Model 3 Battery Capacity

[Wooloomooloo]

I think what I'd really like to know is what wh/mi I need to hit to get the rated range for better planning. If my maths is correct (it probably isn't) assuming a 75kw/h pack I'd need to hit around 242 wh/mi to get the 'rated' range (i.e. the full 310 actual miles from a full batter).

If it's really a 73 kw/h pack, then I have to hit 235 wh/mi to get that range.

In the first week with my P+ I was getting around 290 wh/mi, but I was giving it some right foot love during that time. Yesterday I did a 114 mile trip from Brooklyn to Ossining in Westchester plus some driving around the river towns, I got 229 wh/mi driving pretty gently - speeds only really up to 55-60mph on the highways but mostly 20 - 40mph in the towns. At one point I was monitoring the rated range dropped 70 miles for 68 real miles - overall I got 114 real miles for 120 rated miles even with my average 229 wh/mi. This was over the course of a 10 hour day - I didn't use any cabin heat or A/C during this time.

This coming Friday I am doing a 440 mile trip to Akron, OH (and return leg on Sunday) which will be a good 400 miles of solid highway driving - n the way there I'll be seeing what I can squeeze out of this puppy in terms of range.

 

[NewTMSMan]

I think what I'd really like to know is what wh/mi I need to hit to get the rated range for better planning. If my maths is correct (it probably isn't) assuming a 75kw/h pack I'd need to hit around 242 wh/mi to get the 'rated' range (i.e. the full 310 actual miles from a full batter).

If it's really a 73 kw/h pack, then I have to hit 235 wh/mi to get that range.

In the first week with my P+ I was getting around 290 wh/mi, but I was giving it some right foot love during that time. Yesterday I did a 114 mile trip from Brooklyn to Ossining in Westchester plus some driving around the river towns, I got 229 wh/mi driving pretty gently - speeds only really up to 55-60mph on the highways but mostly 20 - 40mph in the towns. At one point I was monitoring the rated range dropped 70 miles for 68 real miles - overall I got 114 real miles for 120 rated miles even with my average 229 wh/mi. This was over the course of a 10 hour day - I didn't use any cabin heat or A/C during this time.

This coming Friday I am doing a 440 mile trip to Akron, OH (and return leg on Sunday) which will be a good 400 miles of solid highway driving - n the way there I'll be seeing what I can squeeze out of this puppy in terms of range.

If you have V9 you should see for the car what WHr/mile is needed to get 310 miles of range in the Energy Monitor. You may need to do what I did and take a picture and then measure and extrapolate to get the right number. I got 254 WHr/mile for our Performance Model 3 from that graph. Using this backward this means:

Available Battery Capacity = 310 x 254 = 78.7 kWHr

Up until I had access to V9 and the Energy Monitor screen, which seems to show 254 WHr/mile I was assuming the same thing you notes, which was if the battery is 75 kWhr and the range is 310 miles then the Rated Average WHr/mile is 242 WHr/mile.

 

[Wooloomooloo]

If you have V9 you should see for the car what WHr/mile is needed to get 310 miles of range in the Energy Monitor. You may need to do what I did and take a picture and then measure and extrapolate to get the right number. I got 254 WHr/mile for our Performance Model 3 from that graph. Using this backward this means:

Available Battery Capacity = 310 x 254 = 78.7 kWHr

Up until I had access to V9 and the Energy Monitor screen, which seems to show 254 WHr/mile I was assuming the same thing you notes, which was if the battery is 75 kWhr and the range is 310 miles then the Rated Average WHr/mile is 242 WHr/mile.

I don't have V9 yet, apparently for my car it will be closer to the end of the month according to my service rep, but if I get it before the road trip I'll do that.

The 78.7kWHr seems about right given the EPA originally said the batter was 80.5 and of course Lithium batteries keep a reserve of about 5% when 'fully discharged' (yes the irony is that they never truly become fully discharged at all).

But here's something else. The EPA rating for the RWD Model 3 is 126MPGe and for the Performance it's 116MPGe. Some quick maths says that's a 8.6% difference (that is the RWD is 8.6% more efficient than the P+) so to get the same 310 miles rated range from the same agency, you'd expect the difference in battery capacity to be the same.

The difference between a 78kWHr pack and 73, is only 3.5% - so there are clearly other factors at play, or these numbers are wrong.

 

[JeffK]

these numbers are wrong.

exactly

 

[Wooloomooloo]

exactly

Nice.

I think we have exactly the same car BTW - you have good taste (my Avatar is my car at pick up).

 

[JeffK]

Nice.

I think we have exactly the same car BTW - you have good taste (my Avatar is my car at pick up).

We do! I modified Franz's drawing to add the red brake calipers and correct wheels.

 

[NewTMSMan]

I don't have V9 yet, apparently for my car it will be closer to the end of the month according to my service rep, but if I get it before the road trip I'll do that.

The 78.7kWHr seems about right given the EPA originally said the batter was 80.5 and of course Lithium batteries keep a reserve of about 5% when 'fully discharged' (yes the irony is that they never truly become fully discharged at all).

But here's something else. The EPA rating for the RWD Model 3 is 126MPGe and for the Performance it's 116MPGe. Some quick maths says that's a 8.6% difference (that is the RWD is 8.6% more efficient than the P+) so to get the same 310 miles rated range from the same agency, you'd expect the difference in battery capacity to be the same.

The difference between a 78kWHr pack and 73, is only 3.5% - so there are clearly other factors at play, or these numbers are wrong.

Actually they are rated 130 MPGe and 118 MPGe respectively for 2018 - Gas Mileage of 2018 Tesla Model 3

This difference is slightly over 9%, and while the difference is different in magnitude, how could the car have the same range for both models from the same battery, but different MPGe?

You cannot really directly compare the EPA MPGe because the basis is different than the Rated Range and Rated Efficiency. In addition to the MPGe not being allowed to be modified, while the Rated Range can be adjusted (and has by Tesla for the Model S), the EPA MPGe basis is as follows:

MPGe = (0.7*(Charging Efficiency)* 33.7kWh/gallon*1000)/(0.55*City Wh/mi + 0.45* Highway Wh/mi)

So if you punch the numbers in from the EPA reference for the RWD Model 3 in my original post you will find:

City Efficiency = 172 Whr/mile
Highway Efficiency = 158 WHr/mile
Charge Efficiency = 91.5%

MPGe = (0.7*0.915*33.7*1000)/(0.55*172+0.45*158) = 130 MPGe

Or conversely if we work the equation backward to calculate the Average WHr/mile based on MPGe you would get:

Average WHr/mile = 33.7*1000/130 = 259.23 WHr/mile

but note this includes the charge efficiency as well as the 0.7 adjustment factor (because only 2 tests are used instead of the 5 normally required) used by the EPA. If you believe that the 0.7 factor appropriately creates the correct adjustment for a full test cycle then you would only correct for charge efficiency to arrive at the actual WHr/mile:

Average WHr/mile = 259.23*0.915 = 237 WHr/mile - Strangely Exactly what I measured from the graph for the RWD Model 3

Battery Available = 237 * 310 = 73,470 WHr

Unfortunately I do not have the full numbers for the Model 3 Performance, but if we assume similar factors:

MPGe = 118
Average WHr / Mile = 33.7*1000/118 * 0.915 = 261 WHr/mile - Not exactly what I measured at 254 WHr/mile, but still different than the RWD Average (121 MPGe would roughly be the equivalent of 254 Whr/mile).

Battery Available = 310*261 = 80,910 WHr

Now I mentioned MPGe and Rated Range are not directly comparable and that is because the MPGe uses the above formulas and EPA City and Highway Dyno cycles and the EPA Rated Range is based on a single EPA City-Highway cycle test that is run continuously until the battery dies and then the EPA typically applies a 90% factor to that result. As noted and is the case with Tesla the manufacturer can request differences in this and in the case of the Model 3 all have been set at 310 miles.

 

[Wooloomooloo]

Actually they are rated 130 MPGe and 118 MPGe respectively for 2018 - Gas Mileage of 2018 Tesla Model 3

I didn't realize the RWD had moved to 130 MPGe, but the Performance is 116 not 118 MPGe it says so on my sticker (which is 10 days old) and also on the website you linked to. I thought you'd made a typo, but you based your calculations on this number as well.

Regardless I understand the point you're making and I agree with your equations - I do think it's likely the Performance has access to a slightly larger pack (whether that's hardware or managed by software) but that the RWD is rated very conservatively (which is why it's so easy to beat the rated range). So far I have not managed to do better than the rated range, but if I ever do, I'll post the results here!

I'll go back to my original point which is that really what would be awesome is knowing exactly what WHr/Mi I need to hit to get to a destination with a specific charge, so I can better manage speed, heating and other things.

 

[SageBrush]

Up until I had access to V9 and the Energy Monitor screen, which seems to show 254 WHr/mile I was assuming the same thing you notes, which was if the battery is 75 kWhr and the range is 310 miles then the Rated Average WHr/mile is 242 WHr/mile.

I'm not sure if the Tesla 'rated mile' Wh/mile included charging losses

For fun, lets start with the EPA combined MPGe of 130 which is 33700 Wh/130 mile = 260 Wh mile
That number includes charging losses that are about 12.5%
To arrive at battery to wheels we take 260*.875 = 227 Wh/mile

The next step, of calculating battery capacity is tricky because Tesla decided to publish a range less than the actual test result Actual range was 334 miles, so battery capacity is 334*0.227 = 75.8 kWh

 

[lolder]

All the cars have the same size battery variously measured at 77.5 kwhr. Even that is at a given rate of discharge. If you drive faster you use more energy/mile AND you get less energy out of the battery. That's the only definitive statement you can make about range. The cars energy displays are all algorithms that try to inform you about your energy status and when you drive with significantly different styles only become accurate when the battery approaches zero. The new energy display will give you a good idea of how fast you can drive which is the biggest variable. Gas cars are the same. I've heard the 600 hp muscle cars at full throttle run out of gas in about 1/2 hour.

 

[NewTMSMan]

View attachment 344190

I didn't realize the RWD had moved to 130 MPGe, but the Performance is 116 not 118 MPGe it says so on my sticker (which is 10 days old) and also on the website you linked to. I thought you'd made a typo, but you based your calculations on this number as well.

Regardless I understand the point you're making and I agree with your equations - I do think it's likely the Performance has access to a slightly larger pack (whether that's hardware or managed by software) but that the RWD is rated very conservatively (which is why it's so easy to beat the rated range). So far I have not managed to do better than the rated range, but if I ever do, I'll post the results here!

I'll go back to my original point which is that really what would be awesome is knowing exactly what WHr/Mi I need to hit to get to a destination with a specific charge, so I can better manage speed, heating and other things.

You are right I used the incorrect number. Should have been 116 MPGe.

Getting colder here now so no chance I get anywhere near the efficiency to hit 310 miles in our P with 20” wheels. This weekend did a long trip out to LI and back on autopilot running at 65-75 MPH and only averaged around 310 Whr/mile for the trip.

 

[NewTMSMan]

I'm not sure if the Tesla 'rated mile' Wh/mile included charging losses

For fun, lets start with the EPA combined MPGe of 130 which is 33700 Wh/130 mile = 260 Wh mile
That number includes charging losses that are about 12.5%
To arrive at battery to wheels we take 260*.875 = 227 Wh/mile

The next step, of calculating battery capacity is tricky because Tesla decided to publish a range less than the actual test result Actual range was 334 miles, so battery capacity is 334*0.227 = 75.8 kWh

Already have the math for all of that in my prior posts and EPA charge efficiency seems to be 91.5% based on their data.

 

[clostridium]

Only 66 kWHr with 110 WHr/mile and 606 miles.

That is why I am not using their displayed actual usage data and am using their provided Rated data only.

Now the issue with my calculations may be that the Rated Efficiency is not being displayed properly in the Energy Monitor but, I have additional data from Remote S App (cannot share publicly as it is not for my cars) that shows RWD with 72 kWh battery capacity compared to it showing 75 kWhr capacity for my P. Now I only have that data for 1 car and that individual car may have battery issues so would not rely on this.

The calculations I provided are simple and based on Telsa data. Where in the calculations or the data I am using is there an issue that would point to me being wrong here?

I wouldn't depend upon Remote S - in my Model 3 it has shown anywhere from 62-83 kWh as my battery capacity. It usually sits around 75-77 though. Which is probably about right.