Navigating Wireless Technology Options and Antenna Considerations for EV Charging Stations

EV chargers are used in a wide variety of public and private installations, from charging stations at malls and travel stops to fleet charging depots at truck terminals and logistics parks. Wireless plays a fundamental role in all of those by providing network connectivity for remote diagnostics, transaction time stamping, HD map downloads for autonomous vehicles, and more.

For example, wireless helps charging network operators ensure that their chargers work. This is a chronic problem that frustrates EV owners. A University of California study of public chargers in the Bay Area found that only 72.5% were functioning.

A wireless network connection enables operators to remotely monitor and troubleshoot their chargers — and sometimes even repair them, such as when a reboot or patch is all that’s required. These remote capabilities directly affect the bottom line by avoiding lost business. They also ensure that chargers funded by the U.S. National Electric Vehicle Infrastructure (NEVI) Formula Program can meet the 97% uptime requirement

Read on to learn more about how GNSS, cellular, and Wi-Fi enable those applications and what to consider when choosing an antenna for each type.

GNSS

EV charging stations don’t move because they’re bolted to concrete, but they still rely on GNSS for timing applications such as time stamping payment transactions. A patch antenna is a good choice for several reasons:

• Patches work best when they have a clear view of the sky, an orientation that’s easy to ensure with a permanently mounted device.
• They support circular polarization, which is ideal for receiving circularly polarized GNSS signals.
• Their high gain and stable phase center help maximize performance, which helps maximize the performance and reliability of the applications using GNSS.

(For a deeper dive into gain, polarization, and other attributes that directly affect GNSS timing performance, see “Right on Time: Understanding GNSS Timing Fundamentals.”)

GNSS’ positioning capabilities can help facilitate the charging process. An example is public transit buses that use an overhead pantograph to charge. Differential GNSS (DGNSS) positioning techniques such Real-Time Kinematics (RTK) can achieve precision as low as 1 centimeter. This precision location information enables the bus’s advanced driver-assistance system (ADAS) to guide a successful docked with the pantograph. This eliminates damage that occurs as drivers run into other objects while trying to maneuver into place. (For more insights into using DGNSS, see “Attention to Detail: Leveraging Real-Time Kinematic (RTK) Technology to Maximize GNSS Precision.”)

Whether it’s used for positioning, timing, or both, the GNSS antenna must be designed to withstand years of exposure to the elements. Look for models whose enclosure is IP67 rated and UV resistant, which are key for protecting the antenna from environmental damage from storms and sunlight.

If the charging station isn’t under a canopy, lightning is another potential risk. Look for models with IEC 61000-4-5/Class 4 surge protection, such as the Taoglas Bolt A.93.A. Even birds can be an issue. To thwart perching, which blocks signals, choose an enclosure style or installation location that’s uncomfortable or inconvenient.

Cellular

4G and 5G are convenient ways to provide charging stations with broadband connectivity. Cellular eliminates the need to pull an Ethernet cable, which might not even be an option in many locations. An example is U.S. government initiatives to build public EV charging stations on interstates to mitigate the range anxiety that is one of the major reasons why vehicle owners stick with ICE models. Cellular often is the only telecom network available in remote locations such as rural highway rest stops.

Unless the charger is bundled with a wireless plan, it’s impossible to predict which mobile operator will provide service once it’s installed. This means the antenna’s band requirements will be determined by the ones that the cellular module supports. But some tips and best practices apply across the board, regardless of band, operator, and cellular generation. To maximize performance and reliability, see:

• “Four Top Reasons Your GNSS and Cellular Antenna Performance is Suffering”
• “Understanding Antenna Spatial Diversity and How It Affects Device Performance”
• “How to Choose the Right Cellular Antenna Type for Your Application”
• “Enhancing Connectivity: The Role of Multi-Band Cellular Antennas in Expanding Network Coverage”

When using cellular, it’s important to ensure that it co-exists peacefully with the charger’s GNSS system. For the GNSS antenna, focus on specs for out-of-band rejection. For example, at the commonly used LTE frequencies between 700 MHz and 1 GHz, the Taoglas Bolt A.93.A provides greater than 80 dB of rejection. Between 1820 MHz and 3500 MHz, it has greater than 60 dB of rejection. This ensures that timing performance isn’t compromised when the GNSS antenna is installed near the charger’s LTE transmitter and antenna. The same advice applies if the charger uses Wi-Fi in addition to, or in lieu of, cellular.

Wi-Fi® 

Wi-Fi is another option for providing network connectivity. For example, if a logistics park or travel stop already has extensive outdoor Wi-Fi coverage, that could be the primary network or the fallback/redundant network to cellular.

Wi-Fi also can be used for vehicle-charger communications. For example, fully autonomous EVs need high-resolution maps, and charging is an ideal time to download the set for the next leg of their route. These map files are enormous because the use case requires high resolution to help ensure safety. This is best done over Wi-Fi while the vehicle is charging rather than using cellular, which would incur fees.

Another potential application is using Wi-Fi to collect telematics data from the vehicle while it’s charging. Regardless of whether the vehicle is autonomous or has a driver behind the wheel, the ability to collect data about its health is key for identifying emerging problems before they escalate into extensive, expensive repairs and downtime. This collection can be done over cellular while the vehicle is on the road, but using Wi-Fi at the charger eliminates mobile fees.

Get in touch for orders or any queries: sales@rfdesign.co.za / +27 21 555 8400

Courtesy of Taoglas