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Electric Vehicle Supply Equipment
(EVSE)
Equipment that supplies electricity to an EV
There are three types of EVSE, distinguished by supply power voltage.
Supply power (kW) is the product of voltage (V) and current in amperes (A).
For a given EVSE voltage, amperage determines the charging supply power.
AC Level 1
Alternating current (AC) electricity supplies power at 120 volts to the EV.
The EV battery is actually charged by direct current (DC) electricity from an onboard inverter that coverts AC input into DC input for the battery.
Level 1 charging at 20 amps supplies 2.4 kW, well below the onboard inverter capacity.
The range restored depends on the EV fuel economy:
A 0.29 kWh/mile EV needs 11.6 kWh to restore 40 miles. At 2.4 kW, this takes ~5 hours.
AC Level 1 EVSE is generally not used for public charging, but allows EV drivers to charge at home without upgrades.
AC Level 2
AC electricity is supplied at 240 volts from a dispenser (pedestal or wall-mounted).
Here, the onboard inverter controls the rate at which an EV accepts power (20-100 A).
A 0.29 kWh/mile EV has a 7.8 kW onboard inverter, and needs ~11.6 kWh to restore 40 miles.
Level 2 EVSE supply power of 7.8 kW or greater will restore 40 miles in ~1.5 hours.
EVSE with supply power above 7.8 kW will not improve charging speed, and lower supply power will take longer.
Public AC Level 2 charging stations would have more dwell time, but less turnover.
DC Fast Charge (DCFC)
Direct current (DC) electricity is directly supplied to the EV battery at 480 volts from a dispenser.
The inverter is located off-board the vehicle, in the EVSE, where AC is converted to DC.
A 350 kW DCFC restores 11.6 kWh in ~2 minutes, or 50 kWh in ~8 minutes.
50 kWh restores ~172 miles to a 0.29 kWh/mile EV.
Though charging speeds are much faster than Level 2, DCFC is not recommended for daily use, as this might shorten the life of the EV battery.
Public DCFC stations would have more turnover, but less dwell time.
Most EV charging takes place at home with Level 1 or 2 EVSE.
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AC Level 1 charging is the slowest of the 3 options, therefore many residences will want a 240 volt outlet for an AC Level 2 charger (hard-wired or plug in).
Eventually, most residences will have a 240 volt outlet for EV charging, just like most homes now have a dedicated 240 volt outlet for electric dryers or stoves.
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DCFC is not really an option for most homes, but may be appropriate for large multi-family apartment complexes.
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AC Level 2 and DCFC each have an important role to play in meeting the needs of EV drivers at public charging locations.