Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

[AAKEE]

They do do charge depletion for this test.

Yes, I know.

What I ment was that if you would drive a short drive with a cold battery, the loss would be huge (or if you would get all values after 30 min of the EPA test, as the losses are higher and the battery temp rise faster the colder the battery is).
After one-two hours the battery would be at ”normal” winter driving temps with lower losses.

Anyway the newer cars do better which accounts for part of the improvement in the magic scalar.

Yes, the heat loss actually can be used as cabin heat as soon as the cell temp is warm enough, so the energy still is used.
(The lost energy is only what needed to heat the battery to the ”heat pump-able”temperature) and at 20F the heat pump still can pump heat from the ambient air.

Check this bimmer, model year 2023
Charge depleting highway 86 kWh
Charge depleting 20F 58kWh !!!
(That, I do not get though…)
https://dis.epa.gov/otaqpub/display_file.jsp?docid=56032&flag=1

 

[AAKEE]

I still wonder about the reasons for the extracted energy differences at cold in EPA tests. I have a few theories but not sure which is right.

A little bit deeper about this, from memory reading a few years back:
The heat losses in the battery are of two kinds: chemical and electric. From memory they are about equal in size.

I actually did a calculation a few years back using data from EPA tests, out of curiosity.
About half of the 20F losses could easily be explained by the increased internal resistance, and as the research reports had the electrical losses at about 50%, i felt that I was ’home’ with that match. Its possible that some of this was refered to in some posts here when we where discussing the used energy vs change in nominal remaining.

If it is of interrest, it would be easy to do the calcs again, the loss in power is I^2 x R.

 

[AAKEE]

I made a 131 km drive today, started at -16C and just entered a snow storm when I arrived with around 0C.

Cell temp at start 24.5C and at the end 12.5C, so last part of the drive was with slightly colder batt than in the summer.

Nominal remaning delta = 28.6 kWh
Used energy according to the trip display 28.3 kWh. The delta should be the battery having larger losses than at standard temperatures.
A drive at higher speed (higher power) would also increase the loss and the delta, but this drive was not that fast, for a part 110 km/h (70mph) but also slower for some parts. The same driving speeds have shown no delta in both my M3P and the MSP.
Car outside during the night, so the battery would be around 0C when going home tomorrow. I expect the losses to be mich higher ( higher delta) due to the increased IR.

 

[AAKEE]

I heard they're full of holes

Actually more like som much capacity that they are swollen

 

[AAKEE]

As a reference one drive to work in august with warm battery all the way had a delta of 50.2kWh on the nominal full pack and 50.05kWh used on the energy screen.

 

[AlanSubie4Life]

I expect the losses to be mich higher ( higher delta) due to the increased IR.

Very exciting! This is the kind of riveting content I will come back for on this site.

 

[AAKEE]

Very exciting! This is the kind of riveting content I will come back for on this site.

The trip home was a flop.

There was supercold rain in the evening/night so I had to heat the cabin be able to open doors etc. which also heats the battery so it was 4.5C starting the trip home.
Ended up using 33.2kWh on the trip screen, and 33.2kWh delta on the NFP so no cold joy today.

 

[JCtx]

A quick related question. Read that Tesla was caught 'cheating' by exaggerating the range on the screen, meaning they'd show 'x' range, when in reality the car was only capable of 'x - y', with the 'y' being as much as 30 miles. In other words, the car's algorithm was deducting 1+ miles for every mile traveled in a seamless way, so no way for owners to know what was going on. Since I sold my '21 LR, I stopped following this forum, but since I'm considering getting back with a new M3P (if I catch a good inventory deal at the end of the year), just wondering if those antics (not any different than Apple messing with battery life) are over now. By the way, I always used the '%' way, rather than miles, but it probably was the same thing with %. Maybe that's why the range was decreased from the 353 on my LR to 333 now (I only got 200+ on the highway), but just want to make sure. Thanks gang.

 

[AlanSubie4Life]

Maybe that's why the range was decreased from the 353 on my LR to 333 now

It decreased from 358 (not 353 - it used to be) to 333 due to them introducing a smaller pack. We don’t have the details because there is not a detailed EPA document yet. It probably did worse in 5 cycle testing so the baseline ~335 (aka 358 - it is the same; 335/358 are just in different frameworks, assuming a scalar of about 0.75 which I think is about correct for this vehicle.) with the 82.1kWh was reduced a bit, and then the scalar expansion was smaller. So something like 324 with the new 78.8kWh pack expanded by 0.72/0.7 to 333 or so. But hard to know for sure.

The energy to 0 is 95.5% of the EPA energy. It’s not cheating, it just makes those “miles” (energy) 4.5% less energetic.

There is no exaggeration on the screen. It just shows you your energy remaining. It doesn’t tell you what your range is.

 

[ran349]

There is no exaggeration on the screen. It just shows you your energy remaining. It doesn’t tell you what your range is.

He might have been talking about the energy screen, in which case the screen is exaggerating your available miles. Because if you are driving at EPA energy efficiency, the screen will tell you that you will achieve rated miles, when in fact, you are getting 95.5% of that.

Whether that constitutes cheating or not is debatable, but it is misleading at the very least.

 

[AAKEE]

He might have been talking about the energy screen, in which case the screen is exaggerating your available miles. Because if you are driving at EPA energy efficiency, the screen will tell you that you will achieve rated miles, when in fact, you are getting 95.5% of that.

To be very precise, the energy screen do not exaggerate the available range.

The EPA tests (and WLTP) drives until the car stops. The car shows the remaining range until the car stops at full SOC.
During the drive the car hides 4.5% of the total SOC range (to create the buffer/margin) but if you continue to drive you will get tge range Tesla shows (using the appropriate consumtion).

 

[Bouba]

Did Tesla do an EPA certification for every single battery varient that it’s used ?...or is the battery capacity divided by the energy efficiency enough ?

 

[AAKEE]

Did Tesla do an EPA certification for every single battery varient that it’s used ?...or is the battery capacity divided by the energy efficiency enough ?

They would need to do a new test, changing to another battery type might cause the efficiency to change.

I checked a BMW EPA test the other day.
Seeing the cold depleting test made me afraid of the darkness
The battery output reduced some 25% or so in cold. (And then the extra needed energy for heating and driving was not counted so the real range loss…

 

[ran349]

To be very precise, the energy screen do not exaggerate the available range.

The EPA tests (and WLTP) drives until the car stops. The car shows the remaining range until the car stops at full SOC.
During the drive the car hides 4.5% of the total SOC range (to create the buffer/margin) but if you continue to drive you will get tge range Tesla shows (using the appropriate consumtion).

You would have to continue driving after the car reaches 0% SOC to reach the EPA miles, and even then there is no guarantee you would get all the EPA miles if you continue to drive below 0%. There are many cases of people being stranded on the side of the road for trying this.
So yes, it is misleading, and could get you into a problem situation if you assume you can continue driving much below 0%.
In some cases you might be able to use the complete buffer but you shouldn't assume that.

 

[AlanSubie4Life]

Because if you are driving at EPA energy efficiency, the screen will tell you that you will achieve rated miles, when in fact, you are getting 95.5% of that.

Yeah it is possible this was the reference, but this discrepancy also applies to the displayed range in the vehicle as I mentioned. Aside from what @AAKEE said which is correct, to your point about the energy line - it is not a fixed percentage actually, as the energy line is always 5Wh/mi +4.5% above where it needs to be to get mile-for-mile rolloff (e.g. in a Model 3 2018 if you drive at 234Wh/mi that will get you the displayed range to 0%. But the line is at 250Wh/mi (1/0.955*234Wh/mi + 5Wh/mi). Of course if you drive at 250Wh/mi the projected range (which is also misleading as you point out since it is best not to touch the buffer) will not match displayed range…but anyway wanted to address your point).

Another way to express this is to ignore the energy screen (the consumption page specifically) except for battery capacity calculations. It’s dumb. Even if it worked perfectly, with no “exaggeration” it is quite useless for telling your range unless you live on a windless plain.

 

[JCtx]

During the drive, the car hides 4.5% of the total SOC range (to create the buffer/margin). But if you continue to drive, you will get the range Tesla shows.

That might be the discrepancy, which I didn't know. But it's still confusing, since after a full charge, the range (or %) shown is the max possible. So what you're saying is, after that point, the range is reduced 4.5%, so it shows 0 when you still have 4.5% left? Just to understand correctly. Thanks.

 

[DuncanM]

That might be the discrepancy, which I didn't know. But it's still confusing, since after a full charge, the range (or %) shown is the max possible. So what you're saying is, after that point, the range is reduced 4.5%, so it shows 0 when you still have 4.5% left? Just to understand correctly. Thanks.

Typically there's a buffer below 0 SOC but the achievable range from the buffer might be not be Predictable. I've found that my M3 will get it's EPA range when driving at 60-65mph on reasonably flat roads at moderate temperatures.

 

[AAKEE]

That might be the discrepancy, which I didn't know. But it's still confusing, since after a full charge, the range (or %) shown is the max possible. So what you're saying is, after that point, the range is reduced 4.5%, so it shows 0 when you still have 4.5% left? Just to understand correctly. Thanks.

Yes, thats right.

 

[KenC]

A quick related question. Read that Tesla was caught 'cheating' by exaggerating the range on the screen, meaning they'd show 'x' range, when in reality the car was only capable of 'x - y', with the 'y' being as much as 30 miles. In other words, the car's algorithm was deducting 1+ miles for every mile traveled in a seamless way, so no way for owners to know what was going on. Since I sold my '21 LR, I stopped following this forum, but since I'm considering getting back with a new M3P (if I catch a good inventory deal at the end of the year), just wondering if those antics (not any different than Apple messing with battery life) are over now. By the way, I always used the '%' way, rather than miles, but it probably was the same thing with %. Maybe that's why the range was decreased from the 353 on my LR to 333 now (I only got 200+ on the highway), but just want to make sure. Thanks gang.

A link to the story on Tesla caught "cheating" would be helpful. Others have suggested that you may be referring to the bottom buffer, but that wouldn't be 30 miles worth of buffer. As for the Apple messing with battery life, I'm not sure what you mean. If you're referring to them throttling the processor speed, so that the phone wouldn't do random shutdowns, when low on charge and under heavy load, I think the problem was not informing the user that they were throttling the processor to prevent random shutdowns. Not very nefarious, just not very informative.

 

[JCtx]

Sorry to disappoint you, but although I don't believe nearly anything I read, I don't keep track of the stories I do. It's the internet, not a dissertation. All I can tell you is the range on my LR was WAAAAY lower than advertised under every condition, so seemed plausible to me. And could have been that 'buffer', for all I know. And Apple was sued (and settled out of court, and offered owners free battery replacement... which I got) for doing something to decrease battery life, to force owners to upgrade to a new phone. If you care that much about both stories, search. And VW cheated with the diesel emissions, and got caught too. Unless you're in kinder garten, it's nothing new.