EV Charging Guide

Overview

To get the most out of the EV charging experience it is important to be aware of a few concepts that determine the rate at which a battery can recharge. Read below for the details, and, as always, feel free to contact us for additional information.

Battery Pack Rating

EV's have a battery pack with a specific capacity available to store a charge. This capacity is measure in kilowatt hours (kWh). The greater the battery pack's kWh rating, the greater the distance that the EV can potentially travel before the battery is fully discharged.

Power Acceptance Rate

EV's have a charger on-board the vehicle that converts the alternating current (AC) delivered by the charging station to direct current (DC) so that the battery pack can be recharged. On-board chargers have a maximum power acceptance rate, measured in kilowatts (kW), that determines how fast the battery can accept electricity while recharging. The higher the rate the faster the battery can be recharged. The power acceptance rates for popular EV's today range from 3.3 kW (Chevy Volt) to 10 kW (Telsa Model S).

Power Delivery Rating

Charging stations safely deliver electricity from the power source to the EV's on-board charger. These devices have a power delivery rating, measured in kilowatts (kW), that determines how fast the electricity can be delivered to the on-board charger. This rating is based on the charging station's volts and amps measurements.


Volts

Charging stations are identified by levels based on the voltage of their power source. Chargers that connect to a 120 volt AC source are classified as level 1 charging stations and chargers that connect to a 240 volt AC source are classified as level 2 charging stations. There are also chargers that connect to 480 volt DC sources that are classified as level 3 charging stations, or DC fast chargers. The greater the voltage of the source, the greater potential for the power delivery rating of the charging station.


Amps

Another factor that determines the charging station's power delivery rating is the amount of amps the device draws. This is a measurement of the flow of electricity.


Calculating Power Delivery

The product of a charging station's volts and amps determines the power delivery rating.  For a 240 volt 32 amp charging station the rating is calculated as follows: 240 * 32 = 7,680 watts = 7.68 kW.

Estimating Charging Times

Estimates of charging times are calculated by dividing the EV's battery pack rating by either the power acceptance rate or the power delivery rating, whichever number is smaller.  The component with the smaller number limits the speed at which the EV's battery can be recharged.  

For example, a Chevy Bolt has a battery pack rating of 60 kWh and a power acceptance rate of 7.2 kW. When comparing a level 1 and level 2 charging station, the estimated charging times are limited by different components:

  • Level 1: 60 (battery pack rating) /  1.4 (power delivery rating) = 43 hours
  • Level 2: 60 (battery pack rating) / 7.2 (power acceptance rate) = 8 hours

View the file below for a list of EV's and a comparison between their estimated level 1 and level 2 charging times. 

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150 S Elizabeth St, Rochester Michigan, 48307, United States

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