2020, 2019, 2018 Model 3 Battery Capacities & Charging Constants

[Wreckless316]

No. I've also done this wrong in the past, but for vampire drain, you're looking at displayed rated miles.

It's ~200Wh per displayed rated mile, as mentioned above, so you should use that value. In fact, for any calculation, use the value for Wh per displayed rated mile (not the charging constant). As I said above, it may well be easiest to just ignore the charging constant. It's kind of unnecessary noise, though it is directly related to the per rated mile/discharge constant...and it shows up on the charging screen indirectly...so we carry it around and track it...

So, If you lost 3.5kWh of energy (untracked as mentioned above): that is 17.5 rated miles in 6 days, 2.92 miles per day.

The miles on your screen each are worth ~200Wh from your battery. It's that simple. If you drive up 1000 feet, that's about 1.4kWh potential eneergy in addition to the driving. So that's going to require at least 7 rated miles (slightly more due to drivetrain inefficiency) more than driving the same distance on the flat.

Yes. It is useful for calculating your full remaining battery capacity, which includes the buffer, at 100%, and is predictive of what the CAN bus readback would tell you.

Or you can just use the discharge constant, multiply by your rated miles at 100%, and divide by 0.955. It will give you the same value.

excellent thanks for answering all my silly questions. Now for the final dagger.

I know that 2-3 miles per day vampire is low. But you mentioned in another thread it’s possibly to get it down to 1 mile per day. What sort of outside the box things can I do to get it that low? It’s somewhat important as I don’t have a home charger and need t maximize efficiency

 

[AlanSubie4Life]

excellent thanks for answering all my silly questions. Now for the final dagger.

I know that 2-3 miles per day vampire is low. But you mentioned in another thread it’s possibly to get it down to 1 mile per day. What sort of outside the box things can I do to get it that low? It’s somewhat important as I don’t have a home charger and need t maximize efficiency

I answered in the other thread, to keep this one on topic. Keep in mind that your actual vampire is probably lower than the 3 rated miles per day, because ANY time you spend sitting in the car in park, etc., will add a bit of additional drain. You already seem to be doing pretty well - you might be closer to 2 to 2.5 miles per day, and in an 2020 SR+ that is really good since those miles don't have a bunch of energy in them compared to an AWD Performance.

 

[Supermanwoot]

I'm pretty sure my 2020 sr+ has a usable (100% to 0%) battery of 47.5 kwh.

Did tesla fudge the numbers for the epa by unlocking part of the pack?

 

[AlanSubie4Life]

I'm pretty sure my 2020 sr+ has a usable (100% to 0%) battery of 47.5 kwh.

Did tesla fudge the numbers for the epa by unlocking part of the pack?

No. It is probably just the buffer which cannot be counted on in most situations. What is your rated miles at 100%?

If this projection of yours is accurate and based on the trip meter (can you provide the details?), the answer should be:

47.5kWh/197Wh (trip)/rmi = 241rmi

And your actual full capacity as per ScanMyTesla would be about:

47.5kWh/0.98/0.955 = 50.75kWh

(50.75kWh/210Wh/rmiEPA) = 241rmiEPA

It is pretty easy to miss some energy if you are using % and not careful, so I suspect the actual answer is a bit higher...

 

[ElectricIAC]

At least we know Tesla’s “keepin’ it 100” on the overpromise and underdeliver front.. You see the new numbers on S/X LR?

 

[Wreckless316]

I answered in the other thread, to keep this one on topic. Keep in mind that your actual vampire is probably lower than the 3 rated miles per day, because ANY time you spend sitting in the car in park, etc., will add a bit of additional drain. You already seem to be doing pretty well - you might be closer to 2 to 2.5 miles per day, and in an 2020 SR+ that is really good since those miles don't have a bunch of energy in them compared to an AWD Performance.

How about this one. When I do the math seems like excessive vampire drain. Can you outline the math with this scenario?

 

[AlanSubie4Life]

How about this one. When I do the math seems like excessive vampire drain. Can you outline the math with this scenario?

How long a period? You should really log (picture as above) the beginning and end of each drive over a given period if you want to track down vampire losses.

Also what did you start with? 233 rated miles?

If so, I get 42.8kWh used on trip meter, out of 229rmi*197Wh (trip)/rmi = 45.1kWh actually used.

So that’s 2.3kWh lost. I would not call that excessive over 3-4 days.

 

[Wreckless316]

How long a period? You should really log (picture as above) the beginning and end of each drive over a given period if you want to track down vampire losses.

Also what did you start with? 233 rated miles?

If so, I get 42.8kWh used on trip meter, out of 229rmi*197Wh (trip)/rmi = 45.1kWh actually used.

So that’s 2.3kWh lost. I would not call that excessive over 3-4 days.

232 to start with at 95%

51.5 (.955) (.98)(.95)= 45.79 used

235.2 (182)= 42.8 trip meter used

About 3kwh wasted using your other formula ?

 

[AlanSubie4Life]

51.5 (.955) (.98)(.95)= 45.79 used

Should not use this here because you know how many rated miles you use. As I said, unnecessarily complex.

Also made a mistake - you only used 93%.

51.5*0.955*0.98*0.93 = 44.8kWh.

Easier to just do (232rmi-4rmi)*197Wh/rmi = 44.9kWh

 

[jdcollins5]

@AlanSubie4Life

Here are two segments of a trip I took a couple of weeks ago. First trip was cold and rainy. Return trip was 60-70’s.

Wilmington to Greensboro, NC:
-Weather: 45->35->45 temps, overcast->rain->wintry mix->overcast
-Elevation change: +800 feet
-Odometer miles = 222
-Range miles = 274 (306@99% - 32@10%)
-Trip Wh/rm = 272
-Trip kWH = 60
-SC kWH = 64

Winston-Salem to Wilmington:
-Weather: Sunny and 68->72
-Elevation change = -800 feet
-Odometer miles = 255
-Range miles = 253 (303@98% - 50@16%)
-Trip Wh/rm = 224
-Trip kWH = 57
-Home Charger kWH = 52

Can you help me with the math to help explain the difference in charge kWH of the two trips versus EPA ratings? I understand the difference in Wh/rm explains a lot of this to me but not all.

TIA

 

[AlanSubie4Life]

Elevation change: +800 feet
-Odometer miles = 222
-Range miles = 274 (306@99% - 32@10%)
-Trip Wh/rm = 272
-Trip kWH = 60
-SC kWH = 64

Battery:
~220Wh(trip)/rmi*274rmi = ~60.3kWh
Trip:
272Wh(trip)/mi*222mi = 60.4kWh

I don’t know anything about Supercharger behavior but the excess probably is just heat loss and accessories. Note the efficiency is pretty high since conversion losses don’t really exist (not charged for directly I guess).

Weather: Sunny and 68->72
-Elevation change = -800 feet
-Odometer miles = 255
-Range miles = 253 (303@98% - 50@16%)
-Trip Wh/rm = 224
-Trip kWH = 57
-Home Charger kWH = 52

220Wh/rmi*253rmi = 55.7kWh

224Wh/mi*255mi = 57.2kWh (trip)

A bit of error here. Was your battery chilly to start with? A little battery warming can add a few miles (even with no snowflake), and that would explain the discrepancy.

For the home charge to explain that I would have to know what rated miles you finished at.

 

[jdcollins5]

Battery:
~220Wh(trip)/rmi*274rmi = ~60.3kWh
Trip:
272Wh(trip)/mi*222mi = 60.4kWh

I don’t know anything about Supercharger behavior but the excess probably is just heat loss and accessories. Note the efficiency is pretty high since conversion losses don’t really exist (not charged for directly I guess).

Is the 220wh/m constant from the 219 Trip Constant in your spreadsheet?


220Wh/rmi*253rmi = 55.7kWh

224Wh/mi*255mi = 57.2kWh (trip)

A bit of error here. Was your battery chilly to start with? A little battery warming can add a few miles (even with no snowflake), and that would explain the discrepancy.

For the home charge to explain that I would have to know what rated miles you finished at.

Is the 220 Wh/m from the 219 Trip Constant in your spreadsheet?

I finished at 50 miles. It is in the Range miles in my post in parenthesis.

What would my kWH be at 100% for each of the two trips versus rated?

Thanks

 

[AlanSubie4Life]

Is the 220 Wh/m from the 219 Trip Constant in your spreadsheet?

Yeah. That is an approximate number. It was from memory...guess I should have used 219Wh/rmi. But there is some variation around that. And at this time of year when the battery changes from cool to hot it tends to end up being high. Because of that rated mile growth with temperature issue I mentioned.

finished at 50 miles. It is in the Range miles in my post in parenthesis.

I meant what did you finish the charge at home at?

 

[jdcollins5]

Yeah. That is an approximate number. It was from memory...guess I should have used 219Wh/rmi. But there is some variation around that. And at this time of year when the battery changes from cool to hot it tends to end up being high. Because of that rated mile growth with temperature issue I mentioned.



I meant what did you finish the charge at home at?

OK, finished charge at home at 89%.

 

[AlanSubie4Life]

OK, finished charge at home at 89%.

I am going to assume that what you quoted (52kWh) was what was on the charge screen?

Because 275-50 = 225rmi

225rmi*234Wh/rmi = 52.7kWh. Which is pretty close.

Note that this is DC kWh and does not represent the wall kWh. For you, the wall kWh was probably about:

225rmi*223Wh/rmi/0.885 = 56.7kWh

 

[jdcollins5]

I am going to assume that what you quoted (52kWh) was what was on the charge screen?

Because 275-50 = 225rmi

225rmi*234Wh/rmi = 52.7kWh. Which is pretty close.

Note that this is DC kWh and does not represent the wall kWh. For you, the wall kWh was probably about:

225rmi*223Wh/rmi/0.885 = 56.7kWh

Sorry. I should have specified that I have a kWH meter on my charge circuit. So the 52 kWH is from the AC side.

 

[AlanSubie4Life]

Sorry. I should have specified that I have a kWH meter on my charge circuit. So the 52 kWH is from the AC side.

Well, I really cannot make sense of that number, then! It seems really considerably lower than I would expect for a charge from 50rmi to 275rmi.

 

[jdcollins5]

Well, I really cannot make sense of that number, then! It seems really considerably lower than I would expect for a charge from 50rmi to 275rmi.

That is where I am having a problem too!

The first, cold trip took 64 kWH DC to charge from 32rmi to 307rmi = 275rmi.

The second, warm trip took 52 kWH AC to charge from 50rmi to 275rmi = 225rmi.

Well when I look at it this way, 275/225 = 1.22. 1.22 X 52 = 63.55 kWH. Close enough except one is on the AC side and the other is on the DC side.?

If I look at battery kWH at 100%:

First trip: 275rmi/310rmi = 0.89, 64kWH/0.89 = 71.9kWH

Second trip: 225rmi/310rmi = 0.73, 52kWH/0.73 = 72.6kWH.

I guess my question now is the SC reported kWH from the car BMS or from the SC? Is it the AC side or DC? It would make sense from a billing standpoint to be from AC side. Thoughts? I was not charged for SC so I do not have a receipt to review. Only what was reported as added on the car charge screen.

 

[AlanSubie4Life]

The second, warm trip took 52 kWH AC to charge from 50rmi to 275rmi = 225rmi.

There has to be something wrong with this datapoint.

The amount of energy added to the battery should have been: 223Wh/rmi*225rmi = 50.2kWh

But there are conversion losses. I would expect about 90% efficiency (what sort of charge rate do you use?) based on data from Tesla. So that would be 55.7kWh.

(If no issue with data, next time measure voltage, current, and time, just to check the meter accuracy...)

I’ve checked this a fair amount myself so I am fairly sure of the numbers but who knows...

Only what was reported as added on the car charge screen.

What is on the charge screen (in my experience) was just the number of miles added * charging constant for your vehicle. Also does not quite align. They may have changed this recently though, because of their change in how they bill. Have not Supercharged since that change. So they may display total power use including accessories during a Supercharging event now.

I also have never Supercharged with significant accessory use and paid attention to the metering at the same time. Only time I paid attention was with minimal accessories in use.

 

[jdcollins5]

There has to be something wrong with this datapoint.

The amount of energy added to the battery should have been: 223Wh/rmi*225rmi = 50.2kWh

But there are conversion losses. I would expect about 90% efficiency (what sort of charge rate do you use?) based on data from Tesla. So that would be 55.7kWh.

(If no issue with data, next time measure voltage, current, and time, just to check the meter accuracy...)

I charge with a 14-50 at 240V, 32A and 30 mph. The voltage at charge is about 236V. I can take the range miles to be added and divide by 4.2 mi/kWH (~238wh/mi) and come very close to the AC kWH to be added every time.

What is on the charge screen (in my experience) was just the number of miles added * charging constant for your vehicle. Also does not quite align. They may have changed this recently though, because of their change in how they bill. Have not Supercharged since that change. So they may display total power use including accessories during a Supercharging event now.

I saw that change in Tesla’s billing and this is my first time at SC since the change..