The number one question people ask me about EV charging is ‘Is there a standard plug?’, closely followed by ‘How long does it take to charge a car?’
There are four ideas that answer these two questions.
First, there is a worldwide standard for the plug to charge any EV. It’s called an SAE J1772. From the Society of Automobile Engineers, the plug is designed to fit any car and create a connection between a ESEV and the car. It has been engineered for safety in dry or wet conditions and has internal checks and balances before it all allows communications and power to flow from a source to a vehicle.
Second, The plug can transmit energy between EVSE operating at either 110 volts (known in the industry as a L1 charge) or at 220 volts (an L2).
Third, each car has a battery of a different size. Battery size, or capacity, is measured in kilowatt hours (kWh). Battery capacity for electric vehicles will range from as little as 3 kWh to as large as 40 kWh or more.
Fourth, the amount of time to fully charge an EV battery is a function of the charger type (L1 or L2) the battery capacity of the vehicle and the charger in the vehicle. How fast you can charge depends on the size of the charger on the car.
In the simplest terms, a charging station is an outdoor power outlet, just like any 110V or 220V in your home. It provides electric current from the grid to your electric vehicle’s on-board charger. The charger on the car is what converts alternating current from the grid into direct current to recharge the vehicle’s batteries, doing so in a controlled manner that doesn’t damage them.
A modern charging station does have some intelligence built into it. For security reasons, it can restrict access to those authorized to use it. It can meter how much energy is used, when and for how long. It can detect system faults and respond accordingly; and it can provide voltages from 110V to 230V: what are considered Level 1 and Level 2 charging, respectively.
What they don’t do, however, is control how the batteries on the vehicle are charged. That is up to the charger on the vehicle, itself, and its battery management system. The process of properly charging a battery to insure its longevity is a complex one dependent on battery chemistries and how the pack is engineered. Think of a charging station as a water spigot on the side of your house. It regulates the flow of current through the ‘hose’, but how that water is dispensed depends what’s at the other end of that hose. It can come out as a ground-soaking torrent or a gentle mist. Batteries prefer the latter, electrically speaking.
It will take a car like the Leaf 20 hours to charge using an L1 charging system and about 8 hours using a L2 charging system. For a car like the BMW Active E, which has a bigger battery and a bigger on-board charger is will take about 14 hours to charge using L1 and about 4 hours to charge using L2.