Charging for Electric Vehicles: How It Works?
2021/12/31 By hqt
For those who are just starting to get acquainted with this topic, it may seem that charging for an electric car is something like charging a phone. It's actually a complex ecosystem.
Now the charging market has formed three segments: home, private and public. 60% of charging now is home use when users install the charger at home, and if possible, in the parking lot of their apartment building.
Private chargers are chargers from private companies. For example, a bank installs chargers for its employees who have their own electric vehicles.
Public chargers are available to everyone, they are located in cities and along highways.
How do these three segments differ - home, private and public?
Let's start with the home segment, where hardware can be simpler in terms of hardware. These are the so-called second-level charges. The owner of such a charge does not need to somehow specifically distribute access to the pistol. The main task is to charge your car, and the statistics, which then come to your smartphone, are no longer so important.
Integration with the smart grid, of course, complicates the simplest charging option: a connection to the server is required, and the server itself is connected to the electricity supplier - this is how the maximum charging current is controlled at different times. This is an interesting engineering challenge, but there are even more interesting projects.
What is charging from the point of view of iron, hardware filling?
There are three charging levels. Charges of the first level are really similar to chargers for a phone: we plug in any socket for 110-120 volts, 6-8 amperes.
The second level (the most common) requires 220-240 volts with an alternating current of 30 amps maximum. A car with such a charge takes from 6 to 30 amperes.
Consider what is inside the charger for home use:
- power converter board (GFCI), which converts voltage, it has built-in different types of protection;
- a board for monitoring communication with a car, often an analog interface is used in chargers of this level (a signal called a pilot signal is used for communication);
- communication board, which can have its own modem with wi-fi or cable.
Chargers for private and public use additionally contain built-in protection for restricting access and screens for communicating with the user. They can also have a controller for integration into a building management system.
Chargers of the third level for offices and public places are such large "refrigerators" along the highway, in big cities and at gas stations. They are quite complex technologically: 100-150 kilowatts, hundreds of amperes, 480 volts. These are devices with constant current, the so-called DC-charging. It takes 10 to 30 minutes maximum to fully charge the car.
A distinctive component of DC chargers is an additional power module for current conversion and control. And when it comes to hundreds of amps, the charging cable itself is quite heavy, not everyone has the strength to plug it in.
From the point of view of communication, the charges of the second and third levels are similar - they use the same modems to connect the charging to the server. Modems in old models can no longer support the required speed and the amount of data that is transferred from charging to the server.
Why are old modems no longer enough for data transmission? How does the volume of this data grow?
Let's take public chargers as an example: they can be set for a simple hourly rate, or it can be dynamic, taking into account a discount depending on the consumed electricity, time of day or promotions of specific car manufacturers. Accordingly, the complexity of communication also increases.
What interfaces for data transmission are used most often and why?
There are two types of interface used: between charging and modem + between modem and server. And the modems themselves are built-in and external.
External modems are mainly used for private and public solutions when you need to connect many chargers to one modem.
The interfaces between the charger and the modem are often wi-fi or ZigBee. ZigBee is the most efficient, but its bandwidth is the same as that of wi-fi, and it is not always sufficient. Wi-fi is simpler, but not always convenient for installation in public places (on the streets or in parking lots, where the signal quality is not always good).
And now about the infrastructure: what is the difference between refueling for electric vehicles and refueling for conventional cars with a gasoline engine?
To charge an electric car, you can use an additional application and indicate the type of your car in it. Such an application will tell you how to plan a route, where to charge and how much it will cost. And each of these services - logistics, integration with payments - are separate engineering tasks.