MASTER THREAD: 2021 Model 3 - Charge data, battery discussion etc

[Jejunjm]

I have to admit I don't know what internal resistance means. My misspent undergraduate degree brain only remember that as you approach absolute 0 materials become more conductive (ie search for a room temperature superconductor)

 

[AAKEE]

I have to admit I don't know what internal resistance means. My misspent undergraduate degree brain only remember that as you approach absolute 0 materials become more conductive (ie search for a room temperature superconductor)

If you think like this:

A battery which you measure the voltage when it is in rest will show the dormant( right expression?) voltage, voltage without any load. For example a fully charged li ion NCA like Teslas Panasonic cells will read 4.20V. Thats the definition of 100% SOC.

If you take a 100% cell and connect it to a 5 Watt lamp, the voltage vill drop a little. If you connexct a 10W lamp to the battery instead, the voltage will drop furter. The reason for the drop is the internal resistance. The higher the internal resistance, the higher the voltage drop.

Internal resistance increases at low temps and reduces at higher temps.
If you put a AA/AAA or LR6 (etc) in the fridge for a couple of hours and then take it out and try to use it in a electric toy etc, it will perform bad until the temperature comes up in the cell.

If you try to charge a battery you need to increase the voltage supplied above the cells voltage reading to get a flow of energy to the battery.
The higher the voltage, the higher the current. But the internal resistance works like a ”brake” and hinders the current.
The higher the internal resistance, the lower the current= slower charge.
As there is a maximum voltage limit for each cell supply voltage, it is the internal resistance that limits the charging power as soon as this voltage limit is reached. 4.2V/cell times 96 in series = 403V.
When 403V is reached in a SuC supply, the internal resistance set the charging speed.
(Below the 403V, its Tesla that limits the current to safe levels for the battery.)

Preheating the battery reduce the internal resistance and alloww higher current. Also, a 40C ( and plus) battery will get less wear from fast charging.

 

[OlaM]

About charging in the cold, why is it that the battery can take very low charging speed when cold but you can still drive and have a higher kW output? Is discharging easier on the chemistry?

 

[AlanSubie4Life]

About charging in the cold, why is it that the battery can take very low charging speed when cold but you can still drive and have a higher kW output? Is discharging easier on the chemistry?

Yes

(Elaborating, lithium plating is an issue when charging as I understand it (due to excessive concentration of lithium ions around the anode without proper intercalating?) but not an issue on discharge for the reverse process.)

 

[AAKEE]

About charging in the cold, why is it that the battery can take very low charging speed when cold but you can still drive and have a higher kW output? Is discharging easier on the chemistry?

As @Alansubie says, the battery probably can physically receive quite high current/power when charging in the bottom of the SOC, and Tesla probably limits the power to *not get* too much lithium plating.

At higher SOC levels, the internal resistance limits the charging current/power.

To deliver power, the battery has full voltage to “overcome” the internal resistance. For example 400V divided by I ternal resistance = the resulting current.

When charging, it’s the difference between supplied voltage and the battery voltage that gives the resulting current/power.
If the battery has low SOC, the difference can be 100V giving high currents.
As the SOC raises, the battery voltage also does but the charging voltage can not be higher than 4.20V/cell(= 403V with Panaonic cells).
At 50% SOC we are at 363V or so, and the “charging force” is only about 40V so the amps/charge power goes down.

 

[snowthewitch]

Can you start your tesla while it's charging? I assume you can.

Say I leave it plugged in each night, but wake up in the morning to heat up the car. Any issues?

 

[Bouba]

Can you start your tesla while it's charging? I assume you can.

Say I leave it plugged in each night, but wake up in the morning to heat up the car. Any issues?

You can heat the interior, including seats and steering wheel, while still plugging in. I don’t think you can drive it while plugged in but the computer, aircon etc can be used

 

[OlaM]

Thanks for the cold charging replies.

Picked up my Model 3 today. Haven't looked for the sticker, but the code that showed up in the registration docs was E5LD, so it's a nice new LG 82 for me! Very happy about that and happy with the whole car.

Ordered Oct 8 by the way, shipped from China Oct 21.

 

[Matt3M3]

Thanks for the cold charging replies.

Picked up my Model 3 today. Haven't looked for the sticker, but the code that showed up in the registration docs was E5LD, so it's a nice new LG 82 for me! Very happy about that and happy with the whole car.

Ordered Oct 8 by the way, shipped from China Oct 21.

Do you have a way to see the nominal full pack ? I could have the 82 kWh but in total (I think usable) I have 78.7… actual now the app show me 78.5 kWh

 

[OlaM]

Do you have a way to see the nominal full pack ? I could have the 82 kWh but in total (I think usable) I have 78.7… actual now the app show me 78.5 kWh

Soon, I have an OBD2 reader coming in the mail. 82 is never net 82 usable is it? High 70s is good for the "82" as far as I understand it.

 

[opasenBG]

Hi all,

Not sure if this is the right place to ask this question but I looked around and could not find a better one.

We have a L15-30 250V 30A 3phase outlet available at work and was wondering if I can charge off of it. The photos show the available plug and receptacle used at work.

I've found this adapter plug(see link below) which suggests I can but wanted to check if anyone out there is using such setup.
L15-30 to 14-50 Adapter plug

Your help would be greatly appreciated.

 

[theothertom]

Say I leave it plugged in each night, but wake up in the morning to heat up the car. Any issues?

I do that every morning using the Tesla app on my phone. Doesn't matter if the car is plugged in or not.

 

[theothertom]

We have a L15-30 250V 30A 3phase outlet available at work

I don't think EVSEs (aka chargers) in the US are set up for 3 phase. I think they use 3 phase chargers in Europe, though. Maybe someone else knows better than me.

 

[Dave EV]

I don't think EVSEs (aka chargers) in the US are set up for 3 phase. I think they use 3 phase chargers in Europe, though. Maybe someone else knows better than me.

That is true - can't charge off all 3-phases in the USA because the USA plug only has 2 poles.

But, if you have charged on a L2 charger that reads ~208V, you have charged on 2 of 3 phases of a 3 phase power supply. Most USA commercial buildings are powered with 3 phase 208V power where there is 120V between each hot wire and neutral, and 208V between each hot wire.

So if you have a 4-plug 3-phase 208V plug, you just need an adapter that taps two of the hot wires and you can just ignore the 3rd hot wire.

In the pics above, I'm a bit concerned that I see a white wire on a L15-30 receptacle. White should only be used for neutral lines unless otherwise marked. Typically a 3-phase wire would use black, red and blue for the hot wires. If it is indeed a hot wire, it should be marked with electrical tape, usually black or red.

 

[Paige111]

How do you get your CoC? Can I request it before paying?

They should be required to give the customer CoC in USA, its ridiculous how they can get away w/putting any size battery in the 3 & not tell the customer, they say it’s proprietary info, they cant tell the customer. My only request was for the 82KWH battery, per my VIN decoding Im suppose to have the BT42 (82KWH). Im sure Tesla would tell me my battery size if it was 82KWH, but they always just give me inconsistent, inaccurate responses ( one T support said it was a 65kwh CATL) If I had known it wasnt a 82KWH battery, I wouldnt of bought the car.

It will be interesting to see what your rated range displays once you collect the car. I received mine (UK) on the 11th December and it has never displayed the rated range. I think the most it ever did was 340 miles.

How do you get your CoC? Can I request it before paying?

 

[opasenBG]

That is true - can't charge off all 3-phases in the USA because the USA plug only has 2 poles.

But, if you have charged on a L2 charger that reads ~208V, you have charged on 2 of 3 phases of a 3 phase power supply. Most USA commercial buildings are powered with 3 phase 208V power where there is 120V between each hot wire and neutral, and 208V between each hot wire.

So if you have a 4-plug 3-phase 208V plug, you just need an adapter that taps two of the hot wires and you can just ignore the 3rd hot wire.

In the pics above, I'm a bit concerned that I see a white wire on a L15-30 receptacle. White should only be used for neutral lines unless otherwise marked. Typically a 3-phase wire would use black, red and blue for the hot wires. If it is indeed a hot wire, it should be marked with electrical tape, usually black or red.

Thanks for the detailed info!
I measured the outlet some time ago and if I remember correctly it showed 120V. Now I wonder if this perticular one is 14-30.
I'll check again on Monday and report back.

 

[Bouba]

They should be required to give the customer CoC in USA, its ridiculous how they can get away w/putting any size battery in the 3 & not tell the customer, they say it’s proprietary info, they cant tell the customer. My only request was for the 82KWH battery, per my VIN decoding Im suppose to have the BT42 (82KWH). Im sure Tesla would tell me my battery size if it was 82KWH, but they always just give me inconsistent, inaccurate responses ( one T support said it was a 65kwh CATL) If I had known it wasnt a 82KWH battery, I wouldnt of bought the car.

That is exactly what happened to me. I considered canceling as a silent protest against the system but what’s the point ? So, either get the car I didn’t want (75 kWh) or keep driving the Volvo. I bought the Tesla

 

[AAKEE]

I see that my teslafi range( in the battery degradation report) varies quite much despite that the Nominal Full Pack is steady at the same level. Do we know why the teslafi range varies like this?

Also, at a quite long time during the autumn I had a NFP of 80.3-80.4 kWh and the max range in Scan My Tesla was mostly about 503-504km. The teslafi range was about the same. Now the NFP is above 81kWh, the SMT max range is 507-509km but the teslafi shows a lower range(about 500-502km). I have tried to find the reson for the lower range, it doesnt seem to be the temperature as I can have days with the same NFP but the temperature and the range doesnt show any consistence in the changes.

 

[ran349]

I see that my teslafi range( in the battery degradation report) varies quite much despite that the Nominal Full Pack is steady at the same level. Do we know why the teslafi range varies like this?

Also, at a quite long time during the autumn I had a NFP of 80.3-80.4 kWh and the max range in Scan My Tesla was mostly about 503-504km. The teslafi range was about the same. Now the NFP is above 81kWh, the SMT max range is 507-509km but the teslafi shows a lower range(about 500-502km). I have tried to find the reson for the lower range, it doesnt seem to be the temperature as I can have days with the same NFP but the temperature and the range doesnt show any consistence in the changes.

SMT reads the NFP directly, while Teslafi has to calculate the battery capacity from the rated miles reading and percent SOC that it gets from the API. The percent SOC from the API is only given as a whole number, so there will be more variation in the Teslafi value due to the rounding error.
The max range in SMT is also an estimate, because the SMT rated miles is only read as a whole number.

 

[AAKEE]

SMT reads the NFP directly, while Teslafi has to calculate the battery capacity from the rated miles reading and percent SOC that it gets from the API. The percent SOC from the API is only given as a whole number, so there will be more variation in the Teslafi value due to the rounding error.
The max range in SMT is also an estimate, because the SMT rated miles is only read as a whole number.

Thank you, very good info!