Wire type

[rjpjnk]

Consider that if this is a new 50A circuit then per the 2017 revision of the NEC the circuit breaker needs to be a 50A GFCI breaker (~$100)

For less than what the JuiceBox 40A EVSE will cost you could purchase the Tesla Wall Connector ($500). When you hard wire you don't need to use a GFCI circuit breaker (saves you $100.) The Wall Connector can be used on any of 15/20/30/40/50/60 amp circuits. If you perform a load calculation you may be able to install a 60A breaker, then the Wall Connector can enable charging at up to 48A. When used with a 50A circuit the Wall Connector enables charging at up to 40A (same as the JuiceBox 40.)

This is what I would do as well.

 

[rjpjnk]

At Level 2 (240V) and up to 48A it hardly matters as you are charging at well below 1C, closer to .1C.

What is C?

 

[Sophias_dad]

What is C?

What Is A Battery C Rating & How Do I Calculate C Rate - Power Sonic

Power Sonic look at what a battery C Rating is and how that C Rate is calculated. Includes battery C Rate charts, formulas and examples.

www.power-sonic.com

 

[jcanoe]

What is C?

C is the abbreviation for the total capacity of the battery. I.e. The 2021 Tesla Performance Model Y is known to have a battery pack with a total capacity of 82kWh. 1C would be a charging rate (or discharging rate) of 82kW. Keeping to under 1C is better for the life and health of the lithium battery or battery pack. In this case 2C would be a ~160kW charging rate.

Tesla understands how to maximize the charging rate, exceed 2C for part of the charging cycle without damaging the Tesla vehicle's battery. Tesla does this by ramping up the charging amperage and voltage, sustaining peak charging for a limited amount of time before tapering off the charging rate. Active temperature management of the battery pack while Supercharging ensures that the battery temperature it tightly regulated throughout the charging cycle.

Tesla tracks the Supercharger usage of every Tesla vehicle and battery pack. If a Tesla vehicle is frequently charged using a Supercharger Tesla may, at some point, limit the maximum Supercharging rate to ensure that the battery pack continues to provide acceptable performance and range.

 

[rjpjnk]

Thanks for the explanation. Just a little unclear if C is capacity or “capacities per hour”.

Is C the total capacity (energy) of a given battery in kWh, then the safe charge rate (power) to stay below would be 1C/hour, which has units of kW, correct?

 

[jcanoe]

Thanks for the explanation.
So C is the total capacity (energy) of a given battery in kWh, and the safe charge rate (power) to stay below would be 1C/hour, which has units of kW. Correct?

Correct. If the battery was smaller, i.e. for an RC racer then the capacity of the battery would be stated in watt hours (Wh) instead of kWh, the charging rate would be expressed in watts.

 

[rjpjnk]

Sophias_dad set me straight above, thanks for the link!

So it appears C is not capacity, It is rate in capacities per hour. That clears it up.

 

[jcanoe]

Sorry, I was editing while you were answering.

Please read my edited version. 1C = capacity of 1 battery, and 1C/hour is the charge rate, correct?

I ask this because I read the phrase “charging at 1C” and wondered if you meant 1C/hour.

C is the total energy capacity of the battery in kilowatt hours (kWh). For an 82kWh battery if you charge at 1C you would be charging at 82kW. The hours drop off leaving just the kW (power level in kilowatts)

 

[Cobe]

I have a quick question if you have a few minutes (and I have limited electrical knowledge).

Electrician just installed wall charger on 60A circuit last week. I noticed MY is charging at 48 amps. Is that normal, or should/could it charge at 60 amps? Thanks so much!

 

[jcanoe]

I have a quick question if you have a few minutes (and I have limited electrical knowledge).

Electrician just installed wall charger on 60A circuit last week. I noticed MY is charging at 48 amps. Is that normal, or should/could it charge at 60 amps? Thanks so much!

Your Tesla Wall Connector is configured correctly, working as designed. When charging any EV the maximum amperage allowed by the electrical code (NEC) is limited to 80% of the circuit rating. 80% of 60A is 48A. 48A also happens to be the maximum charging amperage for the Gen3 Wall Connector.

 

[Cobe]

Your Tesla Wall Connector is configured correctly, working as designed. When charging any EV the maximum amperage allowed by the electrical code (NEC) is limited to 80% of the circuit rating. 80% of 60A is 48A. 48A also happens to be the maximum charging amperage for the Gen3 Wall Connector.

Thanks jcanoe, appreciate the information and confirmation that all is well! Having our first Tesla is a "discovery" process and I am enjoying all the embedded tech in the vehicle. Hope your experiences are always enjoyable!

 

[roblab]

that is the interesting thought too.... miles per day will be less than 15 once we go back to work (working from home right now).

Is it better to charge slow and steady than rapid and quick?

I could just keep everything as is.... 40 amp with 240 and 14-50 receptacle.

Slow and steady is better for the battery. My car charges at night, so I never know just how long it takes, and unless you're up driving, you could take literally hours to charge. No need to quick charge.