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Tesla Model S battery degradation data

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Re: Tesla Model S battery degradation data

#241

Post by WorldMaker »

wongarsu wrote: post #101
kbenson wrote: post #8

> The red fitted line has a slope above 60.000 km (say 40,000 miles) of 1% per 50.000 km (30,000 miles). I'm going to bring this up because I think it's both interesting, and sometimes it comes up on its own and detracts from the conversation with conjecture (and sometimes harsh assumptions) until covered adequately[1] - different countries have different conventions for whether they use a comma or period for a thous…

>but there's not really any standardization of this as far as I know There is. Resolution 10 of the 22nd General Conference on Weight and Measures [1] (the body responsible for the SI system) forbids the use of comma ordot as thousands separator. Other institutions like NIST have followed suit, forbidding or at least recommending against it. The recommended approach is to use spaces as thousand separators (or ideally…

Interesting reading. Resolution 10 only declares the decimal separator, leaving that to language convention still whether to use comma or dot (as opposed to finally unifying that, wouldn't that have been something?). As for thousands separators, it just reaffirms Resolution 7 of the 9th CGPM from 1948 which made the declaration of spaces, never dots nor commas.

So it's actually been since 1948 that the GCWM/SI system has been recommending spaces as grouping separator? Wow.

Re: Tesla Model S battery degradation data

#242

Post by dsfyu404ed »

dalbasal wrote: post #200
toomuchtodo wrote: post #153

Earlier quoted context omitted.

Musk has made a comment on an investor call that they're targeting a million mile lifespan for the motor.

I think ICE cars are just not optimized for prolonged life. Many countries have policies discouraging long lifespans, more than ever since emmissions laws. Also, EOL for a car is several owners and 5-10 years removed from first purchase. This adds up to a realtiy where doubling the expected lifespan is not worth much more, in sales. Basically, if Tesla want to make this a goal then beating benchmarks should be relati…

x2. Modern vehicles have a targeted minimum lifetime based on certain usage models. That's why people who are driving a pickup truck around all day for work with a few hundred pounds of equipment (e.g. medical equipment service technician) get 500k+ out of them and oil field trucks are beat before 100k.

Re: Tesla Model S battery degradation data

#243

Post by jakobegger »

Meegul wrote: post #148
leggomylibro wrote: post #32

Earlier quoted context omitted.

I wonder if they're particularly good at balancing the cells. When people recycle 18650s from laptops, I think it's often because one or two cells went bad while the rest remain fairly healthy. Similarly, if you put things like batteries or capacitors in series, you typically want circuitry to balance their voltages, because a pair of 2.7V elements charged to 5.3V could really be at say, 2.75V and 2.55V, which would…

A Tesla focused Youtuber recently did a video [1] where he accessed some of the data on the CAN bus, and it showed excellent balancing between the cells. The highest voltage cell reported 3.87V, with the lowest voltage cell reporting 3.864V. So the highest voltage cell has only a 0.1% higher voltage than the lowest. That's in the middle of a discharge cycle, so this may not be representative of the real capacity diff…

Presumably they have a lot of cells in parallel? This would help with balancing, since individual cell differences would average out over all the cells that are parallel.

Re: Tesla Model S battery degradation data

#244

Post by jandrese »

photojosh wrote: post #124
digikata wrote: post #119

Earlier quoted context omitted.

A lot of these could be mitigated if phone makers were willing to put in a slightly larger capacity battery and apply more conservative max-min limits in their battery management system. But I guess companies are happy to keep sales up via planned obsolescence.

My phone rarely gets below 50%, and I'd say it only gets below 20% a handful of days a year. But yes, I've often thought it would be nice to have a toggle to say "Prolong battery life (as in years)... I only want a 90% charge since I'm not going to be using much tomorrow." I've wondered too whether I should only use a slow (1A) charger for the overnight charge rather than the full 2.4A. But then again, I only keep my…

I have a Lenovo laptop with this feature. It only charges the battery up to about 60%, which is fine since that laptop is plugged in a lot. When I am planning to take it out I'll turn off battery safer mode and let it fully charge.

Re: Tesla Model S battery degradation data

#245

Post by jandrese »

WillPostForFood wrote: post #82
dmitrygr wrote: post #9

This is fundamentally flawed because lithium batteries mostly degrade not because of amount of use, but because of time (and their charge state and temperature during this time). No matter if used or not, they will lose capacity. The rate of capacity loss is mainly dependent of average charge (best is 40%, worst is 100%) and temperature (best is 5 degrees C, the higher the worse). (This is also why phone batteries fa…

So if you were optimizing your phone for low battery degradation, when would you charge it, and to what %? If you were trying to keep it around 40%, would a good strategy be to let drop to 20%, and then only charge to 60%, or would you bias it even lower to keep it away from 100%, like a working range of 10-50%?

Maybe schedule it like so:

Between 6AM and 8AM: Charge to 100% All other times: Charge to 75%

So the battery is topped off in the morning right before you put it in your pocket for the day, but otherwise doesn't fully charge to save the cell life.

Re: Tesla Model S battery degradation data

#246

Post by jandrese »

TomMarius wrote: post #196
justinph wrote: post #142

Earlier quoted context omitted.

> Average life of ICE vehicles can't be 266kkm, that's absurdly low. People buy a lot of Chryslers, Fiats, Fords, and Chevys. You'd be lucky (or cursed, depending on how much you hate the car) to make it to 266kkm with a Chrysler Sebring, for instance.

That's interesting because I know a lot of people with European Fords (Mondeo, Focus), myself and my family included, that went well over 350k km. Are the American Fords so incredibly bad?

I think it's more that people who never maintain their vehicles don't expect them to last past 100k miles. If you follow the manufacturers suggested maintenance regime in the manual it will last much longer.

Unfortunately, this means the used car market is also full of moderate mileage vehicles that require a ton of preventative maintenance as soon as you buy them, giving the used cars a bad name.

If you buy a used Chrysler with 100k miles, its probably 40k miles overdue for a timing belt replacement, transmission filter change, radiator flush, alignment, brakes, tires, etc... On the plus side, you probably got it pretty cheap.

For one point of reference, Ford was notorious for "value engineering" the old US Rangers so they would die around 150k miles, but I kept mine running for 250k miles and 23 years with mostly just regular maintenance and the occasional repair. The thing that finally killed it was an aftermarket slave cylinder for the clutch that failed and blasted brake fluid all over the inside of the transmission.

Re: Tesla Model S battery degradation data

#247

Post by tjoff »

linsomniac wrote: post #231
jakobegger wrote: post #182

Doesn‘t anybody find it curious that the source of data are range estimates displayed on the cars built-in dashboard? For all we know, Teslas might be programmed to show more „optimistic“ estimates as the batteries get older. I‘m not saying this is actually the case, but these stats are effectively manufacturer-provided numbers. Would you trust data like this if it came from any other car manufacturer? If you have a…

The Tesla is strange because that number on the dash is "rated miles", or the best you're going to get. So you can't just drive to empty and get a number you can compare with others, unless you drive it in quite a certain way. My S60 says something like 215 miles when fully charged, but when driving on the Interstate the actual range is more like 160 miles, with the cabin heater on. It can vary significantly due to r…

Can't you measure how much energy is used during charging?

Re: Tesla Model S battery degradation data

#248

Post by evandijk70 »

hwillis wrote: post #114
GuB-42 wrote: post #102

That's quite impressive. What I am wondering is why they do do well, barely losing 10% in 5 years, compared to phone or laptop batteries that last maybe 3 years on average. AFAIK, they use the same technology, in fact, I wouldn't be surprised if the same batch of cells end up partly in Teslas and partly in laptops.

In order of importance: 1: Tesla cells are hard limited to a lower voltage, reportedly 4.1 V rather than the 4.2-4.4 V maximum. Phone batteries run much closer to their maximum voltage 2: Tesla cells stay at much lower temperatures and have active cooling. Phone batteries are used to sink heat from the processors and wifi. 3: Teslas have a much lower normal depth of discharge. In addition to the derated voltage, the…

I think this is a good list, but I think reason 3. should be higher up. Rule 3. worded differently:

3. Rule of thumb is that a battery lasts around ~1000 cycles. Phone batteries are discharged fully about once a day, so that leaves a lifetime of almost 3 years.

Tesla range is ~ 300 miles, so using this rule of thumb it should last around 300,000 miles. This + reasons 1,2,4 and 5 are why the battery barely degrades over the lifetime of the car.

Re: Tesla Model S battery degradation data

#249

Post by hwillis »

moepstar wrote: post #178
hwillis wrote: post #75

Earlier quoted context omitted.

>Average life of ICE vehicles can't be 266kkm, that's absurdly low. It appears to be the consumer reports data. [1]: http://www.nbcnews.com/id/12040753/ns/business-consumer_news...

Add one or two zeroes at the end and i'd guess we'll be more in the ballpark..

what...? You're saying cars can drive 1.5 to 15 million miles on average? They barely ever make a million miles[1].

[1]: https://www.autotrader.com/car-news/ive-been-using-a-950000-...

Re: Tesla Model S battery degradation data

#250

Post by taheca »

linsomniac wrote: post #231
jakobegger wrote: post #182

Doesn‘t anybody find it curious that the source of data are range estimates displayed on the cars built-in dashboard? For all we know, Teslas might be programmed to show more „optimistic“ estimates as the batteries get older. I‘m not saying this is actually the case, but these stats are effectively manufacturer-provided numbers. Would you trust data like this if it came from any other car manufacturer? If you have a…

The Tesla is strange because that number on the dash is "rated miles", or the best you're going to get. So you can't just drive to empty and get a number you can compare with others, unless you drive it in quite a certain way. My S60 says something like 215 miles when fully charged, but when driving on the Interstate the actual range is more like 160 miles, with the cabin heater on. It can vary significantly due to r…

were you driving it manually, or using Autodrive? Were you driving it conservatively, or heavy on the accelerator?

Did you stay at a consistent 55 - 60mph, or were you going faster?

There are a lot of factors in play for a electric vehicle.

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