New standard for electric vehicle chargers: touch display, reliability and durability are key

Governments around the world are actively promoting the increase in the number of electric vehicles (EVs) on the road to replace internal combustion engine (ICE) vehicles. According to the International Energy Agency (IEA), the global electric vehicle fleet will expand to nearly 350 million by 2030. For these vehicles to provide maximum utility to their owners, a charging infrastructure equivalent to the number of existing gas stations is needed. For example, the United States plans to install a network of 1.2 million public chargers by 2030.

While home chargers may require only the simplest of user interfaces, public chargers are increasingly integrating touch-enabled human-machine interfaces (HMIs). A touchscreen-based HMI allows users to select a type (subscriber or guest), choose a charging cable type, complete payment, display charging status, select a price plan, start/stop charging, and even view ads. Modern consumers prefer the convenience and speed of touch-based HMIs on chargers over signal-dependent mobile phone apps, similar to the widely accepted displays at gas stations or parking meters. Given that public chargers are primarily installed outdoors, they must meet a variety of demanding requirements, such as extreme temperatures, exposure to dust/humidity, severe weather, and protection from vandalism, while still providing a smooth touch experience. Choosing a good touch controller can take the charger's HMI design to the next level.

Advantages of touch HMI

Many charger manufacturers have decided to add touchscreens to their charger portfolio to differentiate the charging experience of their products. Touchscreens are convenient and allow charging point operators to provide a seamless experience to their customers, regardless of the phone’s battery status or signal strength. This makes them a safe fallback option for operators.

Appeal to early adopters: Feedback from the initial charger rollout shows that most early EV adopters are still young people. Chargers with aesthetically pleasing design and cool looks significantly influence the choice of charger. In fact, with the increasing number of futuristic EV designs, the design of the accompanying charger is increasingly becoming a major selling point to attract consumers (see Figure 1).

Figure 1: Comparison of old and modern charger designs

Smooth Charging Experience: Although EV charging has been around for some time, it is still a new technology experience for most consumers. Unlike gas stations, chargers are often not as intuitive or quick to operate. Today, fast chargers take 20 minutes to an hour to charge to 80% of battery capacity, while refueling only takes a few minutes. Instructional videos or step-by-step instructions can be used to teach new users how to use the terminal to charge. Once charging begins, the display can show charging status data such as battery status, remaining time, next available charger, weather information, and efficient driving tips for that battery type and vehicle model. A Frequently Asked Questions (FAQ) section required by local regulations can also be helpful. When a charger malfunctions, the display can be used to troubleshoot, provide data to the support team, and even force charging to stop to free up the cable.

Transparent pricing and receipts: Like gas prices, the price of the app’s charging is displayed to users to incentivize them to use the provider’s network and subscribe to a permanent membership. By initially selecting the user type (guest or member), operators can offer users different payment plans and payment models. Business users can enter their email address to get a receipt for their expense claims.

Choice of payment mode: In fact, non-member users should be able to pay for charging without being forced to subscribe to the charger network mobile app. This helps to increase the customer base of charging point operators. Therefore, the payment option of accepting credit cards through RFID NFC readers and entering a PIN on the touch screen can also be selected. This payment system is particularly important when payment through the app is not possible due to a dead phone battery or unavailability of the Internet. Feedback shows that users do not want to download a new app at a new location, register a new online account and add a credit card for verification in order to pay, especially in remote places with poor signal such as underground parking lots or highways.

Figure 2: Easy payment via touch screen

In fact, regulations such as the European Union (EU) Alternative Fuels Infrastructure Regulation (AFIR) have made it mandatory to use credit card payments on electric vehicle chargers. This means that the HMI systems used on chargers need to comply with the Payment Card Industry (PCI) standards. Therefore, touch displays and their controllers have more stringent requirements, and both need to be high-performance components that can provide end users with a comfortable and safe charging and payment experience.

Additional revenue for retailers: Displaying advertisements on charger touch screens in mall or supermarket parking lots can provide retailers with an additional revenue stream.

Language selection: Charger manufacturers can cover a wider range of geographies by offering the charging experience in different languages. This way, users traveling to different locations, such as the European Union, will be able to use the charger seamlessly.

Challenges of Outdoor HMI Systems

To ensure that outdoor HMI displays operate successfully over their expected long service life, several operational issues must be addressed during the design phase to avoid repeated repairs, failures, and field replacements. While most of these issues are specific to the display design and its physical integration into the enclosure, choosing an excellent touch controller can help them reach their full potential and save future costs. Common scenarios that can impact touchscreen display design include:

Rain: Charger housing assembly requirements usually meet IP65 waterproof and IP68 waterproof and dustproof levels. The touch controller should not detect water drops as false touches, but only detect real finger/glove touches.

Sunlight heat/UV exposure: The display needs to be readable in sunlight at 2,000 to 3,000 nits (compared to 1,000 to 1,500 nits for standard displays). Anti-reflective and anti-glare coatings on the glass can be used to improve readability. The additional use of an ultraviolet (UV) filter can reduce screen damage, such as color shifting and fading in some extreme cases. An infrared filter protects the display from infrared radiation and prevents heat buildup. However, the thicker the display stack, the more difficult it is for the touch controller to detect valid touches.

Extremely cold or hot temperatures : The charger can be used in any country in the world. While heating or cooling elements can be integrated into the display to keep it within normal temperature ranges, the touch controller also needs to meet automotive/industrial standards to operate properly within the same temperature range.

Thick gloves: Thick gloves are often used in cold weather, but can also be used in rainy conditions. The touch controller needs to support complex interactions with the additional layer of glove material on the surface. For example, if there is a map on the screen showing the next available charger, multi-finger zooming must be supported in wet conditions regardless of whether the user is wearing gloves.

Vandalism: To minimize the risk of vandalism, displays are typically made of 5mm to 6mm thick IK10-type (hammer-resistant) glass or 2mm to 3mm thick plastic PMMA. Vandalism testing specifications may vary depending on the installation location and model of the EV charger, but the touch controller needs to detect finger touches through this thick glass, including when wearing gloves and even with raindrops on the glass. In addition, an air gap can be used between the screen and the glass so that in the event of vandalism, only the glass unit can be replaced instead of the entire display. This further increases the thickness, making it even more difficult for the touch controller to detect the touch.

Credit card payments: As mentioned above, a payment method can be built into the charger. This could be a credit card reader module with a mechanical keyboard. In this case, there are no special requirements for the touch controller. However, if a near-field communication (NFC) contactless reader is also provided and the user can set an amount or enter a PIN via the display, the touch controller needs to encrypt the PIN transmission to comply with PCI certification requirements in the EU, UK, and other regions.

Harsh cleaning: If someone uses bleach or other chemical liquids to clean the display, then this should not affect the display or touch performance. The touch controller needs to be able to cope with a wide range of conductive liquids and should not detect them as touches.

Simply replace your display with a high-performance touch controller to take it to the next level.

Microchip's maXTouch® family of touch controllers offers a range of features to address these stringent outdoor requirements and optimize the touch experience on displays. The devices support:

• Various screen sizes (approximately 2-inch to 34-inch displays) and aspect ratios

• Very high conducted noise immunity (IEC 61000-4-6 Class A certified)

• Cover glass up to 10 mm thick

• Air gap of 0.2 mm or more

• Thick gloves with multiple fingers (up to 5 mm thick, such as winter ski gloves or motorcycle gloves)

• Moisture resistant to dripping and running water