Vampire Drain? Simple way of checking it ...

[TomLee]

That is correct for the SR+.

For the “out” kWh, it is about 5% smaller.

For example, if you drive and use 20kWh on the trip meter, you will find that to recharge to your original miles, you will need to add about 21kWh. (5% difference).

In other words, it is about 209Wh per rated mile for consumption for the SR+ (I have no way to measure this myself on an SR+, so I do not know the actual exact value. I can only do that test with the AWD.

While I don’t have a dedicate meter at home, I have to rely on some kind of readings. All I have now is the screen display and the Stats app for now. So please tell me in your example, where can I find those 20kWh, 21kWh numbers? I assume 20kWh from the screen “kWh Used”, where is that 21kWh? I assume this is not “kWh Added” on the screen, otherwise the charging loss part is already been taken care of. Thoughts?

 

[AlanSubie4Life]

I assume this is not “kWh Added” on the screen, otherwise the charging loss part is already been taken care of. Thoughts?

Yes the 21kWh would be the kWh added.
The kWh added is “post” all charging losses and represents (my opinion) the available energy added to the battery. If you had a wall meter it would be another ~10% higher than that (exact amount depends on your charging setup efficiency).

In the Stats app you can switch between miles added and kWh added and you’ll see it is always a 245Wh/rmi relationship (or 219Wh/rmi for you).

 

[TomLee]

If you add ~10.5 kWh to the battery (according to the charge screen) and then immediately use all of that energy, the trip meter will show ~10kWh used. This 5% loss is automatic. Nothing to do with vampire drain, just how the car works.
It will then take you another 10.5kWh (according to the charge screen) to get you back to where you started.

Put another way, trip meter counts koWh. But charge screen shows you kiWh.

If you want to convert trip meter koWh to charge screen units you have to multiply by ~1.05.

This is new to me. So basically in my OP, 27kWh added only reflect to 25.7kWh used. Therefore, the loss was 25.7 - 21 = 4.7 kWh! Interesting.

 

[AlanSubie4Life]

This is new to me. So basically in my OP, 27kWh added only reflect to 25.7kWh used. Therefore, the loss was 25.7 - 21 = 4.7 kWh! Interesting.

Yes. That is approximately correct. Of course, you may want to actually scale up that difference by 5%. Depends on what “type” of kWh you want to quote your vampire losses in.

If you were using a Supercharger to replace those miles, you’d need to pay for ~1.05* 4.7kWh. This is all very approximate as I am being careless about 0.95 being equal to 1/1.05. But you get the idea.

 

[TomLee]

How did you guys find out the trip meter constant is different from the charging meter constant? Smart! I didn’t even dive into the trip meter part yet. But I guess concept wise, I’m not too far off!

 

[AlanSubie4Life]

How did you guys find out the trip meter constant is different from the charging meter constant? Smart! I didn’t even dive into the trip meter part yet.

For me, just observation. @darth_vad3r plays with the API and has even more visibility.

I need to dig up a couple sample pictures where you can see the calculation - will post in a bit.

 

[TomLee]

For me, just observation. @darth_vad3r plays with the API and has even more visibility.

I need to dig up a couple sample pictures where you can see the calculation - will post in a bit.

Not in a hurry, I may need to have some sleep now. Have a good trip!

 

[AlanSubie4Life]

Not in a hurry, I may need to have some sleep now. Have a good trip!

Oh, I took the trip already!

Here is my starting point this morning (299 miles - could not get the slider to 100%, so had to settle for 98% - I had no cellular access so the Stats app and Tesla app were both useless for setting 100% charge..)

And here is the end at the LINQ 250kW Supercharger, about 5 hours later.

You can see I went 282.3 miles and used 225Wh/mi. (in a Performance!!! ...It was downhill a LOT - North Rim Grand Canyon to Vegas)
That used 299-21 = 278 rated miles.

So, 282.3mi*225Wh/mi / (278 rmi) = 228.5Wh/rmi

Note it is not 230Wh/mi because I did actually sit briefly at Point Imperial with the door open on this stretch - so I had about 30 minutes of vampire drain. Normally the value is 230Wh/rmi (I have lots of other segments I can look at).

Here is the Supercharger data (ignore the trip meter data - I was resetting it a few times to monitor my consumption to make sure I would make it to Vegas...):

I added (in 21 minutes!!!) 202 miles - which was 49kWh (242Wh/rmi - this is just rounding error due to the % and number of rated miles resolution...there are only two significant digits here...the actual value is 245Wh/rmi)

Kind of an aside (for this conversation): Note the key implication of the above: to get a mile traveled for mile of range used, you need to get 230Wh/mi in an AWD. Not 245Wh/mi. When using trip meter numbers.

 

[TimothyHW3]

BTW, if I compute Wh added over the km added, I get a constant of 136Wh/km (219Wh/mile) which I believe is what Tesla uses to convert Wh into range.

I’d like to be educated. Seriously, thanks!

I am not sure you do, because you quickly pressed disagree on my post without understanding it.

If you go back to the post, I actually told you that you don't need to calculate the constant - it is shown to you in plain sight in your Energy diagramm inside the car. It should be more close to 142, but I don't have an SR+ to check the screen.

And as @ewoodrick, me or anyone else for that matter explains, the only way for you to measure the drain during a stay is to measure the loss of KMs. There is nothing complicated or wrong about it. The KMs on your screen are just a different representation of kWh and I explained how did is done with the constant. So whenever you see a km loss, this is just a UI representation of (let's assume 54kWh total and 142Wh/km) roughly 142Wh being lost.

You misunderstood that as "driving conditions" - no, they are a constant that is being used to translate kWh into KMs and they are the same every time you leave the car. The constant also never changes during driving either, but if you drive above it you will get less range, if you drive below it more(roughly speaking, because I don't want to go into details how Tesla is lying you about rated range

And I never said I take "driving conditions" into vampire drain - you do.

No, vampire drain does not happen over a day or two - it happens the minute you walk out of the car and is dependent on the electronics that still continue to run(sentry mode, wifi updates, cameras) etc. If you read my thread on vampire drain, you will see what affects that.

Hope this helps to unconfuse you.

 

[darth_vad3r]

If you go back to the post, I actually told you that you don't need to calculate the constant - it is shown to you in plain sight in your Energy diagramm inside the car. It should be more close to 142, but I don't have an SR+ to check the screen..

Are you talking about the line on the chart? That’s not at 142, it’s between 139 and 140, and it is different than the constant used by the car to map kW to charge ‘speed’ and to map kWh of energy added to km of range added.

That constant is 219 Wh/mi for SR+ (136.08 Wh/km) which is lower than the line on the chart (~139.5).

That line on the chart is pretty much useless.

What the chart does tell you is the constant. If you take the 2 numbers from the chart (Wh/km and projected km range) and multiply them to get a Wh energy number, then divide that by the km range on your battery gauge, you’ll get 136.08 (if you do it enough times that should be your average anyways, it’s going to vary due to rounding errors).

 

[TimothyHW3]

Are you talking about the line on the chart? That’s not at 142, it’s between 139 and 140, and it is different than the constant used by the car to map kW to charge ‘speed’ and to map kWh of energy added to km of range added.

That constant is 219 Wh/mi for SR+ (136.08 Wh/km) which is lower than the line on the chart (~139.5).

That line on the chart is pretty much useless.
.

Like I said, I don't own an SR+ and only based it on the assumption of 54kWh and around 381km shown as I was told. Which is pretty close. If you drive with the same consumption as the "line", you will see the exact 3 digit number.

I have an AWD and can tell you about it, the SR+ was actually a pretty close estimation.

And no, this line is not useless, because this is what Tesla is using to calculate your rated miles(the number you get when you charge the car or during battery drain while stationary) - kWh(nominal full with buffer) divided by typical consumption constant in the pack gives you the rated miles on display. So whenever your car is stationary and it loses 140Wh, it deducts roughly 1km from the screen

What @Alan is trying to explain is that if you drive around that line you will never reach the rated miles, but this is not, because it is "useless", but due to the way Tesla calculates the rated miles.
Iexplained it in detail in the other thread so without much repeating myself - the rated miles use the constant over the full kWh capacity of the battery, but the 100% is not calculating the buffer, this is why if you drive at rated miles you will get 96% of the rated miles due to the buffer being 4% roughly.

 

[TomLee]

I am not sure you do, because you quickly pressed disagree on my post without understanding it.

If you go back to the post, I actually told you that you don't need to calculate the constant - it is shown to you in plain sight in your Energy diagramm inside the car. It should be more close to 142, but I don't have an SR+ to check the screen.

And as @ewoodrick, me or anyone else for that matter explains, the only way for you to measure the drain during a stay is to measure the loss of KMs. There is nothing complicated or wrong about it. The KMs on your screen are just a different representation of kWh and I explained how did is done with the constant. So whenever you see a km loss, this is just a UI representation of (let's assume 54kWh total and 142Wh/km) roughly 142Wh being lost.

You misunderstood that as "driving conditions" - no, they are a constant that is being used to translate kWh into KMs and they are the same every time you leave the car. The constant also never changes during driving either, but if you drive above it you will get less range, if you drive below it more(roughly speaking, because I don't want to go into details how Tesla is lying you about rated range

And I never said I take "driving conditions" into vampire drain - you do.

No, vampire drain does not happen over a day or two - it happens the minute you walk out of the car and is dependent on the electronics that still continue to run(sentry mode, wifi updates, cameras) etc. If you read my thread on vampire drain, you will see what affects that.

Hope this helps to unconfuse you.

I’m sorry to make you feel insulted. I'm sure I didn't understand the whole picture of your post because I don't even know which post were you talking about 'cause you never mentioned it in my post. As I stated, I was on the same boat trying to represent the loss as kms and I'm not saying "your" method is wrong. I'm just trying to use a simple method to represent something in some numbers.

 

[TomLee]

I am not sure you do, because you quickly pressed disagree on my post without understanding it.

Please educate me with your post, where was it?

If you go back to the post, I actually told you that you don't need to calculate the constant - it is shown to you in plain sight in your Energy diagramm inside the car. It should be more close to 142, but I don't have an SR+ to check the screen.

I never mentioned the constant was used in my simplified method. Those constants was for making sense other things and cross referencing numbers.

And as @ewoodrick, me or anyone else for that matter explains, the only way for you to measure the drain during a stay is to measure the loss of KMs. There is nothing complicated or wrong about it. The KMs on your screen are just a different representation of kWh and I explained how did is done with the constant. So whenever you see a km loss, this is just a UI representation of (let's assume 54kWh total and 142Wh/km) roughly 142Wh being lost.

I never disagreed with you guys about it, did I?

You misunderstood that as "driving conditions" - no, they are a constant that is being used to translate kWh into KMs and they are the same every time you leave the car. The constant also never changes during driving either, but if you drive above it you will get less range, if you drive below it more(roughly speaking, because I don't want to go into details how Tesla is lying you about rated range

And I never said I take "driving conditions" into vampire drain - you do.

All I'm saying is that the range on the screen is only a guesstimated number. With the same level of of SoC, it may represent different range on your screen. If you agree with me, please read on. With two very different drive, the estimated ranges shown on the screen is different. When you write down that two sets of numbers (delta from set the car to park until next time you get in the car), those two sets meant different already. Say for example, 1st day you drove all the way uphill and park, recorded the numbers, 2nd day drove all the way downhill and park, recorded numbers, 3rd day record your numbers before you drive. Now you have two sets of delta between 1st and 2nd day, 2nd day and 3rd day. Even if they are the same 1km number, those 1km were different. Drain between 1st and 2nd day was higher than 2nd to 3rd day. This is the whole concept why I felt less accurate to record drain in kms. As I'm pretty new in the community, I believe I have a lot of things to learn and I'm willing to do so. But please enlight me instead of blame me, Thanks!

No, vampire drain does not happen over a day or two - it happens the minute you walk out of the car and is dependent on the electronics that still continue to run(sentry mode, wifi updates, cameras) etc. If you read my thread on vampire drain, you will see what affects that.

Hope this helps to unconfuse you.

Totally agree, vampire drain happens the minute you set your car in park.

 

[TomLee]

Add a little bit more to the screen I posted. The battery capacity is around 52.4kWh according to my calculation. I have used 21kWh and drove 140.4km. Therefore, I should have 52.4 - 21 = 31.4 kWh left and range remained should show 140.4km x 31.4/21 = 210km (assuming the computer used the same Wh/km to calculate the range) before charging. This is obviously not the case because we all know vampire drain is in the play. The range before charging was 103km on the display. Assuming 27kWh x 0.95 (factor suggested by @darth_vad3r) was accounted for the calculation of the range, we should have 52.4 - 27x0.95 = 26.75kWh left before charging. Estimated range before charging should see 140.4 x 26.75/21 = 178.33km. This is still way bigger than the 103km on display. So I back calculated the kWh/km used to calculate the left range: 26.75kWh/103km = 260Wh/km (418Wh/mile). Unfortunately, this number is all over the place fro 160Wh/km to 260Wh/km according to my limited recording, which also means the "left range" is not calculated using a constant. Is there anything wrong with my calculation? Added kWh/km is very consistent at 136Wh/km thou.

 

[TomLee]

So, 282.3mi*225Wh/mi / (278 rmi) = 228.5Wh/rmi

Note it is not 230Wh/mi because I did actually sit briefly at Point Imperial with the door open on this stretch - so I had about 30 minutes of vampire drain. Normally the value is 230Wh/rmi (I have lots of other segments I can look at).

Kind of an aside (for this conversation): Note the key implication of the above: to get a mile traveled for mile of range used, you need to get 230Wh/mi in an AWD. Not 245Wh/mi. When using trip meter numbers.

Now I get what you are talking about the 5% difference. Anyway, looks like this constant can be calculated for a long trip (for accuracy) right after charging to avoid other factors into play. I have never recorded that way, therefore, never come across that constant number.

Thanks!