EV Charging
Some Notes on EV charging, chargers and other miscellany
Sizing table for a home EV charger
So the average longer range EV's these days have battery packs that are generally between 50 and 100 KWH. That being said, if you are at home it is highly unlikely you will ever put more than 50KWH into your car in a single charging session. At 3.5 miles / KWH that's around 175 miles (in a day).
| Wire | Rated Amps | Charging Amps | Watts @ 120V | Time (Hours) for a 50KWH Charge | Watts @ 240V | Time (Hours) for a 50KWH Charge |
|---|---|---|---|---|---|---|
| 14 | 15 | 12 | 1400 | 35 | 2800 | 18 |
| 12 | 20 | 16 | 1900 | 27 | 3800 | 14 |
| 10 | 30 | 24 | 2800 | 18 | 5700 | 9 |
| 8 | 40 | 32 | – | – | 7600 | 7 |
| 6 | 50 | 40 | – | – | 9500 | 6 |
| 4 | 60 | 48 | – | – | 11000 | 5 |
Generally the highest amperage 110/120v plug is 30A, this chart reflects that. Note that you should not sustain a rated breaker at more than 80% of it maximum rating for any significant period of time. If you do, it will heat up and trip, and you will likely damage it over time. Further your home “charger” is not a charger at all. It's a control box that informs the actual charger built into the car about how much electricity it is allowed to use. This means that your charging limit is based on the charging unit in the car, most of which run about 7.5KW, with newer models creeping into the 9KW range. I believe Tesla's may actually have an 11KW unit, I haven't looked.
As you can see, the overall time does not drop significantly on each step once you get past 30A. The biggest leap is when you go to “Level 2” charging, where you run a 220/240V outlet instead of 110/120V. Depending on labor costs, and what you have in your panel, from an expense and simplicity standpoint the sweet spot is usually around a 240/30 circuit, as most folks are generally at home for 9 hours in the evening. Also note that as your charge get's closer to 100% your charging rate will slow down. In other words your last 10% or so of charge will take significantly longer, as your charging rates go lower.
