For efficient wireless charging of electric vehicles (EVs), many believe it’s sufficient to align the charging pads in close proximity. However, wireless communication between the EV and the charging station is equally vital for successful wireless EV charging. This FAQ walks you through how a wireless communication network (IEEE 802.11n) can be used for the wireless charging of EVs.
A wireless network protocol is necessary for front-end communication during EV charging and communication. Front-end communication refers to monitoring and controlling the EV charging process directly between the vehicle and the charging station. Back-end communication happens between the EV charging station and one’s home, the electric grid, and cloud services.
Figure 1 demonstrates the wireless network protocol involved during the wireless charging of an EV and the wireless power transfer occurring at the bottom of the vehicle. The IEEE 802.11n Wi-Fi standard is referred to as the wireless network protocol and is an example of front-end communication.
The supply equipment communication controller (SECC) and electric vehicle communication controller (EVCC) are the nodal points for communication during EV wireless power transfer. This communication has multiple functions, including checking the proper alignment of power coils, the status of the battery charge, detecting faults, and others.
To understand how Wi-Fi 802.11n can help in the complete wireless charging process, see Figure 2.
In stage 1, the Wi-Fi network identifies if an EV is approaching the supply equipment for charging. The connection between the SECC and the EVSS is established first, signifying that the charging process will begin.
Stage 2 allows fine positioning of the wireless charging pad between the EV and the supply equipment. This occurs in two ways. The centers of the wireless charging pads must be aligned and in close proximity to the pads. Both are necessary for efficient EV charging.
Stage 3 is when the connections for wireless power transfer are prepared and finalized. At this point, the Wi-Fi network can also select a suitable frequency bandwidth, typically between 2.4 and 5 GHz, for proper communication.
Wi-Fi 802.11n, also known as Wi-Fi 4, supports both bandwidths, but 2.4 GHz is preferred (5 GHz is an optional feature in Wi-Fi 4).However, Wi-Fi 5 and later have the desired frequency bandwidth of 5 GHz with optional support for 2.4 GHz. Many commercially available devices support Wi-Fi 4 because of its better signal strength. Therefore, 802.11n is preferred for home and commercial wireless EV charging.
Stages 4, 5, and 6 are meant for connection, charging, and disconnection, respectively. During these stages, the wireless charging pads of the supply equipment may be raised above the ground and closer to the charging pad of the EV.
As the coupling coefficient of the wireless charging network is increased, the maximum power transferred from the supply equipment to the EV also increases proportionately. When the connection is active during stage 5, the supply equipment continuously monitors the EV battery’s various parameters — including state-of-charge, temperature, and cell voltage balances, through the wireless network.
Even though the charging process ends at stage 6, the supply equipment should be notified of the EV exit and prepared for the next charge. Such communication can happen only through a wireless connection, and Wi-Fi 802.11n has sufficient signal strength and data transfer rate to do so.
This FAQ discussed the often underrated information related to wireless communication and charging for EVs. The power transfer and communication exchange are equally significant for a successful EV charging process. It will be interesting to see how the Wi-Fi 5 (and later) standards are used for wireless EV charging.
- Experimental Implementation of a Wireless Communication System for Electric Vehicle WPT Charger, E3S Web of Conferences
- Future-proofing EV charging solutions with wireless connectivity, ublox
- Wireless Charging, E-Mobility Engineering
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