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Tesla Model S battery degradation data

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Re: Tesla Model S battery degradation data

#221

Post by friendzis »

There is one thing about batteries: Watt-hours battery will provide highly depend on current (electric current) draw. To some extent this also applies to deterioration. Which means that as batteries get more and more used, one should expect to see higher and higher disparity between range in sporty and economic driving. In other words as battery gets older, the higher consumption driving aggressively.

Tesla, however, has one redeeming factor. While battery voltage-capacity@current curve will change over time, Tesla can collect real world usage data and with software updates push updated curves for older batteries to adjust range estimation models for battery wear.

Re: Tesla Model S battery degradation data

#222

Post by kogepathic »

roman_savchuk wrote: post #204
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…

When I was reverse engineering car ECUs, one of the interesting little projects was finding fuel consumption display calibration data and calculation algorithm, on 2008+ Subarus. And then I did some measurements trying to get accurate real world consumption, and "sync" the dashboard with it. And while there was ~3% error IIRC, I think it has more to do with getting the most accurate average consumption over the car's…

> ECU can't count actual fuel 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?

Re: Tesla Model S battery degradation data

#223

Post by Slartie »

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…

I currently drive a 2015 Opel Astra. It shows an average of 5.1 liters per 100 kilometers (sorry, German, so it's metric units for me) over multiple months of driving in the dashboard. At the same time, I'm tracking every one of my gas refills using an app which also calculates consumption averages over arbitrary timespans. By that data, I am actually consuming about 6 liters per 100km, which is an almost 20% deviation. I thus stopped to trust the fuel consumption measurements of this particular car.

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.

Re: Tesla Model S battery degradation data

#224

Post by wiredfool »

dx034 wrote: post #188
myrandomcomment wrote: post #181

Earlier quoted context omitted.

It can be more confusing. US date - m/d/y. Distance in miles. If you are in the US military - d/m/y and klicks (km). Was in UK a few weeks ago and rented a car, mph for speed, everything else (except beer) in metric.

The UK is more complicated than that. Most of the signs are in metric but some distances are in yards and heights are in feet. Petrol prices are in litres but consumption is in mpg, even though there's no indication on how many gallons you actually fill up. In stores, everything has to be metric because of EU regulation but packaging for liquids is often in pints (e.g. milk, beer) and then gets translated into litres…

And stone for weight of people.

Re: Tesla Model S battery degradation data

#225

Post by Tepix »

72deluxe wrote: post #216
dcustodio wrote: post #205

Earlier quoted context omitted.

I fill up every time I refuel and I take notes of the quantity and odometer and the average matches the dashboard.

What manufacturer and model is that? 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.

How do you measure the distance driven? Perhaps the tachometer is also lying?

Re: Tesla Model S battery degradation data

#226

Post by roman_savchuk »

kogepathic wrote: post #222
roman_savchuk wrote: post #204

Earlier quoted context omitted.

When I was reverse engineering car ECUs, one of the interesting little projects was finding fuel consumption display calibration data and calculation algorithm, on 2008+ Subarus. And then I did some measurements trying to get accurate real world consumption, and "sync" the dashboard with it. And while there was ~3% error IIRC, I think it has more to do with getting the most accurate average consumption over the car's…

> ECU can't count actual fuel 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?

Never saw a separate fuel flow sensor in an automotive application, but fuel injector is technically an orifice flow meter in this calculation method (pressure differential is constant and you calculate how much fuel is flown through orifice by measuring time it is open). Sure, when orifice size is reduced by lacquer depositions or dirt it will cause measurement error. But it will also cause increasing fuel trims (to the point when CEL goes on) and bad driving performance when fuel trims don't apply

Re: Tesla Model S battery degradation data

#227

Post by Unklejoe »

kogepathic wrote: post #222
roman_savchuk wrote: post #204

Earlier quoted context omitted.

When I was reverse engineering car ECUs, one of the interesting little projects was finding fuel consumption display calibration data and calculation algorithm, on 2008+ Subarus. And then I did some measurements trying to get accurate real world consumption, and "sync" the dashboard with it. And while there was ~3% error IIRC, I think it has more to do with getting the most accurate average consumption over the car's…

> ECU can't count actual fuel 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?

> 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.

Re: Tesla Model S battery degradation data

#228

Post by tyingq »

dom0 wrote: post #211
seszett wrote: post #53

Earlier quoted context omitted.

I don't know, but if the average is 220 000 km (according to the article) I'd say a fair share of cars must go beyond that. 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…

Gasoline engines can be plenty reliable. I think the main reason why a lot of cars from the 80s and 90s are able to go to 400k and more is (1) cheaper and easier maintenance, so more inclined to do it regularly (2) no fancy shit going on, no turbo chargers, no high-pressure fuel injection, thus far less wear on parts, no unreliable high-pressure pumps etc. Replacement parts on these are also far more expensive. New t…

Aluminum heads are part of why some newer cars don't last as long. It's easier to blow a head gasket. Replacing those in a tightly packed front wheel drive engine bay often exceeds the value of the car. Or, driving with the blown gasket causes overheating that damages other components.

Re: Tesla Model S battery degradation data

#229

Post by freehunter »

Tepix wrote: post #225
72deluxe wrote: post #216

Earlier quoted context omitted.

What manufacturer and model is that? 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.

How do you measure the distance driven? Perhaps the tachometer is also lying?

Very good point. Odometers (tachometer measures RPM, odometer measures distance) are not as reliable as some may believe, and even if they're perfectly accurate, there are so many variables that it's hard to control. Smaller tires spin faster, which drives up the miles read. Tires get smaller as they wear, so the odometer can be calibrated for new tires but will quickly become inaccurate.

But the odds that your odometer is accurate is very slim in reality: http://www.azfamily.com/story/19769079/tests-show-odometers-...

Re: Tesla Model S battery degradation data

#230

Post by Roritharr »

aphextron wrote: post #165
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.

The real killer for laptop batteries is the fact that they are kept at 100% charge plugged in while under extreme thermal stress. Temperature + full charge kills li-ion batteries. Do your laptop a favor and never charge to 100% unless you really need to.

My Toshiba has the option of only charging it to 80% while plugged in, called Cell-Saver. Just feels better not having to worry about cell degradation.

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.

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