decrease in distance for full battery charge

decrease in distance for full battery charge

I'm curious about the deterioration of MX batteries. We purchased the long range battery on our 2016 MX, which was 257 miles at that time. As recommended, we only fully charge it when taking long trips. On Friday the battery would only charge to 239 miles. We have less than 24,000 miles on our 26 month old MX. Are other owners experiencing similar decrease in battery power?

dhelmly | 30 July 2018

I have a 2016 as well (Vin 0040xx) and had an issue of charging to 242 . I had Tesla check and they got it back to 254-255 which is consistent now for several months.

davidahn | 30 July 2018

Sounds like a big drop (7%) for 24,000 miles and 26 months, IMHO. My MS has dropped from 270 to 256 (5.2%) over 70K miles and 3 years.

Have you tried recalibrating your pack? Some owners have reported increased rated range after fully discharging and then charging to 100%. According to Tesla, this doesn't actually change your available range, only the BMS's estimate of your range when 100% charged. Some discourage this recalibration as unhealthy for your battery, but most state charging to 100% is not harmful as long as you run it down immediately.

CKS | 30 July 2018

Thank you for your recommendations.

mathwhiz | 30 July 2018

This issue has probably been discussed more than any other... I wrote this post awhile ago, but it still holds value today:

"Actual degradation of a battery pack's range capability is extremely difficult to measure. And although yes, a pack is thought to normally degrade perhaps 1-2% in the first year or so, actual degradation will then progress very slowly and evenly through the remainder of the useful life of the pack. However, what owners will perceive as pack "decay" as you put it, is actually caused by an inherent error in the vehicle's ability to calculate a pack's remaining energy (rated mile range capability). This error is usually most pronounced in vehicles that are charged daily, but not driven enough to permit state-of-charge (SOC) to get out of the top half of capacity much, resulting in a higher than desired average SOC.

Rated Miles is a calculation that indicates the current *estimated* condition of the battery pack (based on the EPA 5- cycle Range test standard *for vehicles sold in the U.S.)... The only confusion I know of is the fact that the Rated Miles reading isn't perfect. It's intended to show the current condition of the battery pack, minus degradation due normally to age. But, the calculation can get 'outta whack' over time, indicating less Rated Miles than actually exist. The reasons for this are thought to be related to pack atrophy through lack of exercise through its capacity of range (a simplification from my understanding of the cause). When this happens, it is possible to reacquaint the pack with its actual current capacity by allowing the pack SOC to get low, over a period of days, and then recharge it to normal... Depending on how much error has accumulated, this process may need to be repeated.

These are the subjects (actual pack degradation and the Rated Miles calculation) about which there can be confusion and needless worry."

For this reason, you might consider using % charge rather than rated miles display.

CKS | 1 August 2018

Thank you, math whiz, for your information, but since we don't drive many miles each day, we only charge about once a week to around 215 (85% of original full battery) and let it run down under 50 miles before charging again. We have lost 7% of our battery life in 2 years/24,000 miles. We were not able to drive more miles than indicated after charging. I will try to let SOC stay low for a few days, but I'm not optimistic. I emailed Tesla last week and I haven't heard back.

mathwhiz | 2 August 2018

Interesting... The question that presents right away is, where did the 24k mi come from? I guess you must accumulate them on periodic extended trips rather than daily driving?

Also, from your description, you've implemented the inverse behavior from most owners. That is, rather than daily charging and periodically dealing with battery 'recalibration' as davidahn puts it, you chronically avoid charging until down to around 50 mi SOC... Which leads me to wonder, was this particular protocol recommended by anyone at Tesla? I mean, I'm well familiar with doing this as the exception, not the rule. But using this as a normal procedure makes me wonder what the long term effect on the pack will be.

In any case, I’m of the opinion that your extraordinary battery pack degradation isn’t mostly actual, but for some unexplained reason your BMS is losing the ability to properly gauge range.

I wish I could be more helpful, but clearly the answer to this is something that Tesla needs to provide.

Not sure how you posed the question to Tesla Support but, in the event of an unsatisfactory answer after exhausting local resources, I’d recommend escalating the issue to the executive care group via your MY TESLA account.

Good luck.

davidahn | 2 August 2018

I know many of us developed the habit of charging full and fully discharging back in the nickel-cadmium days, and I still can't seem to get away from it even with my lithium ion devices like my shaver. But with a high ticket item like the Tesla, I listen to the experts: keep the SOC as close to 50% SOC as possible. I try to keep it between 80% and 20%, sounds like you're not too far off from that, 15-85%. I might try a calibration cycle, and if that doesn't help, take it to your SC.

Starlifter | 3 August 2018

been driving a 90D since dec 2016. initially rated at 256 I believe. anyway for what it's worth - we have done 5 long range trips and occasional day trips where we fully charge. Only once or twice have we allowed the range to go below 30 miles remaining. we typically charge every day to 210 miles and discharge down to 100 miles remaining. I live in Pennsylvania (for weather and driving condition comparison).

fully charged the other day for a day trip to 255 miles. Our battery is holding it's max capacity as far as I can tell.

I make no claims to technique nor a plan to preserve battery life - just describing my charging habits and the results I've seen. Your mileage may pun intended.

mathwhiz | 4 August 2018

Not to nitpick davidahn but, I'd make one little modification to your recommendation... To keep the *average* SOC as close to 50% as possible. Oh and, for the battery pack, variety is the spice of life. '-)

CKS | 9 August 2018

Thank you all for responding to my issue.
To Mathwhiz, yes, I was told by a Tesla rep that I should charge to 80% and recharge when it falls to 20%. Maybe that was bad info.
Star lifter: - I'm jealous you can charge to 255 miles on your 2016 90D. Although we purchased ours on 5/16, I would love to get over 250..
I received a discouraging email from Tesla today telling me 7% loss in two years isn't out of the ordinary. Everyone who has responded has only lost 2-3% so I am not satisfied. I tried discharging to 6 miles then fully charging, today 237 was my limit. 20 mile loss in 26 months/24,000 miles. Not good!

Redmiata98 | 9 August 2018

My P90L 2016 has about a 6% loss which is what I have understood as the normal range loss for my model. So, the 2 or 3% being reported here is unusual. If you are at 7%, that is close to normal. Mine levelled off after the first year and has remained consistent since then. When I got mine the guidance was always charge to 90% and leave it plugged in but only go to 100% when you plan to use it for longer trips. No minimum charge was given but I rarely get it below 12% and when it does I bring it back to 90% within an hour or so. I use the supercharger a lot. | 10 August 2018

I think @mathwhiz is correct. The decline in the estimated rated range for a given % charge level is more likely an artifact of the calculation of rated range by the car and less due to actual degradation of the Li-ion cells, although the, over time, there will be some degradation to be sure. Unless there is a sudden, substantial drop in apparent capacity, I wouldn't worry about a slow decline in apparent rated range. My AP1 X90D with 20K miles reports 219 miles of rated range for 90% SOC where it reported about 230 when new.ntwo years ago. Not a problem.

davidahn | 10 August 2018

@mathwhiz, not to nitpick your nitpicking... (haha) but repeatedly charging to 100% and discharging to 0% would follow your recommendation (average of 50% SOC) while being not so great for the batteries. :)

mathwhiz | 11 August 2018

Wow, that be order of magnitude nitpick. '-)

justin.rogers77 | 13 August 2018

Just bought a CPO 32k mile early 2016 X P90DL to replace a model 3 that was totalled, been concerned about degradation. 90%=210 miles. Does seem really low. Our MS 75D 26k miles has more range at that charge. Not keen on the idea of doing the full to empty charge thing but did let the service center know and am awaiting a response.

Redmiata98 | 13 August 2018

Remember that the 100% for the P90 is 250 vs 257 for the 90. That would put your ideal 90% at 225. Given that, you are at about 6.3%. P90 is probably a 2016 vintage similar to mine and same mileage. Mine usually settles at 211 for 90% but does fluctuate between 210 and 214. The 90 was discontinued and replaced with the 75 which appears to be holding its charge better, but then the 75s are not as old as the 90s. You also do not know how the battery was charged or discharged so getting your service center to dig up the charge history is prudent.

vprelovac | 14 August 2018

I am seeing similar degradation as op. Its 2 year 75D with 23k miles and it charges to about 226 miles (original 237). I also employ a similar pattern - I would typically charge it once week (not a lot of driving typically). And for some reason idea of putting it on charge every day (even if used just 20-30 mi) does not seem right And then few times a year we would do a massive roadtrip (just came from a 6000 mi one). I rarely charged it to 100% perhaps 20-30 times in total in two years.

Now the 90% charge is about 203-204 (was 215 original) mi and is approaching psychological barrier of 200.

PXChanel | 2 September 2018

Yes, MX90D, delivered 6/17 now after 2 y 2 mo, it charges to 243 at 100% instead of 257, and 224 at 90%, which is less than 233 it charged to at 90% in the beginning.

PXChanel | 2 September 2018

Yes, MX90D, delivered 6/17 now after 2 y 2 mo, it charges to 243 at 100% instead of 257, and 224 at 90%, which is less than 233 it charged to at 90% in the beginning.

jjgunn | 2 September 2018

I think we're beginning to see why Tesla stopped making/selling the 90 kw batteries. I haven't heard of the 100's having this much of a drop other than the display mis-reporting the actual range correctly. It's just a software thing they're working on.

Triggerplz | 2 September 2018

@Pxchanel delivered on 6/17 and had it 2 years 2 months that must be one of those back to the future models :-)

PXChanel | 2 September 2018

@Triggerplz You’re right, makes no sense. Correction: delivered in 6/16.

Triggerplz | 2 September 2018