Can someone help me understand how my battery is possibly 75 kWh?

[AlanSubie4Life]

The usable energy in the Model 3 LR is more like 72.5kwh. So lets say 72kwh

That is not correct, when new. 72kWh usable *not including buffer* is quite common for a vehicle a few months old. That corresponds to an AWD 2018/2019 showing 310 rated miles at a full charge (again, not including buffer - if you include buffer that vehicle would have 75.3kWh available *as measured by the trip meter* -76kWh*0.99). 310rmi*245Wh/rmi*0.955*0.99 = 71.8kWh is what you would see on the trip meter for a 310rmi to 0 rmi discharge. As shown, you could extract about 75kWh on the trip meter if you went deep into the buffer.

And remember when the car is new, it effectively has even more energy than that, even though it shows 310 rated miles, because the energy per rated mile is slightly inflated when new (so you have to use a higher constant than 245Wh/rmi above). That is why 2018/2019 vehicles generally did not show range loss for the first few months.

72.5 usable energy in battery is from Teslabjorn, who has tested Teslas for years and years. He has done a usable battery test on the Model 3.

I’m sure he did a good test, but you need to link to the video. This is not correct for a NEW vehicle. It is perfectly normal for a typical vehicle 6-12 months old. You can DEFINITELY get more than 72.5 kWh out of a new vehicle (as displayed on the trip meter). The max you will see on the trip meter, assuming driving deep into the buffer (below 0!) is about 75kWh for a new vehicle (see above). If it is brand new you *might* see 76kWh *if you nearly fully use the buffer* (not recommended!). (78kWh*0.99 = 77.2kWh is theoretical maximum using the full buffer.) Driving to 0rmi on a new vehicle you will see a minimum of about 72.8kWh, not including the buffer (77kWh*0.955*0.99). The minimum you will see if your vehicle displays 309/310 rated miles but is *NOT* new (meaning it has lost 2% capacity but still shows about 310 rated miles) is about 71.7kWh (not including use of the buffer) (75.8kWh*0.955*0.99). Again, these “minimums“ assume no energy lost in park! Continuous discharges from max to min only, with no stopping (if you stop you have to remove any miles used when in park from the calculation and extrapolate to what you would have seen).

I never did this on my vehicle (100% to 0%) but when it was a couple months old I did a 93% to 11% discharge and it was on target for about 73kWh, not including the buffer. (Obviously this is imprecise, but clearly demonstrates that for a new vehicle you can get more than 72.5kWh including the buffer.)


Again, with all of above, note that the trip meter “loses” about 1% of the energy, as compared to what the CAN bus says is available (deltas in CAN bus energy will be higher than trip meter by about 1% - even if no energy is lost while in park).

So a trip meter reading of 72kWh corresponds to closer to 72.7kWh of actual CAN bus energy content used.

 

[Gasaraki]

That is not correct, when new. 72kWh usable *not including buffer* is quite common for a vehicle a few months old. That corresponds to an AWD 2018/2019 showing 310 rated miles at a full charge (again, not including buffer - if you include buffer that vehicle would have 75.3kWh available *as measured by the trip meter* -76kWh*0.99). 310rmi*245Wh/rmi*0.955*0.99 = 71.8kWh is what you would see on the trip meter for a 310rmi to 0 rmi discharge. As shown, you could extract about 75kWh on the trip meter if you went deep into the buffer.

And remember when the car is new, it effectively has even more energy than that, even though it shows 310 rated miles, because the energy per rated mile is slightly inflated when new (so you have to use a higher constant than 245Wh/rmi above). That is why 2018/2019 vehicles generally did not show range loss for the first few months.



I’m sure he did a good test, but you need to link to the video. This is not correct for a NEW vehicle. It is perfectly normal for a typical vehicle 6-12 months old. You can DEFINITELY get more than 72.5 kWh out of a new vehicle (as displayed on the trip meter). The max you will see on the trip meter, assuming driving deep into the buffer (below 0!) is about 75kWh for a new vehicle (see above). If it is brand new you *might* see 76kWh *if you nearly fully use the buffer* (not recommended!). (78kWh*0.99 = 77.2kWh is theoretical maximum using the full buffer.) Driving to 0rmi on a new vehicle you will see a minimum of about 72.8kWh, not including the buffer (77kWh*0.955*0.99). The minimum you will see if your vehicle displays 309/310 rated miles but is *NOT* new (meaning it has lost 2% capacity but still shows about 310 rated miles) is about 71.7kWh (not including use of the buffer) (75.8kWh*0.955*0.99). Again, these “minimums“ assume no energy lost in park! Continuous discharges from max to min only, with no stopping (if you stop you have to remove any miles used when in park from the calculation and extrapolate to what you would have seen).

I never did this on my vehicle (100% to 0%) but when it was a couple months old I did a 93% to 11% discharge and it was on target for about 73kWh, not including the buffer. (Obviously this is imprecise, but clearly demonstrates that for a new vehicle you can get more than 72.5kWh including the buffer.)


Again, with all of above, note that the trip meter “loses” about 1% of the energy, as compared to what the CAN bus says is available (deltas in CAN bus energy will be higher than trip meter by about 1% - even if no energy is lost while in park).

So a trip meter reading of 72kWh corresponds to closer to 72.7kWh of actual CAN bus energy content used.

Yes, usable means doesn't include buffer, cause you can't use the buffer.

That is the "too long, didn't watch" link. He says he expect 73kwh from an new Model 3 from all his other testing.

 

[gaswalla]

folks that want this data need to hook up the cables behind the drivers seat, use TMSpy or ScanMyTesla and then get legit numbers that are not extrapolated from 4 other extrapolated set of numbers

 

[AlanSubie4Life]

cause you can't use the buffer.

You can use the buffer (but it is certainly not recommended unless you are slowly circling a parking lot with a charger within reach of the vehicle at all times). Bjørn demonstrates this in some of his videos I think (and there are numerous other ones on YouTube).

Here is one, starting at about 24 minutes, ending somewhere 20+ minutes later. You can see he resets the trip meter upon hitting 0km, then drives 20km at 136Wh/km.

As I said, strongly, strongly, not recommended - the car can shut down unexpectedly at any time - the higher the speed the more likely it is. But it is not impossible. And indeed, this is what Tesla does when they range test the car for the EPA! They drive until the vehicle stops moving - they certainly don't stop at 0km! Gotta use up that energy! That is how they consistently extract 79kWh from a vehicle with 4000 miles on it.

 

[AlanSubie4Life]

folks that want this data need to hook up the cables behind the drivers seat, use TMSpy or ScanMyTesla and then get legit numbers that are not extrapolated from 4 other extrapolated set of numbers

Yep. Fortunately a lot of other people have done this and the numbers are now well understood. The confusion arises primarily around 1) the buffer (which can be used, possibly, but should never be), and 2) the slight undercounting by the trip meter, and 3) the use of energy while the car is in park. Those are the places where people lose the thread.

Tesla's method of displaying rated range is great - because assuming your BMS & battery isn't completely failing, you always know exactly how far you can go at a given consumption level, once you know how it works (which is actually really simple). They always tell you exactly how much energy you have left, even without any fancy tools! Just find your constant for your vehicle (located at TMC - easy to look up - or just measure it yourself with a calibrated long trip), then do the math. Super simple. It's just a simple multiplication of rated range remaining by the ratio of the constant and your average consumption to give you your potential range.

Range to 0 rated miles = Rated range remaining * (vehicle constant / target average consumption)

Obviously you can flip this around to tell you your target for average consumption needed to make a destination (useful at Superchargers if you know how you've been doing and what sort of consumption to expect on the next leg):

Target consumption = Rated range at end of Supercharging event * (vehicle constant / Distance to next charger)

You must do better than the target consumption to arrive at your destination with greater than 0 rated miles (so add some margin!).

 

[hari-bhari]

Thanks so much for the help!

 

[Candleflame]

oh god here we go again. A lot of the posts are just plain wrong.

View attachment 587618 I have a LR RWD and stated mileage capacity of 312 miles on a full charge. I keep the battery indicator on percentage mode normally.

BUT, no matter how many times I divide my kWh used by battery percentage used, I get somewhere between 63-68 kWh. I have even charged to 90% and discharged to 10% to allow it to calibrate. I thought maybe phantom drain even though I switched off sentry and summon.

Today I drove 146 miles and used 66% of my battery (from 95% to 29% after a 100% overnight charge) and 45.14 kWh which comes to 68.4 kWh capacity. Efficiency was 315 wh/mi (I had a full car going 85 mph), so 146-66% = 221 miles per full charge. This is also lower than I would expect (240wh/310 miles x 315wh = 243 miles)

What gives?? If my battery capacity was degraded the full meter wouldn’t show 312 miles. I don’t understand what’s going on.

Driving isn't a particularly accurate way to measure battery degradation, the best way is to discharge it and charge it back up to 100% to see how much it holds.

A full battery holds 75 kwh + 4.5% of that as a buffer on the bottom (sub 0%) + brick protection which noone has access to.

Your BMS currently calculates that you have 312 /322 = around 3.1% degradation. That is a fantastic number for a 3 year old Model 3. The closer your battery gets to 0% the more the car will behave as if it has 322 miles available.
So you have around 72.7kwh available which sounds about right for a RWD that old.
Getting around 69kwh without doing a deep discharge doesnt sound too far off. The car always seems to be off a little bit with discharge kwh due to varying factors i.e. heat losses and idle losses.

This is a good example of charging a reasonably new Model 3 at 4985km.

you can see a quick charge up to 4% to avoid rounding error when starting to charge. Following by a charge from 4 - 91% dumping 66.75kwh into the battery for an extrapolated capacity at 0 - 100% of 76.72kwh, could probably knock a kwh off re rounding errors as I was charging a hot pack for a total capacity of 76kwh which is about right - I had a better than average pack when the car was delivered and Most cars come with 76kwh usable capacity which quickly degenerates to 75kwh within 2-3 months of ownership.

EDIT: I have attached you the drive just before this DC charging session:

you can see I was starting at 78% driving down to 3% and the car estimated that I used 15.7+35.3 (51kwh) so that is 51 / 0.75 = 68kwh which is actually similar to your number. I guess if you drive it from 100% to 0% it becomes a bit more accurate but it is just to show that the BMS doesnt always exactly know how many electrons you can get out of the battery and there are losses the BMS cannot account for. The only thing which matters is how many kwh you can put back into the battery at the end of your journey.

Also interesting that during the AC charge beforehand if you extrapolate the charge the capacity is 75.1kwh which again fits with the true amount the pack holds (33% recharge depth is of course not very accurate)

 

[AlanSubie4Life]

you can see a quick charge up to 4% to avoid rounding error when starting to charge. Following by a charge from 4 - 91% dumping 66.75kwh into the battery for an extrapolated capacity at 0 - 100% of 76.72kwh,

You realize that TeslaFi simply multiplies the API km added by 153Wh/rkm to give you the energy added, right? (You have an AWD I guess.)

TeslaFi does not have access to the CAN and has no idea how many kWh were added. It just uses the (incorrect) constant, just like the car does.

If you had SMT for this charge, it would have likely indicated that 145.4Wh/km*436.45
rkm = 63.5kWh were added. That is the BMS constant per rated km we have seen.

If you have it, you should cross check!

This is entirely consistent: you added 87% and added 63.5kWh. This means your 0-100% was about 72.9kWh (63.5kWh/0.87), some rounding error.

This means your total battery capacity was 72.9kWh/0.955 = 76.3kWh including the buffer.

This is entirely consistent with a vehicle that is quite new (it would have shown no rated km degradation at the time of this charge).

Everything checks out.

and the car estimated that I used 15.7+35.3 (51kwh) so that is 51 / 0.75 = 68kwh

Remember that the used kWh in TeslaFi is user-scalable (you can configure it to tell you whatever you want, apparently!) and notoriously inaccurate compared to the trip meter.

Log numbers from the trip meter to ensure they exactly align. Check it if you don’t believe me, of course; I am just a guy on the Internet.

Your BMS currently calculates that you have 312 /322 = around 3.1% degradation.

He started at 325 rated miles with ~78kWh (not 76kWh when brand new!). (Actually with a RWD before range update he had more like 310rmi/74kWh or so available but that is kind of artificial to use that as the start point, as they seem to have just unlocked capacity later - special case - have to look at *actual* capacity loss).

So if it was 312rmi for 100% it is 234Wh/rmi*312rmi = 73kWh.

So 6% loss. Totally normal for a car this age. Quite good.

And virtually no change in user-available energy vs. when the car was new (due to the range update). But again, that is the wrong way to look at degradation when comparing across vehicles.

 

[Dogtone]

The sticker from my 2019 AWD says 74 kWh

 

[Candleflame]

You realize that TeslaFi simply multiplies the API km added by 153Wh/rkm to give you the energy added, right? (You have an AWD I guess.)

TeslaFi does not have access to the CAN and has no idea how many kWh were added. It just uses the (incorrect) constant, just like the car does.

If you had SMT for this charge, it would have likely indicated that 145.4Wh/km*436.45
rkm = 63.5kWh were added. That is the BMS constant per rated km we have seen.

If you have it, you should cross check!

This is entirely consistent: you added 87% and added 63.5kWh. This means your 0-100% was about 72.9kWh (63.5kWh/0.87), some rounding error.

This means your total battery capacity was 72.9kWh/0.955 = 76.3kWh including the buffer.

This is entirely consistent with a vehicle that is quite new (it would have shown no rated km degradation at the time of this charge).

Everything checks out.



Remember that the used kWh in TeslaFi is user-scalable (you can configure it to tell you whatever you want, apparently!) and notoriously inaccurate compared to the trip meter.

Log numbers from the trip meter to ensure they exactly align. Check it if you don’t believe me, of course; I am just a guy on the Internet.



He started at 325 rated miles with ~78kWh (not 76kWh when brand new!). (Actually with a RWD before range update he had more like 310rmi/74kWh or so available but that is kind of artificial to use that as the start point, as they seem to have just unlocked capacity later - special case - have to look at *actual* capacity loss).

So if it was 312rmi for 100% it is 234Wh/rmi*312rmi = 73kWh.

So 6% loss. Totally normal for a car this age. Quite good.

And virtually no change in user-available energy vs. when the car was new (due to the range update). But again, that is the wrong way to look at degradation when comparing across vehicles.

Teslafi assumes 143w/km per rated mile which I changed to 150w/km but I think back then I just got it new so it uses 143 still now that i think of it.