Error in power consumption or battery issue?

[Noivilbo]

Hi all,

I have a Tesla S plaid 2023, which should have a 100 KwH battery.
The stats shown in the "trips" view indicate how much power I've used and at which rate.
For example 50 KwH used / 200 km driven / 250 KwH/Km consumption.

If I start from a full charge, and I have used 50 KwH do drive my 200 km, my battery percentage should be 50%, right? (50kwh used of the 100 kwh battery capacity)
In practice, my battery is drained a lot more - it shows 42% left, rather than 50% (I.e. more than 15% extra loss...).

Is this normal, because a 100 kwh battery loses >15% when you actually want to use the power? That seems a lot?
Or is there an issue with my battery?

Many thanks!!

 

[ucmndd]

Or is there an issue with my battery?

Assuredly not.

It’s just the way it is.

 

[AAKEE]

Hi all,

I have a Tesla S plaid 2023, which should have a 100 KwH battery.
The stats shown in the "trips" view indicate how much power I've used and at which rate.
For example 50 KwH used / 200 km driven / 250 KwH/Km consumption.

If I start from a full charge, and I have used 50 KwH do drive my 200 km, my battery percentage should be 50%, right?

Nope.

The battery is 99.4kWh ”full pack when new” but rarely goes above 98kWh as I see it.
From that 4.5% is buffer below 0%, so if you have 98kWh capacity, the ”usable” above 0% is 93.6 kWh.

So in that case, 50% equals about 46.8 kWh.

Many people using high SOC (70-90%) most ofcthe time, and this means calendar aging will degrade the battery around 5% the first year (depends on temperature etc, but 5% gice or take).
This means that you have around 44.5 kWh available for 50% SOC use after about one year.

Also, driving faster than ~ 50-55mph will cause the heat losses from the battery to be higher, which means a small part of the normally available energy will be lost in heat (making the 44.5kWh maybe be 43.5-44kWh). The faster you drive the more losses.

(50kwh used of the 100 kwh battery capacity)
In practice, my battery is drained a lot more - it shows 42% left, rather than 50% (I.e. more than 15% extra loss...).

If you used 58% for 50 kWh on a single drive your battery has about (50/0.58)/0.955 = 90.3kWh total capacity.

My Plaid battery is at about 97.5 kWh total capacity today (10 month since build, 7 months since I got it).
I charge to a lower SOC than most people and i see that my Plaids battery capacity is higher than most other cars.

 

[AAKEE]

Here’s some sources:

Full pack when new, the ”marked size”, hardcoded in the battery.
Also most often close to the energy the EPA-test did get out of the pack. For Plaid that was 99.4 and 99.3 kWh (two tests, differebt wheels).

Nominal full pack, the BMS estimate of the capacity.
Nominal remaining, the BMS estimate of the current energy in the pack.

My highest note, about one month into the ownership.

You can get the whole number out of the pack, as described above with the EPA test.
The buffer of 4.5% is below 0% on the display but you can use it.

As I wrote in the last post, most people do not get the capacity value above 97 kWh, and it declines rather fast after a few months, so perhaps about 94kWh after some time.

 

[Noivilbo]

Alright - many thanks for the detailed explanations in any case!

Tbh, it's a tad dissapointing, so all the stats on how much KwH I consume are not necessarily reliable to estimate my total range

 

[ran349]

Here’s some sources:

Full pack when new, the ”marked size”, hardcoded in the battery.
Also most often close to the energy the EPA-test did get out of the pack. For Plaid that was 99.4 and 99.3 kWh (two tests, differebt wheels).
View attachment 1017483

Nominal full pack, the BMS estimate of the capacity.
Nominal remaining, the BMS estimate of the current energy in the pack.

My highest note, about one month into the ownership.
View attachment 1017485

You can get the whole number out of the pack, as described above with the EPA test.
The buffer of 4.5% is below 0% on the display but you can use it.

As I wrote in the last post, most people do not get the capacity value above 97 kWh, and it declines rather fast after a few months, so perhaps about 94kWh after some time.

Your max full pack was 98.4 and currently is at 97.5. How much change have you seen in the corresponding full rated range in miles for those two cases? Do you still see the full rated range?

 

[AAKEE]

Your max full pack was 98.4 and currently is at 97.5. How much change have you seen in the corresponding full rated range in miles for those two cases? Do you still see the full rated range?

Still full range.

The degradation threshold might be ~96-97kWh.

My pack (or BMS actually) goes up and down between 97 and 98 kWh.

Every full charge have shown full range so far (560km).

 

[AlanSubie4Life]

Tbh, it's a tad dissapointing, so all the stats on how much KwH I consume are not necessarily reliable to estimate my total range

If you pay really close attention you can figure out your pack energy. But have to meter a very long and continuous discharge, if you are above the degradation threshold. You have to compare rated mile use to energy consumed and calculate energy per rated mile, without any stops at all. It requires three significant digits for the various elements going into the calculation. This is not necessary at all if your car is showing rated range loss.

Anyway, once you know that, you can figure out your total range for a given consumption. (And can include margin if you want.)

But anyway it is all explained above.

But realistically you just drive according to the nav and make sure to leave adequate margin. It takes into account these factors (not sure whether it actually does take into account energy above the degradation threshold (not aware of any tests), but then it would just mean you have more margin).

 

[ran349]

Still full range.

The degradation threshold might be ~96-97kWh.

My pack (or BMS actually) goes up and down between 97 and 98 kWh.

Every full charge have shown full range so far (560km).

According to the Tesla website, the plaid with 21" has an EPA range of 320 miles which equals about 515 km. Do you know what standard they use in your car to get 560 km (348 miles) for full range? That's a pretty big difference. Is that a realistic value under typical driving conditions?

 

[AAKEE]

According to the Tesla website, the plaid with 21" has an EPA range of 320 miles which equals about 515 km. Do you know what standard they use in your car to get 560 km (348 miles) for full range? That's a pretty big difference. Is that a realistic value under typical driving conditions?

The 320 miles are very recently changed.

My MSP ’23 has 348 mi EPA range with the 21”. And it is 396 mi with 19”.
Thats why I read 560km.

 

[AAKEE]

s that a realistic value under typical driving conditions?

~ 500 km summer highway driving (310 mi) 100-0% displayed. (Of course speed dependant).

 

[Noivilbo]

If you pay really close attention you can figure out your pack energy. But have to meter a very long and continuous discharge, if you are above the degradation threshold. You have to compare rated mile use to energy consumed and calculate energy per rated mile, without any stops at all. It requires three significant digits for the various elements going into the calculation. This is not necessary at all if your car is showing rated range loss.

Anyway, once you know that, you can figure out your total range for a given consumption. (And can include margin if you want.)

But anyway it is all explained above.

But realistically you just drive according to the nav and make sure to leave adequate margin. It takes into account these factors (not sure whether it actually does take into account energy above the degradation threshold (not aware of any tests), but then it would just mean you have more margin).

Yeah indeed, was doing this exactly - calculating how much extra loss I have to make sure I know the real range.
But the NAV does indeed give a very good estimate in terms of % left when arrived (achieveable if I drive eco-friendly).
Just pretty stupid that it knows the real range when calculating the expected battery charge left upon arrival, while the "KM I could still drive" based on my battery are always horrendously overestimated

 

[Rocky_H]

Just pretty stupid that it knows the real range when calculating the expected battery charge left upon arrival, while the "KM I could still drive" based on my battery are always horrendously overestimated

I think it probably makes sense, rather than being "stupid". People are probably mostly driving around town for their past 30 miles. That lower speed local road driving--higher efficiency--so the projected remaining miles will show high, based on the lower speeds projected into the future. Then someone wants to plot a predicted traveling road trip: high speed interstate driving = much higher wind resistance = lower efficiency. So of course the estimate on range will be lower.

One is predicting from the past, and the other is predicting for the future, and they are usually very different driving types.

 

[islandbayy]

Hi all,

I have a Tesla S plaid 2023, which should have a 100 KwH battery.
The stats shown in the "trips" view indicate how much power I've used and at which rate.
For example 50 KwH used / 200 km driven / 250 KwH/Km consumption.

If I start from a full charge, and I have used 50 KwH do drive my 200 km, my battery percentage should be 50%, right? (50kwh used of the 100 kwh battery capacity)
In practice, my battery is drained a lot more - it shows 42% left, rather than 50% (I.e. more than 15% extra loss...).

Is this normal, because a 100 kwh battery loses >15% when you actually want to use the power? That seems a lot?
Or is there an issue with my battery?

Many thanks!!

Trips only displays power used while the vehicle is pretty much, in motion. Power used while "idle", such as pre-conditioning, systems vampire losses, sentry mode, etc... are not calculated in.

 

[AAKEE]

while the "KM I could still drive" based on my battery are always horrendously overestimated

You know that the km shown at the battery never was ment to try to show the real range remaining?
It is a display of energy remaining divided with a fixed consumption (the EPA-consumption).

 

[AAKEE]

Yeah indeed, was doing this exactly - calculating how much extra loss I have to make sure I know the real range.

There is ways to estimate the capacity with a very good precision.
My Plaid’s BMS pissed on me when i got the car with 95.7kWh capacity (out of 99.4kWh). I suspected that it was off, so I made the same calc I had tested on my first Tesla with good result.

For example, using 50% of a battery that delivers 50kWh during this time will have a capacity of 100 kWh (50/0.5).

For Teslas we need to recalculate the SOC to true numbers, as there is a 4.5% buffer below zero.

There is a few things needed to make sure:
To let the car sleep a little before the drive and after the drive to make sure the BMS SOC is correct (the BMS Updates the SOC after a drive when the battery are relaxing).

I took some data from a 240 km drive yesterday.

Nominal remaining 97.1 before, 41.7 after.
Delta Nominal remaining 55.4 kWh.

Start SOC = 100.0%
End SOC = 40.5% which is 43.18% True SOC.
Delta SOC = 56.82%

55.4/0.5682 = 97.5 kWh, which is quite close to the BMS estimate.

Not having SMT, the SOC in whole numbers can be used, but then a larger capacity of the battery should be used to minimize the error from rounded SOC.
Also, range shown in km/mi can be used as it offers about 0.2% precision in SOC numbers.