Almost 15% range loss Model 3 Awd

[TimothyHW3]

I just did a 17.1 mile segment at 340 Wh/mi and used 9 percent capacity. If my battery is degraded for whatever reason to 281/310 = 90.6% capacity remaining, this would be approximately 69.8 kWh. The equivelent 9 percent of 69.8 kWh Is about 6.3 kWh. Yet my display tells me I used 17.1 mi x 340 Wh/mi = 5.8 kWh, which is very roughly an 8 percent difference. So I have a supposed degraded battery capacity, plus my usage and efficiency disagrees by an additional notable margin.

It seems like this thread has some people that are talking past each other. Something has changed in SW recently that is causing a lot of confusion.

Did you read any of my comments? If not please do. I explained exactly why this happens...You are about 40% above EPA rating. This might be A)due to heavy foot B) colder temps in Colorado. Whatever the reason, there is some "capacity" being lost somewhere while you were driving.
To know your degradation, you have to charge to about 100% and drive at constant speed and get EPA rating 245Wh/m for about 270-280miles. If you can do that you are fine...
Please also read my comments to understand why 100% is not 310 miles, but about 300 miles(buffer!) when brand new and still means 0% degradation and about 290 when degrading after a while and going down.

Also, not sure about V10 but no software update changed anything on the BMS capacity side so far.

 

[flybuzz]

Yes have seen that video several times and it seemed like a great solution to try out. However as previously stated my SC does not think there's is anything wrong with my battery, so I think it will be had to make them do the reset.

I think that's what upper management told SC as a standard boiler plate response so they don't have to bother wasting time and money replacing it. Replacing battery is expensive and they are trying to drag it out until you are out of warranty and force you to buy new one. I have already lost about 7% on my midrange and still the first year of ownership. Tesla support also told me the exact same thing, they see no issues and closed my ticket. I also asked BMS reset, they told me they don't offer such service. I think up to a point you have to draw the line and see if you can get it to lose 30% range and force them to replace the battery.

 

[brianman]

2. I don't know my 100%, because I rarely do 100%, but last I checked it was 497. Based on my estimate it should be 494-495 now.

Units here are kind of important.

 

[TimothyHW3]

Obviously km...

 

[Wizard2416]

Tl;tr. Just switch to percentage and call the day.

 

[299792458]

That small a discharge, it is very hard to extrapolate accurately.

However: I would expect a 17.1mi*340Wh/mi = 5.81kWh discharge to result in 5.814kWh/230Wh/rmi = 25.3 rated miles used.

This is 9% of 281 rated miles. (25.3rmi /0.09 = 281 rated miles)

So that all lines up. Perfectly. However, to some extent it is happenstance that it lined up this time - typically a 9% discharge will not project out so perfectly to what you think your 100% is.

In my view (yes, we are definitely talking past each other, though I am trying not to; I am trying to base things on hard observable (for the general user) data), what this means for you:

Maximum discharge on the trip meter possible (to 0 rated miles): 281rmi * 230Wh/rmi = 64.6kWh

Maximum charge event energy (from 0 rated miles, not below): 281rmi * 245Wh/rmi = 68.8kWh.

So your battery (not including the reserve) has ~69kWh of energy (90.6% of 75.9kWh, a new battery). Your battery appears to be lacking about 9.4% of its original capacity.




Looks like you used 77kWh for this calculation. I would use 75.95kWh, 310rmi*245Wh/rmi (you can say 76kWh obviously).

281rmi(now)/310rmi(orig)*75.95kWh = 68.8kWh (matches the number extrapolated above of course)



I believe you. Your numbers make perfect sense for an AWD. Happened to extrapolate perfectly this time, but yes, a longer discharge would typically be desired (or just quote rated miles used rather than % to be able to do the calculations - the resolution is better so less rounding inaccuracy).

So Im too lazy to go out and look at this right now, but when did rated Wh/mi change to 230 for a P3D? I thought this was closer to 250 (based on simple battery capacity and range rating in miles). I am pretty sure the energy graph showed somewhere around this as well.

 

[299792458]

Did you read any of my comments? If not please do. I explained exactly why this happens...You are about 40% above EPA rating. This might be A)due to heavy foot B) colder temps in Colorado. Whatever the reason, there is some "capacity" being lost somewhere while you were driving.
To know your degradation, you have to charge to about 100% and drive at constant speed and get EPA rating 245Wh/m for about 270-280miles. If you can do that you are fine...
Please also read my comments to understand why 100% is not 310 miles, but about 300 miles(buffer!) when brand new and still means 0% degradation and about 290 when degrading after a while and going down.

Also, not sure about V10 but no software update changed anything on the BMS capacity side so far.

This thread is becoming too much. Please stop making assumptions about those you reply to.

[Exit stage left]

 

[AlanSubie4Life]

So Im too lazy to go out and look at this right now, but when did rated Wh/mi change to 230 for a P3D? I thought this was closer to 250 (based on simple battery capacity and range rating in miles). I am pretty sure the energy graph showed somewhere around this as well.

I'm sorry you were turned off by this thread. I understand!

Well, as you say, in this thread, people are talking past each other.

But, what I am saying, and what I have seen (I have a P3D) is:

For charging, on the charging screen: 245Wh/rmi

For discharging, on the trip meter: 230Wh/rmi (this is an estimate; it MAY be as high as 234Wh/rmi, but I haven't been able to measure that accurately - I always get right around 230Wh/rmi).

That's all you really need to know to explain your observations - happy to go through more data, if you gather more.

My lifetime average consumption is about 280Wh/mi on the trip meter, so that means according to above my lifetime average "range" is about 250 miles (my battery is about 307 rated miles at 100%). 307rmi*(230Wh/rmi)/(280Wh/mi) = 252 miles

True range is likely a lot less than that as I'm not going to get 280Wh/mi traveling at 80mph! I'll find out tomorrow. I expect to be able to go about 200 miles between charges (350Wh/mi).

 

[299792458]

I'm sorry you were turned off by this thread. I understand!

Well, as you say, in this thread as you say, people are talking past each other.

But, what I am saying, and what I have seen (I have a P3D) is:

For charging, on the charging screen: 245Wh/rmi

For discharging, on the trip meter: 230Wh/rmi (this is an estimate; it MAY be as high as 234Wh/rmi, but I haven't been able to measure that accurately - I always get right around 230Wh/rmi)

That's all you really need to know to explain your observations - happy to go through more data, if you gather more.

I can definitively say that in the past, on many, many occasions, my calculations for capacity and range based on displayed usage and distance traveled were very well within margin of error based on pack size of 77 kWh and rated range of ~250 Wh/mi.

 

[AlanSubie4Life]

I can definitively say that in the past, on many, many occasions, my calculations for capacity and range based on displayed usage and distance traveled were very well within margin of error based on pack size of 77 kWh and rated range of ~250 Wh/mi.

If I get a chance I'll post my data while at the Superchargers tomorrow.

A ~310 mile range giving...

77kWh and ~250Wh/rmi can also be explained with....

76kWh and 245Wh/rmi

I can't explain how your displayed usage would have aligned though. I've never seen it align with the charging event data.

 

[299792458]

If I get a chance I'll post my data while at the Superchargers tomorrow.

Cool, and I appreciate the thoughtful conversation. No reason why reasonable people can't philosophize about these seemingly disparate data points.

 

[ajdelange]

Based on the sub-forum and post title, he's talking about a Model 3 not a Model S.

Yes. I know. I must be dislexic or something because I am always writing S when I mean 3 and conversely. That's the worst feature of this site. You can't correct and error unless you catch it within an hour.

 

[brianman]

Yes. I know. I must be dislexic or something because I am always writing S when I mean 3 and conversely. That's the worst feature of this site. You can't correct and error unless you catch it within an hour.

Ok but 100 kWh doesn't make sense if you're talking about a Model 3.

 

[TimothyHW3]

This thread is becoming too much. Please stop making assumptions about those you reply to.

Well, sorry, but it doesn't seem you did read any of my posts, because right above your question I explained what the total capacity including buffer is, why the buffer is calculated in the total rated range(310), but when you drive it actually isn't and you only have 290 or so real range from 0-100% and about the heat loss when driving at higher consumption above the EPA rating.

To explain the heat loss while driving in more easier terms,because some people don't understand it.

Think of it like this: you have a full glass you are transporting while drinkng. If you walk very, very slowly and drink from it, the amount you drink will be the amount you removed from the glass. But if you run fast WHILE drinking, you will spill some water in addition to the amount you drank.

So if you have 73kWh available and you spent 7.3kWh according to the BC trip meter, if you drove a flat out, you would have spent 7.3kWh for the motor, AC and such, but in reality you also "spilled"(heat loss) some kWh while driving, and thus you spent 10% but maybe spilled 5% more. And the BC will show 15% missing(an example - exact number depends on battery available and the amount of heat loss).

BC trip meter doesn't show the heat loss in the trip meter kWh used, but the % gauge calculates based on total available kWh capacity left. So there will be discrepancy.

 

[TimothyHW3]

And to fully explain the discrepancy between % and kWh used, I will lean on my example:

The kWh used is the water you drank(the meter is inside the mouth)
The battery % gauge is the amount left in the glass.

And if you spilled some water, there is no meter for that.

So we have two indicators - the meter inside your mouth showings kWh used, % gauge which measures just how much water is left in the cup.

The only way to understand the amount of "spilled water" heat loss is to know the full capacity of the glass, get the % gauge left based on the capacity of the glass when you filled it in and add the amount you drank to it. The difference is then the heat loss.

1 Gallon water in the glass at full(73kWh for example, without buffer!)
25% went into your mouth
25% went outside(heat loss)
You have 50% showing on the % left, but the trip meter shows only 18.25 kWh used(25%*73)

 

[ajdelange]

Ok but 100 kWh doesn't make sense if you're talking about a Model 3.

Yes, thanks. I understand that too. Anything else?

 

[ajdelange]

BC trip meter doesn't show the heat loss in the trip meter kWh used, but the % gauge calculates based on total available kWh capacity left. So there will be discrepancy.

And if you spilled some water, there is no meter for that.

The car measures the current drawn from the battery and the battery voltage. The product of the two is the power being drawn from the battery at any instant of time and its integral (sum) over a time interval is the energy drawn from the battery over that interval. The integral of current over the interval is the total charge drawn from the battery. The traction current flows through the inverters and then through the motor stator. The inverters have resistance, even when the transistors are switched fully on, and take time to switch on so heat is dissipated in them. The amount of heat is proportional to the square of the current so you produce, and lose, more when you load the motor heavily and so efficiency goes down. The motor windings also have resistance and there is I^2R loss in them too which also increases with load. Thus this same current that produces the rotating magnetic field (which transfers power to the rotor and thence the wheels) also produces heat and it is very clear that the displayed energy consumption is the total energy consumption including that lost to heat.

Since both current and voltage can be measured quite accurately so can total energy and charge drawn from the battery. The car knows the charge/discharge characteristic of the battery (voltage vs charge) one can, by looking at the slope of the charge added vs voltage observed during charging, deduce the capacity of the battery.

Caveat: I am not privy to the details of the algorithms used by Tesla's BMS in estimating SoC so the last paragraph is largely speculation based on common sense. But the earlier paragraphs are not. And indeed while it is not possible to separate the current which produces heat from the current which provides traction one could estimate it as one knows rotor speed and torque. But it would make no sense to do that. We want to know the total energy consumed in going a mile.

 

[TimothyHW3]

The car measures the current drawn from the battery and the battery voltage. The product of the two is the power being drawn from the battery at any instant of time and its integral (sum) over a time interval is the energy drawn from the battery over that interval. The integral of current over the interval is the total charge drawn from the battery.

So far so good, I am not arguing to that. But so far the heat loss is not in this calculation. And the regen as well.

The traction current flows through the inverters and then through the motor stator. The inverters have resistance, even when the transistors are switched fully on, and take time to switch on so heat is dissipated in them. The amount of heat is proportional to the square of the current so you produce, and lose, more when you load the motor heavily and so efficiency goes down. The motor windings also have resistance and there is I^2R loss in them too which also increases with load. Thus this same current that produces the rotating magnetic field (which transfers power to the rotor and thence the wheels) also produces heat and it is very clear that the displayed energy consumption is the total energy consumption including that lost to heat.

I hate to argue with the scientific explanation you just did, but this doesn't seem to be the way the BMS calculates consumption shown under "used" for the trip.

Caveat: I am not privy to the details of the algorithms used by Tesla's BMS in estimating SoC so the last paragraph is largely speculation based on common sense. But the earlier paragraphs are not. And indeed while it is not possible to separate the current which produces heat from the current which provides traction one could estimate it as one knows rotor speed and torque.

And from the observations, this is not what the BMS is doing. I think they don't want to do the hard work of calculation and messing it up, especially when 99% of their customer base will never drive above 75-80mph and experience massive heat loss.

This is evident by the SOC readings from the CAN bus on a high-speed stretch, which doesn't match the kWh used in the trip meter, based on % of available capacity. I am doing another road trip in a while and will try to capture exactly this discrepancy I am discussing when I drive above 100mph.

 

[turtlesz]

Same issue in our family. Our model 3 has 22k miles and still gets charged to 313. However the newer one my sister drives has 14k miles and only charges to 278. Wh/hr lower in her car too. Both are LR RWD cars purchased in 2018.

 

[gecko10x]

Same issue in our family. Our model 3 has 22k miles and still gets charged to 313. However the newer one my sister drives has 14k miles and only charges to 278. Wh/hr lower in her car too. Both are LR RWD cars purchased in 2018.

Curious if you know the charging regimen for each?