How many kWh does your battery actually have?

[Chaserr]

Gents, you just do not understand the tool you are using. Pack has the capacity you were promised, calculate it yourself. Set the % display, open the consumption tab. Now: (avg consumption * range remaining) / soc % in the form 0.5 for example (meaning 50% soc). The result is Watt hours in your pack.

The ‘used kWh’ display is just wrong. Forget it when it comes to these calculations.

On Batterygated cars this is not true. Tesla lowered volts which has a measurable kWh capacity decrease that limits you far below what was promised or ever tested by the EPA.

 

[_jal_]

Gents, you just do not understand the tool you are using. Pack has the capacity you were promised, calculate it yourself. Set the % display, open the consumption tab. Now: (avg consumption * range remaining) / soc % in the form 0.5 for example (meaning 50% soc). The result is Watt hours in your pack.

The ‘used kWh’ display is just wrong. Forget it when it comes to these calculations.

Do you know what the “used kWh” number is? I’m not being confrontational, I really am curious

 

[r1200gs4ok]

Do you know what the “used kWh” number is? I’m not being confrontational, I really am curious

so please tell us

 

[_jal_]

Gents, you just do not understand the tool you are using. Pack has the capacity you were promised, calculate it yourself. Set the % display, open the consumption tab. Now: (avg consumption * range remaining) / soc % in the form 0.5 for example (meaning 50% soc). The result is Watt hours in your pack.

The ‘used kWh’ display is just wrong. Forget it when it comes to these calculations.

I did this today in a normal day’s driving and got 95 kWh. Again, that seems about okay.

I’m wondering what the difference is between the displayed “used kWh” and the actual “used kWh” - inasmuch as I used 99% of them and that was 88 point whatever kWh. I’d imagine cabin overheat protection usage would contribute to the displayed number, but maybe not. So “phantom drain” isn’t included? Is “usage kWh” just power delivered to the drivetrain? Does anyone know?

 

[_jal_]

What is it you’re expecting to see?

A number closer to 100 kWh. I am not a hater. I’m an engineer who is just interested in where the difference between 102 kWh and 88 kWh goes. That’s a lot of kWh that *goes* somewhere.

And *edit* the only reason I’m citing 102 is that’s the battery capacity from Jason’s teardown of the physical pack

 

[GeorgeM]

Gents, you just do not understand the tool you are using. Pack has the capacity you were promised, calculate it yourself. Set the % display, open the consumption tab. Now: (avg consumption * range remaining) / soc % in the form 0.5 for example (meaning 50% soc). The result is Watt hours in your pack.

The ‘used kWh’ display is just wrong. Forget it when it comes to these calculations.

So that would say that I have a battery with 96 kWhs available. (241Wh/mi * 176 miles remaining)/.44 = 96.4 kWh. Quite reasonable for the available capacity. Now consider the Monroney sticker. Range is 348 miles and the car uses 32 kWh/100 miles, per the sticker. That calculates to a battery capacity of 111 kWh. Seem you can draw any conclusion you want about the battery and range depending on what measurement/reading you want to look at. None of this detracts from the car. Rated range/capacity/efficiency aside it always gets me where I need to go with a grin on my face.

 

[_jal_]

So that would say that I have a battery with 96 kWhs available. (241Wh/mi * 176 miles remaining)/.44 = 96.4 kWh. Quite reasonable for the available capacity. Now consider the Monroney sticker. Range is 348 miles and the car uses 32 kWh/100 miles, per the sticker. That calculates to a battery capacity of 111 kWh. Seem you can draw any conclusion you want about the battery and range depending on what measurement/reading you want to look at. None of this detracts from the car. Rated range/capacity/efficiency aside it always gets me where I need to go with a grin on my face.

It would be nice to know what goes into effective range. So driving through snow is definitely a negative. Always having the heat on blazing is a negative. Etc. But it’s weird to argue “oh, it’s not the consumption per mile that’s changing, it’s the capacity of the battery that’s changing.” There are some activities that detract from range not included in the “used kWh.” What’s the math?

 

[GeorgeM]

What’s the math?

That's like asking what the formula to Coke is. Never going to be public knowledge.

 

[_jal_]

What’s the math?

That's like asking what the formula to Coke is. Never going to be public knowledge.

I honestly just wondered how I can burn a whole battery in a day and only get credit for 88 kWh.

 

[ucmndd]

I honestly just wondered how I can burn a whole battery in a day and only get credit for 88 kWh.

You’re putting a lot of faith in that “since last charge” number being accurate, despite not a lot of evidence to suggest it is. In my experience it’s only a little bit better than an educated guess.

 

[_jal_]

You’re putting a lot of faith in that “since last charge” number being accurate, despite not a lot of evidence to suggest it is. In my experience it’s only a little bit better than an educated guess.

Yeah, I guess so. I would have thought that number would have been easy to get at, but if isn’t accurate then that’s that.

 

[ran349]

Yeah, I guess so. I would have thought that number would have been easy to get at, but if isn’t accurate then that’s that.

I think the number can be pretty accurate, but I think the bigger issue is that your expectations are too high for what you think the value should be.
I showed you a Scan My Tesla readout that showed 92.8 kWh usable, from a basically new car. So your 88 kWh is just about 5% less than that. Now, you said you had some degradation. How much degradation? How many rated miles new vs. how many now?

Also, the "since last charge" will not include any energy lost when you are not moving. You didn't say if you stopped for any significant amount of time during your trips. But that will cause the number to read lower as well.

Don't put much stock in Jason Hughes 102 kWh number. It doesn't reflect the buffer(s) that the car uses and are blocked from you to access.

I think your 88 kWh number seems fairly normal, given the circumstances you have provided.

 

[_jmk]

You’re putting a lot of faith in that “since last charge” number being accurate, despite not a lot of evidence to suggest it is. In my experience it’s only a little bit better than an educated guess.

It probably only counts the energy that moves the car. Cooling, heating, etc. are excluded.

 

[ran349]

It probably only counts the energy that moves the car. Cooling, heating, etc. are excluded.

Incorrect. It includes all of the above, as long as the car is moving, but not when it stops.

 

[_jmk]

So that would say that I have a battery with 96 kWhs available. (241Wh/mi * 176 miles remaining)/.44 = 96.4 kWh. Quite reasonable for the available capacity. Now consider the Monroney sticker. Range is 348 miles and the car uses 32 kWh/100 miles, per the sticker. That calculates to a battery capacity of 111 kWh. Seem you can draw any conclusion you want about the battery and range depending on what measurement/reading you want to look at. None of this detracts from the car. Rated range/capacity/efficiency aside it always gets me where I need to go with a grin on my face.

That sticker is nonsense as it’s based on unrealistically low consumption and/or ’test cycle optimization’ - but the 96kWh of usable energy is relatively accurate. Note that the percent is rounded, so you need more than one reading for more accurate results. That is the amount of energy the bms thinks you can use. Buffers are on top of this, so the pack is likely a bit bigger than 100kWh total.

 

[_jmk]

Incorrect. It includes all of the above, as long as the car is moving, but not when it stops.

Incorrect. It includes all of the above, as long as the car is moving, but not when it stops.

Yes, it stops updating when the car stops. But while it moves, it seems to behave that way. I don’t claim to know what it’s excluding, but certainly something, so this has been my guess. What’s yours?

 

[ran349]

That sticker is nonsense as it’s based on unrealistically low consumption and/or ’test cycle optimization’ - but the 96kWh of usable energy is relatively accurate. Note that the percent is rounded, so you need more than one reading for more accurate results. That is the amount of energy the bms thinks you can use. Buffers are on top of this, so the pack is likely a bit bigger than 100kWh total.

The sticker number is not nonsense. It is an EPA number that includes charging losses, so that is why it is so high.

 

[ran349]

Yes, it stops updating when the car stops. But while it moves, it seems to behave that way. I don’t claim to know what it’s excluding, but certainly something, so this has been my guess. What’s yours?

I don't believe it does exclude energy when you are driving.That hasn't been my experience. When I drive and turn on heat or air, my Wh/mi goes up accordingly.

My displayed usage also tracks closely with the BMS provided Scan My Tesla usable number when I do a continuous drive, which is another indicator that it is reasonably accurate.

 

[CB198]

Real capacity vs CANBUS capacity. I have a usable between 68 - 70 kWh, but I'm getting around 63 - 64 kWh max into the car from dead to 100%. That's 7 kWh degradation (CANBUS) and 13 kWh based kWh into the wall connector. Working with 10 - 17% battery degradation.

That's difficult to refute. Especially that the car had a usable capacity of 77 kWh new. The service center has a battery discharger. There are references to it in the Service Manual you can torrent online. Why wouldn't that measure the power after a full discharge?

If they claim the battery has no degradation, make them put their money where their mouth is and measure the discharge. It's a hard sell because the labor involved. But If you get a Sense learning power meter, you can directly measure how much power is being put into 2nd generation onboard chargers. It hasn't picked up what a Model 3 charges with yet but I'm hoping that it's a matter of time.