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 gasoline car, do you trust the fuel consumption rate displayed on the dashboard? Should journalists trust it? Or should they measure how much gas they put in the tank and divide it by distance driven?
Thanks, this is pretty interesting.
It's the first non-bullshit explanation I've seen for why cars tend to display inaccurate average MPG on the dash. I always assumed there was a fully accurate measure of fuel flow into the engine and there was something else broken (or dishonest) about that calculation.
This has come up in the press occasionally and the manufacturers never admit that they don't have a totally accurate measure of flow:
That doesn't seem right. Flow sensors exist and could be fitted to the fuel line to the engine for a precise measurement of how much fuel is consumed.
So I'm assuming manufacturers just estimate fuel flow in the ECU because a flow sensor would be additional cost for negligible benefit?
Exactly. It's basically unnecessary given the other sources of information that the ECU has at its disposal.
It knows the target fuel pressure (some cars even have fuel pressure sensors) and it knows the flow characteristics of the injectors with respect to pressure and pulse width. That alone is enough for a decent calculation of fuel mass flow.
In addition to this, the ECU is also calculating the mass air flow into the engine, either directly via a MAF sensor or indirectly via manifold pressure, VE, and RPM (known speed density).
When it goes to target a specific air/fuel ratio, this is all the information that is really required. However, since injectors tend to deteriorate (clog, stick, etc.) over time, this initial calculation is usually “trimmed” by means of feedback from the oxygen sensor(s).
At the end of the day, there’s a fair amount of information available to the ECU which can be used to refine the fuel flow calculation.
The fuel consumption calculation on my 335i is usually within 0.5 MPG. However, my 2002 Maxima was about 3 MPG off.
Before that, I had an old and small 2005 Peugeot 206. The measurements of that car were like exact matches (at least to the first decimal digit) with my manual consumption tracking.
What really baffles me is that the newer and more expensive car is the one with the huge deviation, not the older and cheaper one, as you might expect.
My car tends to value the long range drives on a highway way higher then my average driving habit while commuting. So the higher consumption outliers on the highway tend to skew my results.
I had a 2008 VW Golf TDI Gt Sport (the 140PS PD engine) and that consistently lied. My newer 150 Euro6 (I think) engined VW Beetle TDO gives even better MPG so perhaps it is lying again...
Potentially time to measure it versus how much I put in.
But the odds that your odometer is accurate is very slim in reality: http://www.azfamily.com/story/19769079/tests-show-odometers-...
In the 60.000km's I've driven that car, I NEVER were able to get even close to 40km on a charge.
I think it is not necessarily due to the car but because of the calculation methods they use. If you drive motorway and city, consumption is accurate. But as soon as you start driving in the mountains or a mix of different terrains, data often vastly differs.
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 rain as well, a recent trip that had a leg almost entirely in very heavy rain caused a significant drop in range.
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.
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 - different countries have different conventions for whether they use a comma or period for a thousands separator, and in those languages if they also speak in English sometimes, they may choose to continue using a period as a thousands separator as is convention in their country, even if the predominant language in their country is not English, and there are circumstances which might make that more common for some people.
In this case, we have what appears to be switching convention when switching unit systems, which is interesting. I'm not sure if it's more or less confusing in the end, but there's not really any standardization of this as far as I know, so it's all good.
There is. Resolution 10 of the 22nd General Conference
on Weight and Measures  (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: thin, non-breaking spaces).
You are still seeing a lot of people do it wrong because the resolution is from 2003, and these things take decades to overcome entrenched preferences.
So it's actually been since 1948 that the GCWM/SI system has been recommending spaces as grouping separator? Wow.
I'm inoculated against confusion about this because I've done a lot of software and content localization, and have a grasp on the specifics for a lot of different cultures.
I think the problem is exacerbated by the underuse of the SI system's prefixes. Why even talk about thousands of kilometres when you can speak in tens of megametres?
I figure it's getting to the point where there are too many genuine English locales to keep up. It takes a lot of energy for normal people to retain fluency in dialects and locales like en_US, en_IN, en_CA (thankfully rapidly merging with en_US), en_GB, en_AU, en_JM, en_MY, etc. etc. etc.. all at the same time. Maybe at some point there will be a great and natural convergence.
It's funny how in Canada we have some specific remnants of the imperial system. Most people under 50 have no idea what a Fahrenheit is (myself included), except for pool water and oven temperature. Go figure.
People complain about inconsistency and lack of standards in the use of measurements in the U.S, but it is actually much more consistent there. It turns out that decimal units aren't really better for any practical purpose in a typical person's life, and it's certainly worse if you need to know both!
Even in the U.S. of course, engineers, mechanics, plumbers and others still have to deal with a mix. Think metric-based and imperial-based bolts, metric v. imperial lumber sizing.
s/U.S./the entire world/
It's very common to have international U.S. based companies offer N types of fasteners/whatever in imperial sizes, but only N/2 in metric. So we frequently build stuff in imperial sizes because of greater flexibility.
And don't get me started on (non)tapered pipe threads... I've heard some horror stories of huge subassemblies built in Europe using BSPT and shipped to the U.S. for final assembly, where of course everything else is NPT, so some poor sod has to spend a month replacing all subassembly fittings.
Probably because when you're speaking about them colloquially, you don't say "kilometres" you say "kays". That probably varies by locale too, I'm in en_AU. How is it over your way?
I do like the nerdiness in the idea of saying "two megs" instead of "two thousand kays", but it's never going to happen.
It's mixed here in en_CA (I've lived in Calgary, Vancouver, and Toronto at different points). In my experience, kay is used for kilometres when talking about manual travel/exercise (bicycle, running) as in "couch to 5k", but it's almost always klicks or kilometres when talking about driving, and usually only kilometres when talking about most other forms of transport.
Temperatures are usually in Celsius but are shown in F once it gets hot (100 degrees sounds better than 38).
Even though I'm a fan of the metric system, being in the US is easier than the UK, at least measurements are consistent...
There are other oddities and mixed units. Dates are in "drunk endian" with month/day/year format, indoor areas are measured in square feet and outdoor areas in acres... Small units of length are in fractions of an inch unless you're a machinist at which point they're in "thous" or "mills" (same thing, 1/1000 inch) or "tenths" (1/10000 inch). Drill sizes are fractions of an inch for some common sizes and large diameters (27/64 and up are always fractional), but otherwise are numbered starting at 80 and decreasing down to 1 as diameter increases with the spacing between numbers being inconsistent, except for a series starting at 2340 thou and ending at 4130 thou which is lettered with 40 thou between letters (mostly, some inconsistencies here). But you can still get drills in some of the fractional inch sizes that fall between the letters. Seriously, look at a tap drill chart. And of course if you're a machinist you'll also have to deal with metric items imported from the rest of the world or made for sale there so you'll also need all the metric drill and tap sizes.
Electric systems use SI units, except that PCB designers tend to use thou for trace sizes and spacing. Some components have pin spacing in thou, others in mm. Getting the PCB to look nice with a mix of pin pitches and grid sizes is more of a chore than it should be.
"K" is short form thousands as well written and pronunciated "k".
20,000 = 20k.
But when talking about distance specifying units, you say the thousands and "k" as in short form kilometers.
20,000km is pronounced: "twenty thousand k" or kilometers.
But if not specifying the unit, you could say I drove twenty "k", as in "I drove 20 thousand (kilometers)"
But they are not the same!!oneoneone. Unless you are in the dog food prefixes camp. Are you?
You're not thinking of the mebi-, kibi-, etc debacle, are you?
Ah... screw it: https://www.xkcd.com/394/
English as first language, but 2nd/3rd language for immigrant parents.
I have very rarely seen space separator for thousand seperate, maybe one some bank drafts.
Everyone I know, and I have used the comma seperate.
Officially may be a Canadian thing, but not used really
It's better to use no punctuation at all if you want to internationalize.
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 average American's daily driving distance is ~30 miles or 10-15% of the battery capacity. Phones are often almost totally discharged every day. Tesla's are also typically only charged to 80%, although you can turn that off.
4: Teslas have a low average power use: 300-600 horsepower on tap but cruising on the highway uses very little. In technical terms their current rate is ~.2-.3 C, while phones can have much higher C rates.
5: Phones use an LCO chemistry, Teslas use NCA which is more stable over the long term. Tesla also has custom additive and cathode/anode materials that improve lifespan a great deal.
Phone and laptop batteries almost all come from china, Tesla batteries are korean. They're pretty premium as far as 18650s go so they're used in power tools and really good laptops. However Tesla has their own proprietary chemistry so nobody else gets to use their blend.
There are also some (rather weak) reports that if you take the individual 18650 cells out of a tesla battery they last significantly longer than the NCA 18650s you can actually buy from Panasonic, which indicates that they might made to better manufacturing tolerances or something, but it's really all about Tesla's treating the batteries much better during use.
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.
I'm glad phone manufacturers heavily optimize for the first 2 and not the latter.
You can spin this in a bad way ("planned obsolescence") or a good way (they were optimising for other things that customers valued), but the point remains the same, if car manufacturers (or grid storage units) require longer lifetimes, then it's not a hard physical limit at the current lifetimes that's been hit yet.
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 phone for 2 years before passing on it, so I've not had to care that much.
I mentioned this to a colleague lately who looked at me like a strange animal for having:"worry about cell degradation" even on my list.
No, it's not. NiMH have practically no degradation from cycling, which is why Toyota still uses them in the Prius. The tradeoff is in energy density.
Li-Ion batteries are not meant to be held at 100% State of Charge (SoC). There is a non-linear relationship between average SoC over the life of the cell and the rate of degradation. Optimal charge for extended life in a typical 4.2v cell is around 3.9v, or 65% of available stored energy. Keeping an average SoC near 100% can cause up to a 5x loss in battery lifetime. See the link below . Specifically "Table 4: Discharge cycles and capacity as a function of charge voltage limit."
Would be cool if there was a similar feature available on phones. Maybe you could rig up something with Tasker or the like on an Android.
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 relatively easy.
(This is also why phone batteries fare so badly: they are often near 100% charge at 36.6 C in your pocket)
Figure 3 from the paper, "Cause and effect of degradation mechanisms and associated degradation modes," shows time as just one of 8 degradation mechanisms affecting lithium ion batteries. Other figures/tables from the paper do not emphasize time as the primary degradation mechanism, nor does the body text. Nor is there any explicit passage-of-time term in the final diagnostic model that the authors develop.
It's the same reason that you see early Leaf cells die out in Arizona while Tesla's have held up to 100k+. Thermal management makes or breaks longevity.
> not because of amount of use, but because of time
Which makes it seem like time is more important that heat.
think of it more as
BADNESS = integral(abs(temp - 5), over time) * integral(abs(charge_amt - 40%), over time)
use = (discharge + charge)
hence: heat = use ;)
You did mention 100% and temperature being the problem generally though...
For the remaining 8 hours, while I'm sleeping, it's at close to 100%; which is not ideal. I'd be curious how effective an overnight charging scheme would be that charges up to 40%, then holds it there until say 4 a.m. (or some other time based on the phone consumption, capacity and charger output) then charges up to 100% so that when you wake up it's fully charged.
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.
Though these tests are evidence of that, it's definitely not a common belief.
Before the Tesla data, what informed you?
One point (100 °F ~ 37 °C) doesn't make a scale.
0 to 100 on the Fahrenheit scale is "Really Cold" to "Really Hot".
0 to 100 on the Celsius scale is "Kinda Cold" to "Unsurvivable Hot".
When I say it's "human-centric" I mean that it maps well to the range of human comfort (Celsius is obviously vastly superior in just about every other use).
Maybe it's unsustainable, you can't survive that indefinitely. But you can't survive 0° F indefinitely either, unless we bring protective clothing into the game.
Edit: 100C is boiling point for water - is the ambient temp of the Sauna 100C?
Finnish saunas are kept very dry. Sufficiently dry air makes very hot temperatures bearable because evaporation cooling from sweat gets more effective the dryer the surrounding air is. Water on the other hand makes sweating useless, which is why you can't tolerate water temperatures above body temperature (depending on how much of you is submerged).
Apparently so! TIL.
I'm in the UK we switched to C for temperatures back when I was a kid (I still vaguely remember both been used on weather charts back when they stuck the things on by hand..), 0 is cold, 10C is brisk, 16C is perfect, 20C is warm, 30C is hot, 35C is "kill me now".
In any case thanks for the source!
Li-Ion battery degradation is generally modeled as two (roughly additive) components, called calendar and cycle aging. Calendar aging is what you're talking about in your comment - it's basically determined by the temperature and state of charge. Both of these impact the rate of chemical processes that lead to loss of lithium and active material. This is what happens when the battery is sitting on the shelf.
Cycle aging, on the other hand, happens when you charge or discharge the battery and is driven mostly by the actual volume change in the anode and cathode when they get lithiated (it's quite significant, up to 15% or so in some materials). This introduces mechanical stress, which can break the protective film that forms between the electrodes and electrolyte and allow chemical degradation to proceed at a faster rate. The degree of mechanical stress is mostly determined by the depth of discharge, although rate of charge and discharge is also believed to be important. Cycle degradation is also impacted by the temperature at which the battery is cycled, in a similar way to calendar aging.
With high temperature variance (low temperatures will wreck your batteries too, and I can't recommend keeping them at 5C), calendar aging is the dominant mode. This is absolutely the case with cell phone batteries. However, electric vehicles, especially higher end ones like the Tesla, have an active cooling system that keeps the battery at a constant temperature, even when the car is "off". This is why many EVB warranties will be voided if you let them run out of charge for more than 14 days - at that point, the cooling system isn't working and your poor battery is at the mercy of the elements.
Under closely controlled temperatures, cycle aging is the most important factor, and it's dominated by depth of discharge. If you drain the battery as far as it will allow you every day, it's going to be hosed. If you only go down to about 80% of the allowed charge every other day, it'll last for quite a while. These numbers are roughly correlated, obviously, with the mileage on the car, but the relationship is not simple, and I'd caution against considering mileage to be a good determinant of battery degradation.
Some good sources if you want to learn more:
A fairly simple model of degradation (ignores charge/discharge rate):
A thesis on the subject, goes into great detail and has an excellent bibliography:
The speaker (Jeff Dahn -- he now works with Tesla) pioneered a faster way to tell how fast a battery will degrade (which means you can iterate your design faster!)
My single datapoint at 60k is I've seen only 2% degradation which is phenomenal.
They use the same 18650 cells that power laptops, yet laptop batteries degrade badly over time. My 1 year old XPS13 reports a battery "wear level" of 29%.
I wonder if Tesla's battery technology could be used in laptops and phones?
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 be unhealthy for the former cell. I think those imbalances are also caused by small differences in the individual elements' properties (capacitors are typically less precisely-tuned than resistors) which will drift further over time with wear and temperature changes and overvoltage conditions and whatnot. So that 2.75V cell would degrade very rapidly compared to the 2.55V one, probably causing even larger imbalances until it eventually fails.
Most lithium cells have basic protection circuits built-in against over/under voltage and overcurrent (e.g. shorts,) because they tend to explode if you leave those things out, but they definitely last longer if you pay attention to them as individual cells rather than a system.
1 - https://youtu.be/F3tF0i98MpI
Sure, if you want a laptop which you can only recharge once per week.
Laptops and phones go through charge cycles much faster than cars; I'm sure Tesla has tuned their designs to maximize performance in that usage environment.
What is also an advantage: Teslas can cool (and I believe also heat) the batteries so they don't enter temperature ranges where degradation is accelerated. In a laptop and certainly a phone there is neither space nor weight available for a thermal management.
Laptop and phone batteries are physically close to heat sources + are used frequently to substantial degrees of discharge + frequency of charge cycles after substantial discharge.
I'm pretty sure cell phones do this too.
Ironically, more modern cars will probably not last as long! I can rebuild just about anything on this car, electronics included (most complicated part is perhaps a common opamp). On modern cars, as soon as the advanced ICs (say an ECU) are NLA you’re SOL.
It's only the few that were both made better, with no production flaws, and great maintenance that have lasted long enough for us to see then with 150k miles before being purchased today.
My car is at 350 000 km now, and I'm not planning on selling it anytime soon. It doesn't have any special problem, except for a malfunctioning electric window lifter on one side. It's only one data point of course.
There is some percentage of cars crashed in the first week. It only takes a few of these to cancel out the average of extreme outliers like your car.
For reference I have never seen an odometer with more than 200 000 on it before. Even most classic rebuilds I have seen like 69 Corvettes have some high 100K count on them, some event have reset odometers.
If I had not bought my car (it was at 300 000 km) I'm pretty sure it would have been sold in Eastern Europe instead, or maybe Africa since it's a Peugeot (a 406).
In the countryside, it's also very common to have both a nice recent car, and an old reliable one like mine for the dirty work. Most people I know do have one car that is a few 100 000s of km. Also, we mostly use diesel here, and these are supposed to be much more reliable than the gasoline engines used in the US (and I'm not going into the purported lack of reliability of American cars to begin with). I'm talking about everyday cars that are 15 or 20 years old, not classic cars.
Replacement parts on these are also far more expensive. New turbo is a four-figure number just for the part. Injection pumps are bloody expensive, too.
Less optimized designs may also be a factor. CAD and FEM modelling has only become better with time, so back in the day engineers would rather make a more conservative design, nowadays that's not so necessary any more.
Perhaps they don't build them like they used to, but our 1980's Honda sedan also easily clicked over 350,000kms too.
Turns out it has gone round the clock...
There's probably a Youtube video that'll walk you through how to replace it. I replaced the one on the driver's side door of our 2001 Honda Odyssey last year. I think it was like $120-150 (USD) for the part and 3ish hours. I know almost nothing about fixing cars (just generally how to use basic tools), but have used info from forums and (especially) youtube to fix several things like that on our cars.
[EDIT] great thing about the Youtube videos is you can get a good idea of whether it's something you can manage yourself before you tear your car apart.
I have a 2004 Corvette with about 140,000 miles. Stuff breaks, but it is a vette. My last F150 had about 160,000 miles when I, uh, wrecked it. Still looked and drove like new.
'99 Toyota 4Runner, 232K miles (currently own);
'85 Honda Civic, 197K miles;
'59 VW bus, ~490K miles (with a rebuild of the 40hp engine at ~240K miles and a transaxle from a junker at ~300K miles).
You are ridiculously hard on your capital equipment. It must be nice not to have a care in the world for your expensive possessions. Personally I couldn't bring myself to torture fine machinery like that.
I don't know why my friends parents had lower mileage cars, but I know what it was with my mom:
At this point most cars were automatic, and they crammed lots of parts of the transmission into a hard-to-service single-part-number item. Three times while I was growing up (~32 000 km per year driving) she had the transmission fail at around 170 000km and the mechanic quoted her a number approximately equal to the street-value of the car to fix.
It appears to be the consumer reports data.
Being german, i immediately associated ICE with the train of Deutsche Bahn which probably do around that mileage...
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.
Not everyone builds Corollas.
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.
And then there's the software... I don't have a lot of confidence in any company to supply software updates for multiple decades. I hope we don't end up in a scenario where wealthy people have secure vehicles and the less well-off just shrug and accept malware on their car as the price of living in modern times.
Also: Here we have a very strict road legality checkup (joints, breaks, rust, lights, belts, ..) for all cars. Once a bad/cheap car reaches the age when it starts failing the checkup, it's often not worth fixing. So while it could probably do another 100kkm with the dodgy wheel bearing, it's not allowed to without immediate expensive repair. So these checkups effectively purge every car that would need repairs to any vital parts costing more than its worth every year.
I have a 10 year old peugeot worth around $1-2k that has gone 18kkm. If it were to fail a checkup for even something simple like a wheel bearing or uneven handbrake appliance - I'd probably hesitate to repair it because I could just as well get another one (A recently checked one for $1k would limp along at least 1-2 years to the next checkup while mine is banned from the road immediately).
Car accidents are random in nature and significantly reduce average car's lifespan. Further, many cars age without being driven very far per year and 15+ year old cars are often junked even if they are relatively low mileage if they are part of even a fender bender.
You also have issues with rust independently from mileage.
I'm not sure it is...
I mean, in my country (Netherlands) the average car user drives 13k km per year, in very car heavy countries that's probably around 20k. But here it'd mean a car would last on average 20 years, that's not absurdly low by any standard.
Maybe someone could write a quick script to scrape AutoTrader.com or a similar site and see what the mileage is on cars over 20 years old that are offered. ;-)
It doesn't mean that car can't last longer than that, but more and more repairs are to be expected, and it is more likely to fail at any time. If you are a professional, keeping such a car doesn't make economical sense.
Furthermore, in high income countries, they actually want you to destroy these old cars to promote the new car market.
Also perceived safety/ convenience, a car might be good for another 100k km but appear unreliable enough that it might break down at any time.
Meanwhile, the 2006 Prius I bought two years ago just hit 110K miles (purchased with 80K miles), cost $10K, and has needed nothing more than new tires and a replacement cooling block on the engine (which was deferred by the previous owner). I plan on running this thing until they no longer can service it, a full swap of the hybrid transaxle is relatively cheap as is replacing the engine, but with regular maintenance they’ll probably last 500K or more and I’ll only have to replace the battery at some point.
Always do research on the reliability and cost of repairs on a car before you buy it, this alone was why I picked the Prius over other cars on the lot (there’s very little that can need serious repairs because of how simple the ICE design is, and the electric drivetrain components are pretty long lived as well).
 I've never got the hang of IPA, sorry