousands of posts explaining rated range and issues with estimates of state of charge.

 

[ucmndd]

My 100% charge was 232 miles for my ModelS 75.

So you’ve lost about 7%. More or less normal. As I said above, this is the best and only measurement of degradation without access to the battery management system.

 

[Todd Burch]

I was talking to a Tesla tech friend the other day about this. About 2 months ago the indicated range on my S dropped by about 10 miles over a short period of time.

He said that Tesla introduced a software bug a while back that was resulting in incorrect range readings. He said that they’re still working it but it’s a software problem, and only a problem with the indication (not a real battery problem).

If you are treating the battery well as you say you are, your real degradation will be quite a bit less than 7%.

 

[Brass Guy]

Aside from the rated range and percentage being a sort of guestimate, according to this article
https://electrek.co/2016/12/14/tesla-battery-capacity/
(calculations by well respected member @wk057)
the 75 battery pack initially has 68.8 kWh of usable capacity.

 

[Electric700]

Hmmmm.. so its general knowledge that the state of charge estimate is not accurate often, while the range at 100% is ? isn't the range also based on a very complex formula that has to do with one's driving habits and conditions ? My 100% charge was 232 miles for my Model S 75.

So if you've charged to 100% and let the charge complete (then drive it right away for better battery health), and you're seeing 232 miles, then that's an almost 7% range loss from the car's new rated range of 249 miles, which is based on the EPA rating. From here on you may notice minimal to no degradation, as many others have. I believe the biggest drop is normally seen within the first 1 - 2 years, then it levels off.

Just keep to the Tesla recommendations of charging to a maximum of 90% for normal use, and perhaps 100% once a year to be sure the batteries are balanced or if needed for trips, and you should be fine.

Also one other tip, if you need to leave the car for a few days, consider setting the charge level to 55% and enable Energy Saving, with Always connected off.

 

[bigbfan]

So if you've charged to 100% and let the charge complete (then drive it right away for better battery health), and you're seeing 232 miles, then that's an almost 7% range loss from the car's new rated range of 249 miles, which is based on the EPA rating. From here on you may notice minimal to no degradation, as many others have. I believe the biggest drop is normally seen within the first 1 - 2 years, then it levels off.

Just keep to the Tesla recommendations of charging to a maximum of 90% for normal use, and perhaps 100% once a year to be sure the batteries are balanced or if needed for trips, and you should be fine.

Also one other tip, if you need to leave the car for a few days, consider setting the charge level to 55% and enable Energy Saving, with Always connected off.

Thanks! You guys have all been very helpful. On what is the best level to charge and discharge , I have been religoulsy charging to 90% and then after it drops to 70% (my daily commute), charge it again overnight to 90%. However i hear that also there are many schools of thoughts on this too. I read recently some posts, plus Elon himself saying on Twitter, that for the best longetivity from your pack, refreshing the batteries around 50% is the way to go as a best practice. So if your daily back and forth commute uses 20% (mine does), then its best to charge to 70%, and then let it drain to 30% where 50% is the mid point.

I wonder what is this groups thoughts on that ?

 

[TexasEV]

No. There’s more to life than the absolute maximum longevity of the battery, long after you no longer have the car. Have you RTFM? Tesla has been emphatic about this from day 1– plug it in whenever you can. Do not wait until the charge gets low. Frequent smaller charges are better. Let the battery management system manage the battery. Etc etc.

Google “A connected Model S is a happy Model S.”

 

[TexasEV]

Rules for stress-free Tesla ownership:
1. Set charge level to 90%.
2. Plug in every evening when you get home.
3. Never think about the battery again.

Actually there is one exception to these rules. When you are going on a trip, increase the charge to 100% in the morning while you’re getting ready to leave. Then set it back to 90% when you get home. Don’t worry if you forget, the car will remind you if it’s still set at 100% after three days.

Most importantly, just enjoy your car.