Battery degradation

[Richgoogol]

I've had my car for roughly 7 months now and it has about 12,000km. Today I have charged my X75 to 100% for the first time and it only got to 370km on a full charge. That's about 3% degradation already. Is this normal?

 

[int32_t]

Are you looking at Rated Range (the EPA-based estimate) or the other estimate (I forget what it's called exactly)?

I don't have a Tesla yet so maybe I'm not the best person to answer, but there is soooo much magic that goes into the range estimate, I wouldn't hang my hat on that 3% number unless you'd done the 100% charge the day you bought it and wrote down what number the magic produced then.

Also, this post might be helpful -- the graph shows that 3% degradation can happen, but then you'd be at the bottom of the bell curve, statistically.

 

[Troy]

Hi. At 12,000 km the average capacity is 97.8% but 97% is perfectly normal. Degradation is faster at the beginning but then slows down. The chart below is from this battery survey. If you enter your data, you can then go to the charts page and select your username and it will show your entry in a different color on the chart. This way you can easily see how it compares to the trend line.

If people from the USA or UK enter their data and select their username on the charts page, the chart will switch from km to miles.

Btw, you might want to submit new entries once in a while so you can see how things change over time. A new entry every 8.000-12.000 km (5,000-7,500 mi) is a good idea. Next time you charge to 100%, could you test if changing the range mode setting instantly increases the displayed range like in this video?

@int32_t, when I clicked on your link I saw the old version of this chart that I posted two years ago. At that time, there were too few entries and the trend line was less clear. It was interesting to see how things have changed since then.

 

[int32_t]

Hi. At 12,000 km the average capacity is 97.8% but 97% is perfectly normal. Degradation is faster at the beginning but then slows down. The graph below is from this battery survey. If you enter your data, you can then go to the charts page and select your username and it will show your entry in a different color on the graph. ...@int32_t, when I clicked on your link I saw the old version of this graph that I posted two years ago. At that time, there were too few entries and the trend line was less clear. It was interesting to see how things have changed since then.

Aha, the expert has landed! I have bookmarked the link so I'll always have up-to-date data.

That's interesting, actually. Numbers to remember: 8% degredation after 1/4 of a million kms!

 

[Richgoogol]

Are you looking at Rated Range (the EPA-based estimate) or the other estimate (I forget what it's called exactly)?

I don't have a Tesla yet so maybe I'm not the best person to answer, but there is soooo much magic that goes into the range estimate, I wouldn't hang my hat on that 3% number unless you'd done the 100% charge the day you bought it and wrote down what number the magic produced then.

Also, this post might be helpful -- the graph shows that 3% degradation can happen, but then you'd be at the bottom of the bell curve, statistically.

Not really sure but I'll double check tomorrow. Unfortunately I did not charge it to 100% on the day I took delivery. I was a bit worried that there could be some faulty batteries since I have only really taken ownership not for too long. But from looking @ the graph it seems like it could happen. Thanks for your help!

 

[Richgoogol]

Hi. At 12,000 km the average capacity is 97.8% but 97% is perfectly normal. Degradation is faster at the beginning but then slows down. The chart below is from this battery survey. If you enter your data, you can then go to the charts page and select your username and it will show your entry in a different color on the chart. This way you can easily see how it compares to the trend line.

If people from the USA or UK enter their data and select their username on the charts page, the chart will switch from km to miles.

Btw, you might want to submit new entries once in a while so you can see how things change over time. A new entry every 8.000-12.000 km (5,000-7,500 mi) is a good idea. Next time you charge to 100%, could you test if changing the range mode setting instantly increases the displayed range like in this video?

@int32_t, when I clicked on your link I saw the old version of this chart that I posted two years ago. At that time, there were too few entries and the trend line was less clear. It was interesting to see how things have changed since then.

Wow that's very informative. I love it! Great to know that I'm not an outlier. I'll definitely input my data. Seems like your are a pro at this, I have one more question to trouble you with. When I charged to 100% today, the dotted line appeared like in the winter time, is it because the battery is cooling itself? I guess it's safe to assume that it's not good for the battery at all to charge to 100%

 

[Troy]

Hi. There is a thread here about the dotted line. In this case, it means regen is not available because you already have 100% charge and there is nowhere else to put the energy that would come from regen.

As for charging to 100%, the consensus is that charging to 100% is not a problem but leaving the battery at 100% or 0% is. In addition, be aware that never dropping to 0% or near 0% will cause inaccurate range displays over time, maybe after 6 months or so because the computer will have difficulty guessing how much energy the battery holds. There is no exact measure. The displayed range is always an estimate and the car constantly calculates energy coming in and going out but these calculations become inaccurate over time if you never fully or almost fully discharge.

 

[animorph]

Keep in mind software updates may also change the displayed rated range. I "lost" about 6 miles at 90% charge in displayed range recently. Warned about it in the release notes. Kind of hard to track degradation unless you correct for that. Other than that I haven't noticed any degradation, always hitting the same 90% rated range.

Edited to add: charging (slowly) from 90% to 100% helps rebalance the battery and may recover some of your degradation.

 

[int32_t]

So why are you answering instead of leaving it to actual Tesla owners who know something about this?

Dood! I'm just trying to be helpful. I didn't reply to the exclusion of all others -- we can all offer something, and others did indeed lend their own valuable voices to the conversation. Besides, I have more than a passing interest in lithium batteries and SoC algorithms and have researched the topic extensively (and found that it's best to sum it all up as magic). And my post wasn't altogether unhelpful (if I do say so myself) since I included a link to some "hard facts," to quote Charles Dickens.

And if I had not posted, Troy would not have pointed out that my go-to data was significantly out of date, and the next person who asks about degradation (on the forum or in real life) would have received an equally out of date answer based on a severely limited sample size, since that's all I would have been aware of. So regardless of how you look at it, posting my perhaps ill-informed reply was for the better.

I'm not sure why I feel the need to justify myself. <shrug>

Not really sure but I'll double check tomorrow. Unfortunately I did not charge it to 100% on the day I took delivery. I was a bit worried that there could be some faulty batteries since I have only really taken ownership not for too long. But from looking @ the graph it seems like it could happen. Thanks for your help!

Oh -- speaking of faulty batteries, I believe cell balancing only occurs if left plugged in to something better than 120V (like HPWC or J1772 or whatever) for several hours, with the charge limit set to 100%. Try that if you have access to that kind of power; you might find your range increases slightly. Unbalanced cells aren't faulty, just slightly weaker than the others so that they become slightly undercharged over multiple charge/discharge cycles. Fully charging and then waiting some time gives the battery management circuitry a chance to top up the weaker cells so that they match the stronger ones and get back in balance again, which improves the performance of the entire pack.

 

[gaswalla]

You really need to charge to 100 three consecutive days and then measure for any degradation. At this point the stated range is the result of inaccurate algorithms as well and lack of a fully balanced battery. It seems like this is the first time you have done a 100 charge, so the battery is definitely out of balance.
Please try it - I promise your range will increase.

 

[Richgoogol]

You really need to charge to 100 three consecutive days and then measure for any degradation. At this point the stated range is the result of inaccurate algorithms as well and lack of a fully balanced battery. It seems like this is the first time you have done a 100 charge, so the battery is definitely out of balance.
Please try it - I promise your range will increase.

Thank you. I'll most definitely try it out.