Battery Strategy and Degradation at 10k Miles

[gad1976]

I read and read and read about everyones battery degradation so I adopted a battery charging strategy in hopes of being "that guy" who defied the odds. Seems I was unsuccessful. . Oh well, I tried. Here is how things stand after 10k miles.

I drive a MYLR with a rated range of 330 miles.

I've owned the car for 8 weeks and have been averaging 1250 miles per week. My average will fall, but not by a lot. Long term I believe I'll average about 800 miles per week.

When I get home I usually have less than 20% battery. I immediately charge to 50% well the battery is still warm. Then I let it rest at 50% until the next time I need to travel. Usually less than 36 hours. I will then set it to be charged by my departure time. Occasionally I can leave the house with only 70% charge, but most of my trips I need 90-100% charge to avoid using a supercharger. Usually I can get home without supercharging, but sometimes I need to stop for a 10 minute charge. So I am actively trying to keep the charge below 80%. When it does get a full charge I drive immediately and get it back to 80% or below in about an hour. I don't charge over 80% at super chargers typically. So I would tell you that the car has had a charge of more than 80% for only 25 hours of its life.

I did take a 3,000 mile vacation that was exclusively superchargers, but other than thank I charge mostly at home.

So, as best I can tell, here is what it has done to my battery (it's not as good as I hoped, but I'm still satisfied, and I LOVE the car.)

Testify says I've lost 3.88% or about 13 miles. Up until about 8,000 miles it looked like I was beating "the system" but then shortly after that I dropped down to where everyone else was.

If anyone is interested in the charge levels this screen grab shows how many times I charged to various percentages.



And lastly, the breakdown of home charging vs supercharging. This shows 38% at superchargers, but that will go down. That was skewed by the 3,000 mile vacation. Going forward I estimate I'll supercharge less than 15%. 85% at home. Total cost of electricity for 10k miles was $641.18. Supercharging was WAY more expensive than charging at home. Just in case there are any newbies out there that expect to supercharge for free (oddly that's the most frequent comment I get about superchargers "oh, they aren't free?)



For those of you who know "batteries" does degradation come from time? Miles? Usage? In other words, have I sped up the degradation by so many miles in such a short amount of time, or is that irrelevant?

p.s.

I run the IOS App STATS. It gives similar information. It puts me at a range of 319 miles or a loss of 11 miles range. A loss of about 3.33%

 

[Zoomit]

When it does get a full charge I drive immediately

It's possible your BMS has a poor calibration on the full battery capacity due to your anxiety about not leaving it at high SOC. To help the BMS calibration, do a full charge from a resting very low SOC to 100% and let it rest (2 hours sleeping). Cycling this a few times may be required. Each cycle may degrade the battery by ~0.05% [source, reference thread]--It will be ok, you and your car will survive!

For those of you who know "batteries" does degradation come from time? Miles? Usage?

Yes, and...

From:

 

[rjpjnk]

I've been using that TeslaFi app for over two years now and I find that battery capacity chart fluctuates a lot. I also was briefly above average, and then way under average, and then eventually back up to average. Not sure what to make of it, but I would say try not to take the numbers too seriously. and don't worry even if it tells you your battery is the worst it's ever seen out of 400 other cars. It's just not that reliable short term.

 

[Big Earl]

Drive more, worry less.

 

[gad1976]

It's possible your BMS has a poor calibration on the full battery capacity due to your anxiety about not leaving it at high SOC. To help the BMS calibration, do a full charge from a resting very low SOC to 100% and let it rest (2 hours sleeping). Cycling this a few times may be required. Each cycle may degrade the battery by ~0.05% [source, reference thread]--It will be ok, you and your car will survive!


Yes, and...

View attachment 966370
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So, do you think my strategy of charging to 50% as soon as I arrive home “while the battery is still warm” and then setting it to finish charging/preconditioning to 80, 90, or 100% by my daily departure time the next day, doesn’t really help lengthen my battery life?

I get the feeling that many people just feel “it is what it is” enjoy it. Drive. Don’t worry.

I’m mostly good with the “don’t worry” strategy, but most days I charge to 80-100%, and get home with under 10%. My goal is to avoid supercharging and given my territory I usually can do it, but with very little range to spare.

I’d like to preserve my battery as long as possible because I’m already close to the limits of its range.

Is there a better strategy? Or do these various strategies make little significant difference?

P.s. Thanks for the Video it was great.

 

[Zoomit]

So, do you think my strategy of charging to 50% as soon as I arrive home “while the battery is still warm” and then setting it to finish charging/preconditioning to 80, 90, or 100% by my daily departure time the next day, doesn’t really help lengthen my battery life?

// cut //

Is there a better strategy? Or do these various strategies make little significant difference?

It sounds like you're using the battery aggressively, with routine deep discharges, but have a reasonable charging scheme to minimize degradation given that usage. I don't know of a better strategy. The open question is how much do these tweaks to recharging strategies actually reduce degradation. I can't answer that. Remember high SOC loss is strongly correlated with high temperature, so the payoff of a split recharge session is less in Wisconsin than it would be in Arizona.

 

[rjpjnk]

I've owned the car for 8 weeks and have been averaging 1250 miles per week. My average will fall, but not by a lot. Long term I believe I'll average about 800 miles per week.

Since you have only owned the car 8 weeks you have yet to experience just how bad battery performance is in cold winter weather. I don't know Wisconsin to well, but I think it gets cold there. Is this right? Here in NJ I would say I lose at least 20% capacity in the winter. Also, takes longer to charge, and the regenerative braking doesn't work until the battery has warmed up for about 30 minutes at least. Batteries and cold really don't get along too well. Your two-stage charging technique may help with the regen issue since it will warm the battery before the trip begins.

 

[dafish]

Given your range needs you're a bit screwed. Aakee would tell you once past 55% SoC it's a bit moot, and certainly once you're at 80% the majority of the impact has occurred.

These thing said, charging back to minimum needed and delaying final charge to before you need it is a pretty solid plan. And about all you can do. Myself, I'd not schedule anything or use departure charge. I'd use Tessie automations to change my SoC level. I'd keep it at 53% as a norm and no schedule, and change it to whatever, lets say 75% charge pecent, at whatever time I know I needed to start to get that done by my departure time. That via a tessie automation. Then I'd set it back to 53% using a Tessie "on arrival" command.

If you find yourself SC'ing, as a I suspect you will this winter, I suppose I'd charge no more than i needed at my departure leg to make it to the SC. Then I'd charge no more than I needed to get back.

And yea, I too don't see any reason to not manage the battery for best degradation results. others don't care for it.

 

[gad1976]

Given your range needs you're a bit screwed. Aakee would tell you once past 55% SoC it's a bit moot, and certainly once you're at 80% the majority of the impact has occurred.

These thing said, charging back to minimum needed and delaying final charge to before you need it is a pretty solid plan. And about all you can do. Myself, I'd not schedule anything or use departure charge. I'd use Tessie automations to change my SoC level. I'd keep it at 53% as a norm and no schedule, and change it to whatever, lets say 75% charge pecent, at whatever time I know I needed to start to get that done by my departure time. That via a tessie automation. Then I'd set it back to 53% using a Tessie "on arrival" command.

If you find yourself SC'ing, as a I suspect you will this winter, I suppose I'd charge no more than i needed at my departure leg to make it to the SC. Then I'd charge no more than I needed to get back.

And yea, I too don't see any reason to not manage the battery for best degradation results. others don't care for it.

Thanks! I'm curious about the number 53. Any particular reason you charge to 53%? I like odd numbers, so I might switch to that, but curious the reasoning you use it.

 

[gad1976]

It's possible your BMS has a poor calibration on the full battery capacity due to your anxiety about not leaving it at high SOC. To help the BMS calibration, do a full charge from a resting very low SOC to 100% and let it rest (2 hours sleeping). Cycling this a few times may be required. Each cycle may degrade the battery by ~0.05% [source, reference thread]--It will be ok, you and your car will survive!


Yes, and...

View attachment 966370
From:

Oh, I was also gonna ask if it was important to calibrate the BMS. Does the calibration do anything functionally useful or is it simply for a numbers nerd (like me) to get more accurate data? Thanks.

 

[dafish]

Thanks! I'm curious about the number 53. Any particular reason you charge to 53%? I like odd numbers, so I might switch to that, but curious the reasoning you use it.

Well spotted. Forum member AAKEE, who has done more research on this than most (look for his posts, they are very informative), shows us that degradation takes a considerable jump at 55% as displayed (corrected for pack reserve). I don't need more, but we're also unable to charge to much less. I ALSO don't charge all the way up (ever), or all the way down. Member WK057, who is literally in the Tesla EV battery business, tells us the BMS is exceptionally accurate and really doesn't need full range excursions to be so. My experience echos that. Granted I'm not pack balancing, but then I'm not looking for that last erg of range. I simply pulled a few percent below 55% as insurance to BMS error and selected 53%. You could pick any number between 50 and 55% and feel like you were doing the best possible.

None of that is to say pack balancing isn't a good idea. At this moment I don't believe is adds anything to battery longevity. I believe it to only be of value in ultimate range (I may be wrong). One day I may look more into exactly how to accomplish same and let it charge to 98% or something. I certainly don't expect a few times a year to cause enough impact to matter, and I'd drive it reasonable soon after. I believe balance does take some hours, but I'd need to study to be certain.

YMMV, but if I was going to accept advice from forum members on these topics the two gentlemen mention above are as well versed as you're likely to find outside of a lab. Hopefully I've replayed their coachings to this forum reasonably well. If not faults mine.

ATB,
-d

 

[Vinnigan]

I was talking to my neighbor with a Y. He's a mechanical engineer and fairly passionate about cars. I asked him about his degradation and he's only lost about 3% after 30k miles. I asked him how he managed to achieve such levels since those numbers seem to be extraordinary and his answer was to avoid supercharging.

This seems to match up with OP's graph since the largest drop occurred after the road trip.

I've only been so far under the impression that staying at high SOC is to be avoided, but did not realize that supercharging could accelerate degradation. Can anyone shed more light on the effects of supercharging?

 

[fhteagle]

Jeff Dahn is probably in the top 0.001% of battery experts in the world. His advice is gold.

 

[RedY23]

I was talking to my neighbor with a Y. He's a mechanical engineer and fairly passionate about cars. I asked him about his degradation and he's only lost about 3% after 30k miles. I asked him how he managed to achieve such levels since those numbers seem to be extraordinary and his answer was to avoid supercharging.

This seems to match up with OP's graph since the largest drop occurred after the road trip.

I've only been so far under the impression that staying at high SOC is to be avoided, but did not realize that supercharging could accelerate degradation. Can anyone shed more light on the effects of supercharging?

Not sure to what extent he is right based on observations of his own car. I lost 8% since Febuary and used the supercharger only 2 times for 10min each time in 13000 miles. I charge to 90 every night, now 80% at teslas new request, and drive avg speed and acceleration. Now 285/306 miles at 100%. Gonna run the tesla batery service test and see if that yields more info.

 

[TigerNinety]

Hey,

We have different cars and different situations, etc. But... wow... that seems to be a lot of precision charging to go through. I could be totally wrong, but it feels like BMS can account for a lot of the issue you're worried about.

I normally charge my 2022 M3LR to 80%, 90% in winter here in the mid-Atlantic. The car has about 16K miles and now has a full-charge range of 344 miles (at least at the moment). That's above the new EPA-rated 333 mi, but a bit less than (I think) the original Tesla-rated 358. There's so much variance in all this, it's hardly worth worrying about.

I can't say you shouldn't worry, but... maybe worry less?

Good luck!

 

[johnny_cakes]

I asked him how he managed to achieve such levels since those numbers seem to be extraordinary and his answer was to avoid supercharging.

Latest research from Recurrent would refute your friend's hypothesis: Tesla battery longevity not affected by frequent Supercharging, study says

 

[johnny_cakes]

I simply pulled a few percent below 55% as insurance to BMS error and selected 53%.

The central graphite peak moves up with calendar aging (i.e. calendar aging degrades the top part of the battery capacity), so you have more insurance than you think. Source: What's better...full cycle charge or supercharging

 

[johnny_cakes]

Is there a better strategy? Or do these various strategies make little significant difference?

Your strategy is sound and based on research reports posted on these forums by @AAKEE, it should make a difference. You can simplify your life by letting it charge from arrival SoC to target SoC all at once and as late as possible instead of doing the 2 step approach, but if you need to have 50% SoC as soon as possible upon your arrival, I think your strategy is really good.

 

[AAKEE]

The central graphite peak moves up with calendar aging (i.e. calendar aging degrades the top part of the battery capacity), so you have more insurance than you think. Source: What's better...full cycle charge or supercharging

And moves down with fast charging, so maybe not to much headroom.

I guess regular cyles also might but I do not remember that part.

 

[RedY23]

Hey,

We have different cars and different situations, etc. But... wow... that seems to be a lot of precision charging to go through. I could be totally wrong, but it feels like BMS can account for a lot of the issue you're worried about.

I normally charge my 2022 M3LR to 80%, 90% in winter here in the mid-Atlantic. The car has about 16K miles and now has a full-charge range of 344 miles (at least at the moment). That's above the new EPA-rated 333 mi, but a bit less than (I think) the original Tesla-rated 358. There's so much variance in all this, it's hardly worth worrying about.

I can't say you shouldn't worry, but... maybe worry less?

Good luck!

Agree!!!!

I have been conservative since buying the car in February and its gotten me nowhere. A full charge yields 286 miles on a 2023MYP. New was 306. So I lost about 20 miles in range in under a year (13000 miles) despite not using supercharger despite mostly charging to 80 and driving in chill mode. I think each battery pack has its own personality