Electric vehicle charging stations are getting smarter and charging faster

Although electric vehicles (EVs) are not new to the marketplace (they’ve actually existed for over a century), their adoption has been particularly slow. Advancements in battery technology, along with policy regulations that support alternative energy sources for transportation, have accelerated adoption. But EVs still face stiff competition from a broad network of gas stations that can pump fuel into traditional internal-combustion vehicles virtually instantly, compared to the few hours of charging required to achieve a full charge in an electric vehicle.

EV chargers are broadly classified into three categories, Level 1, 2 and 3 chargers based on their power and charging capabilities (see Table 1). These three types can be further classified into alternating current (AC) chargers and direct current (DC) chargers based on charging technology. Level 1 AC chargers employ a slow rate of charging, using low battery-charge currents to avoid damaging the battery cells; a slow charging rate also facilitates alignment with the energy capacity of the local grid connection. Level 2 AC chargers, typically located at public charge stations, tap into the higher current connections available in commercial buildings. Technology innovations in power-handling capabilities and cell topology have led to the advent of Level 3 DC chargers. A Level 3 charger contains its own high-voltage AC/DC power supply, bypassing the on-board charger (AC/DC) on the vehicle to provide very high power charge levels.

Table 1: Electric Vehicle Service Equipment (EVSE) Type classification

Although Level 3 chargers have relatively faster charging times compared to Level 1 &2 chargers (as seen in Table 1), the former makes up for less than 10% of the total deployments worldwide. Such extended charging time (Level 3 chargers included) has been a major deterrent in adoption of electric vehicles. Adding remote monitoring and control capabilities to EVSE can help alleviate the inconvenience caused to EV owners from such extended charging times. For example, being able to remotely monitor and reserve a slot with EVSEs in the office parking lot, or at a public charging station in a mall or a freeway (see Figure 1) can eliminate the uncertainty associated with finding an EV charger at your next stop. Automatic text message when an EV charging is complete can ensure that the user makes space for the next user without added delay. Being able to automate the charging times & conditions for your EV when it’s plugged in at home would allow for EV to be charged during off peak hours when the grid tariff is lower. 

Figure 1: Use cases with remote monitoring and control of EVSE.

TI’s new Wi-Fi Enabled Electric Vehicle Service Equipment Reference Design (TIDC-EVSE-WiFi) is a perfect fit to meet the remote monitoring and control requirements discussed in the use cases above (and many more). Adding Wi-Fi to EVSE allows for monitoring of the EVSE from any Wi-Fi connected device by a standard web browser. Some of the primary functionalities included in this design are:

  • Level 1 and Level 2 charger operation (120V to 240V).
  • Power delivery up to 30A (expandable by using larger relays).
  • Pilot signal-wire communication support.
  • Latched-relay detection.
  • High-precision energy metering.
  • Communication enabled using SimpleLink™ technology over a Wi-Fi transceiver.

This reference design is the latest addition to TI’s portfolio of TI Designs that are aiding engineers develop equipment that accelerate the adoption of Electric Vehicles into mainstream markets. Later in 2016 TI plans to introduce a Level 3 EV DC charger reference design scalable up to 600 V and 400 A. Be sure to check out this space in the coming months for details on this new Level 3 EVSE power sub-system design.

Additional resources

Figure 2: Reference design board of TI's new Wi-Fi enabled Level 1 and Level 2 EVSE design.