75D...Don't care about Miles/kM, only kwH

[NoBeard]

So wondering. If you set the system to display % not distance, Charge to 100% and you drive until the remaining battery is 50%, in the Trip screen how many kwh does it say you've consumed?
I'll try and post a photo of my screen as soon as I have done exactly that.

 

[P85_DA]

This will vary as car doesn’t show phantom drain

 

[NoBeard]

This will vary as car doesn’t show phantom drain

To be more clear, in a single drive without the car sitting idle for any time, start at 100%. How many kwh have you consumed by the time you get to 50%?

 

[Mewtwo]

To be more clear, in a single drive without the car sitting idle for any time, start at 100%. How many kwh have you consumed by the time you get to 50%?

I think it depends on your driving style. If you drive conservatively and keep consumption around rated value, I believe you will get close to 50% of the total kWh (for 75D it’s around 72.4?)
Alternatively if you drive like you stole it, Hard acceleration etc, You will get a lot less usable kWhs.

 

[_jmk]

I get to around 66-67kWh used for full charge. 100D seems to be getting 20kWh or so more.

 

[NoBeard]

I think it depends on your driving style. If you drive conservatively and keep consumption around rated value, I believe you will get close to 50% of the total kWh (for 75D it’s around 72.4?)
Alternatively if you drive like you stole it, Hard acceleration etc, You will get a lot less usable kWhs.

Hmmm. I can see that by driving it aggressively (or keeping it super hot or super cold inside) the km achieved will fall dramatically, but the amount of usable energy decreases? You use the energy one way or another, either it's there or it's not. If I fill a measuring cup with a litre of water and pour it out slowly or pour it out quickly, when the gauge reads 50% there should be 500 ml left in the cup with the other 500 ml gone. I may have wasted some water by splashing it about when pouring, but I've still used it and it will still be measured as gone. Aggressive usage should make the wh/km go up and the km driven go down, but the % vs used/remaining should be a constant % of total available.

I too had read 72.4 usable in many places, which is why I'm wondering why I seem to have only about 63 kwh usable. See attached images...
Started with 100%, drove without stopping at a reasonable usage rate averaging 218 wh/km.

 

[NoBeard]

I also thought it interesting that when Tesla sold the software locked 60, apparently it had about exactly what my car seems to have available.

 

[_jmk]

For me to get to ’67kWh used’ I have to keep the overall consumption below 200wh/km. 68 is achievable with 189wh/km which means 92km/h or thereabouts in my driving.

 

[Hugh-SG]

Also depends on if your trip during this trail you are attempting goes up any steep hills. Extended driving up into a mountain pass with a longer uphill then down hill, will dramatically affect the power consumed.

Thus why there is not a linear direct comparison of charge remaining percentage to distance traveled except on absolutely flat terrain for the whole duration of the power usage and one is gentle on the throttle..

Example.... with my M-X, I drove from Kelowna 67km up to Big White Mtn. I used 100km of energy to get up there. The return drive of 67km was 70% down hill, so I only used 20km of energy to travel the same 67km.

2nd example. Hope TSC to Merritt TSC in British Columbia last month. 131km according to my GPS but in +5c conditions with rain I used 200km of energy to climb up the Coquahala (Highway from Hell) at 120km/ph. I also had the cabin heater on. Did same trip two weeks ago at 14'c and only needed 180km of energy to go 131km.

Food for thought, Cheers, Hugh

 

[Mewtwo]

Hmmm. I can see that by driving it aggressively (or keeping it super hot or super cold inside) the km achieved will fall dramatically, but the amount of usable energy decreases? You use the energy one way or another, either it's there or it's not. If I fill a measuring cup with a litre of water and pour it out slowly or pour it out quickly, when the gauge reads 50% there should be 500 ml left in the cup with the other 500 ml gone. I may have wasted some water by splashing it about when pouring, but I've still used it and it will still be measured as gone. Aggressive usage should make the wh/km go up and the km driven go down, but the % vs used/remaining should be a constant % of total available.

I too had read 72.4 usable in many places, which is why I'm wondering why I seem to have only about 63 kwh usable. See attached images...
Started with 100%, drove without stopping at a reasonable usage rate averaging 218 wh/km.View attachment 415010 View attachment 415011

The thing is, energy stored in the battery is very different compared to water in a cup. Here is a good explanation:
“The discharging rates affect the rated battery capacity. If the battery is being discharged very quickly (i.e., the discharge current is high), then the amount of energy that can be extracted from the battery is reduced and the battery capacity is lower. This is due to the fact the necessary components for the reaction to occur do not necessarily have enought time to move to their necessary positions. Only a fraction of the total reactants are converted to other forms, and therefore the energy available is reduced.

Alternately, if the battery is discharged at a very slow rate using a low current, more energy can be extracted from the battery and the battery capacity is higher.”

Model x is rated at around 190w/km, so your 218w/km is actually 15% more than the rated. Also, remember the computer does not account for energy spent when car is not moving, so it may not count all the energy spent. All these factors caused you seeing reduced kWh compared to the standard 72.4.

 

[NoBeard]

The thing is, energy stored in the battery is very different compared to water in a cup. Here is a good explanation:
“The discharging rates affect the rated battery capacity. If the battery is being discharged very quickly (i.e., the discharge current is high), then the amount of energy that can be extracted from the battery is reduced and the battery capacity is lower. This is due to the fact the necessary components for the reaction to occur do not necessarily have enought time to move to their necessary positions. Only a fraction of the total reactants are converted to other forms, and therefore the energy available is reduced.

Alternately, if the battery is discharged at a very slow rate using a low current, more energy can be extracted from the battery and the battery capacity is higher.”

Model x is rated at around 190w/km, so your 218w/km is actually 15% more than the rated. Also, remember the computer does not account for energy spent when car is not moving, so it may not count all the energy spent. All these factors caused you seeing reduced kWh compared to the standard 72.4.

Almost had me believing this, seems very rational and scientific.... Until today when I ran a trip starting at 90% and did some hypermile driving to keep the kwh/km down.
I think the rating is actually 198 wh/km, as this image shows the dashed usage line at 197 below the solid rated line and when it goes up one the lines merge...

So when the battery remaining was at 40%, so I'd used 50% of the battery, here was the usage...

Pretty much exactly the same as the 31.8 the other day.

So I'll try again tomorrow as I need to do the same trip, only I'll charge to 100% to test just in case that was an issue.

Not sure I've heard any explanations that hold water yet except that maybe we only have 63 kwh of usable on board.

 

[gangzoom]

Not sure I've heard any explanations that hold water yet except that maybe we only have 63 kwh of usable on board.

Based on reported kWh used and dash display of SOC, I have NEVER seen more than 68kWh 'usable' on our 75D X. Most of the time the calculation shows 65-67kWh.

BUT the BMS clearly isn't 100% accurate, I've seen the dash % go up (and down) by 2-3% within 10 seconds on a few occasions.

Only way to know for sure is to run from 100-0%.

Below is starting at 100%, so 66kWh if 0% displayed is truly 0%.

 

[NoBeard]

So I kept the car at 10% under the rated wh/km to see how much battery we could get available, to put to rest the chemical usable science as the explanation. It may be a difference, but that difference is slight, nothing like explaining the difference between 75 and the results achieved. At 176 wh/km from 100%>50% the total used was 32.2 indicating 64.4 total usable. Even given the variability of the display it's highly unlikely that the often quoted 72.4 kwh of available battery.
Seems that the 64-66 kwh reported by @_jmk and @gangzoom seem a lot more realistic to me.
So if there really is only 66 available, and the rated wh/km is 198 then the range at rated usage is quite different than if there were 75 kwh in the tank.
75000/198=378
66000/198=333
So at the 176 wh/km that I achieved on this trip I got 182.4 km, so the range would be 364.8 km. So running at about 10% under rated added about 10% more to the 333 calculation.

Interesting. My final "thought" would be that there is a bunch in the tank still when it reaches 0%, like the 45 km or so one might get after the gas light comes on. Having heard the stories of running until it stops, pretty sure I'm not willing to test that thought!

I did inadvertently run it down to 0% last week once about a km before the Supercharger, but it wasn't on a single run as I'd had to top and charge a couple of times when towing so calculating the total available would have been challenging. Next time I'm doing a towing run I'll see if I can keep closer watch and try and get close to 0% when very near the Supercharger.

 

[_jmk]

Slightly OT, but things have changed in the new software version IMHO. Not only it charges way faster (seems to max out at 125kW instead of 100 before, 40kWh charge time dropped from 32min to 25min), the consumption seems lower as well. Driving the same roads as before, my consumption seems ~10% lower than ever before and the 'kWh used' discussed here goes tiny bit (1-2kWh) higher as well.

 

[NoBeard]

Slightly OT, but things have changed in the new software version IMHO. Not only it charges way faster (seems to max out at 125kW instead of 100 before, 40kWh charge time dropped from 32min to 25min), the consumption seems lower as well. Driving the same roads as before, my consumption seems ~10% lower than ever before and the 'kWh used' discussed here goes tiny bit (1-2kWh) higher as well.

I'd say that's right on topic. Interesting that it might give a tiny boost in available capacity. We have noticed the 125 kw charge rate making a great drop in the charge times when we just need that little boost to get to the home HPWC.

 

[gangzoom]

Finally had a chance to run the battery down to below 10% today.

Started the day with SOC at 74% and arrived at SC with 7%.

So 44.8kWh consumed over 67% = 67kWh usable at 100%, at 26,000 miles

Looking back the first long trip I did in our X when new using the same calculations I can see over 26K degradation is around about 1kWh, or below 2% at 26K!!!

64.3kWh consumed over 94% = 68kWh usable at 100% when at 2,251 miles.

I know people quote 72.5kWh usable when new for a 75kWh pack, but I've never ever been able to pull anything over to 70kWh from our X, maybe Tesla 'hides' 2kWh or so after reaching 0% but I have no interest in testing that theory.

Overall really really happy with how the battery is performing in our 75DX, people love to stress about drops in rated range, but from my experience if you treat the battery right - Don't charge to above 80% unless you need too, and avoid running below 10%, these battery packs are going to outlast the rest of the car .

 

[ajdelange]

It seems that what you are really interested in knowing is how much charge is available from the battery. In order to determine that you will have to look at a fair amount of data as individual are subject to quite a bit of variation. Driving data is not that useful because, as has been mentioned here several times, the power consumption during a drive depends a great deal on how you drive and the conditions you drive in. Charging is different. If you charge at home most of the time conditions are pretty much the same for each charge besides which the car measures the actual energy (integral of current times voltage) delivered to the battery irrespective of the source (SC, CHAdeMO, HPWC...) or the charger's (in the car) efficiency. Nevertheless there is variation so you must look at several measurements and average them. The table below summarizes 18 charges for my X 100D.

Looking at the first line as an example, the car reported that it added 11.27 kWhr which increased its rated range by 36.21 miles. The ratio of those two numbers is 3.21 miles per kWh. If the EPA rated range of the car is 295 miles then rated battery capacity must be 11.27*295/36.21 = 91.81 kWh. Now that's a rather low number (the lowest in the list) but note that other charges give estimates as high as 114.29 kWh. Why the estimates vary so much I do not know. Certainly there are some measurement errors, rounding errors... involved and I suspect sample time considerations may enter into it too but when all is said and done I would expect, or at least hope, that on average the car's algorithm is accurate. Thus the obvious thing to do is take the average. Doing that give the estimated usable rated capacity of my battery is 99.7 kWh. One sees various capacity numbers for the battery published with various figures given for how much of this is unusable as safety margin etc. The method of calculation described here is based on the reported kWh added, the rated miles added and the rated range of the car. Note also that these data yield an estimate of the rated Wh/mi of the car which is 337.2 ± 16.7 Wh/mi.

Now what the trip meters will show depends, as noted, on conditions and your driving habits. Over the 4000 miles since I've had the car I have realized 301 Wh/mi. Your mileage may vary.

 

[gangzoom]

Driving data is not that useful because, as has been mentioned here several times, the power consumption during a drive depends a great deal on how you drive and the conditions you drive in.

I've found driving data to be consistently be about 66kWh for our 75D X if your not going into the bottom 10%.

I mainly want to keep track of degredation which really does appear to be minimal!

 

[ajdelange]

I need to clarify. Driving data is not that useful for determining the available maximum battery capacity. It is extremely valuable for learning how you drive, how weather effects your car etc. With some experience you will know that one particular trip you make fairly frequently takes 10% more than your average energy consumption and another trip takes 20% less. It's also very helpful to know what your average is. As for keeping track of the battery degradation that is best done, as I indicated in my previous post, by tracking charges - not usage. Easiest way to do that is to use Teslafi or Stats to do what I did automatically for every charge. Both those programs display graphs showing battery degradation vs odometer miles (or km).

 

[pvandamcom]

This is a bit of an older thread, but i've been monitoring this as well (without tools...), just from the question how much kWh is available from 100% to almost 0% and excluding taking into consideration the charging losses. Those don't seem to be relevant in these calculation, nor does driving style seem to be relevant on how many kWh's you have available to drive, as original poster stated.

I've recently had a few continuous rides (with a few hours stop in the middle) of 390km, ending with 22km of range at 155Wh/km (the average of the "Since last charge" trip meter).
So the 390km @ 155Wh/km is 60,5 kWh, I estimated the 22km remaining @ 4,2 kWh (22 x my typical 194 Wh/km range).
This would bring my total drivable range to almost 66kWh. from the roughly 72kWh that should be available.

My assumption is that the 6 kWh "missing" is:
- partly battery degradation (90k kilometers),
- partly 0 is not entirely 0 (not sure I want to try..)
- partly some phantom drain during the stop