How to Code Your Own Electric Vehicle Charging Station Management System

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Designing Electric Vehicle Battery Charging Solutions

The popularity of electric vehicles (EVs) is increasing rapidly in India. According to a survey, the EV market in India is estimated to increase from 3 million units in 2019 to 29 million units by 2027 with a CAGR of 21.1%. As a result, demand for AC/DC chargers and smart EV chargers will also increase.

In order to charge the batteries efficiently and to ensure their long life, we need smart battery management or charging system. To realize such EV charging stations, Holtek has come up with smart Electric Vehicle Battery Charging Solutions based on their low-cost ASSP flash microcontroller (MCU) HT45F5Q-X for charging EV batteries.

At present, three EV charger designs suitable for the Indian market with specifications of 48V/4A, 48V/12A, and 48V/15A are available for rapid development of the product. This semiconductor-based smart charging system can support both lithium-ion as well as lead-acid battery types.

EV Charger Block Diagram

The Block diagram of the Electric Vehicle Battery Charging Solution is shown in Fig. 1. Here, battery charger ASSP flash MCU HT45F5Q-X is the heart of the EV charger circuit with in-built operational amplifiers (OPAs) and digital-to-analog converters (DACs) that are necessary for battery charging function.

Designers can choose an appropriate MCU from the HT45F5Q-X series according to their application requirements.

Specifications of the battery charger flash MCU HT45F5Q-X series are shown in Fig. 2.

The features and working of the EV charger solution for 48V/12A specification are briefly explained below. This EV charger design utilizes HT45F5Q-2 MCU for implementing the battery charging control function.

The MCU incorporates a battery charging module, which can be utilized for closed-loop charging control with constant voltage and constant current for efficiently charging a battery. The internal block diagram of MCU HT45F5Q-2 is shown in Fig. 3.

The battery charging module in HT45F5Q-2 has built-in OPAs and DACs that are needed for the charging process. Therefore the design reduces the need for external components like shunt regulators, OPAs, and DACs, which are commonly used in conventional battery charging circuits. As a result, the peripheral circuit is compact and simple, resulting in a smaller PCB area and a low overall cost.

EV Charger Working

Input power to the EV charger is an AC voltage in the range of 170V to 300V. The EV charger uses a half-bridge LLC resonant converter design, because of its high-power and high-efficiency characteristics, to obtain DC power for charging the battery.

The design utilizes a rectifier circuit for converting input AC voltage to high-voltage DC output, and it also has an electromagnetic interference (EMI) filter to eliminate high-frequency noise from the input power source. A pulse-width modulation (PWM) controller IC, like UC3525, can be used for driving the MOSFETs of the half-bridge LLC converter.

The battery charging process is supervised by the MCU HT45F5Q-2. It monitors the battery voltage and charging current levels and gives feedback to the PWM controller IC. Based on the feedback, the PWM controller varies the duty cycle of its PWM signal and drives the MOSFET circuit to obtain variable output voltage and current for charging the battery.

For better protection, HT45F5Q-2 is isolated from the rest of the circuit (i.e. high-voltage components) using a photo-coupler. Battery-level LED indicators are provided for knowing the charging status.

EV Battery Charging Process

The change in charging voltage and current during the charging process is graphically illustrated in Fig. 4. If the battery voltage is too low when connected for charging, low charging current (i.e. trickle charge (TC)) will be set initially, and the charging process will start.

When the battery voltage increases to a pre-defined level (Vu), constant voltage (CV) and constant current (CC) are applied for charging and continued until the battery is fully charged. The battery is considered to be fully charged when the voltage reaches VOFF. When the charging current drops to Iu, the final voltage (FV) is set.

The voltage, current, and temperature control processes in this EV charger are explained below.

(a) Voltage Control

The charging voltage is decided based on the initial voltage of the battery when it is connected for charging. As the charging progresses, the charging voltage changes accordingly, and finally, when the battery is fully charged, the final voltage is set. The charging-voltage decision levels for the 48V/12A battery charger are explained below.

• If Battery Voltage <36V, TC(0.6A) Charging, Voltage Setting FV(56V)
• If Battery Voltage <40V, TC(0.6A) Charging, Voltage Setting CV(58V)
• If Battery Voltage >40V, CC(12.0A) Charging, Voltage Setting CV(58V)
• When fully charged, the voltage is set to FV(56V). If the battery voltage is lower than FV, the charging current will be reset to CC (12.0A).

(b) Current Control

The charging current is set depending on the battery voltage. Initially, if the battery voltage is too less, a trickle-charge current would be set for charging the battery. Once the battery voltage reaches a certain level, a constant current is supplied for charging, until the battery is charged fully. The charging-current decision levels for the 48V/12A battery charger are listed below.

• Recharging Current <1.2A, determine the end of charging
• Recharging Current >0.2A, determine the start of charging

(c) Over-temperature Protection

The EV charger has a negative temperature coefficient (NTC) thermistor to monitor the temperature and a fan to regulate the heat. When the temperature increases, the fan is automatically switched on to dissipate the heat; it gets switched off when the temperature is reduced to the lower set threshold. Also, the fan turns on when the charging current is high and turns off when the charging current is low.

• When NTC temperature >110C, the charging current will be reduced to 50% of the charging current and will be monitored periodically

(d) LED Indications for Charging Status

These are listed below-

• TC charge, red light flashes slowly (0.3 sec on, 0.3 sec off)
• CC, CV charge, red light flashes quickly (0.1 sec on, 0.1 sec off)
• When not charging, the green light is on
• When charging time exceeds eight hours, red and green lights are bright

(e) Charging Duration

When the charging duration is exceeded (duration depends on battery capacity), the voltage drops to FV, the current is reduced to TC, and the charger repeatedly monitors the battery voltage.

EV Charger Circuit Diagram

The schematic of the Holtek EV charger design for 48V/12A type is shown in Fig. 5 for reference and its PCB assembly is shown in Fig. 6.

Check High-Resolution Image

The ASSP flash MCU HT45F5Q-2 can also be used for designing higher-wattage solutions. It offers a programmable option for setting parameter thresholds, which makes it very convenient for EV charger designs. Holtek provides technical resources such as block diagrams, application circuits, PCB files, source code, etc. to help designers in rapid product development and speed up time-to-market.

EV charger development platform for the HT45F5Q-X series will also be available soon. Using this software tool, users would be able to easily select the charging voltage/current and other parameters to create a program. This application will also be able to generate a program containing a standard charging process, thereby significantly simplifying the development process.

Krishna Chaitanya Kamasani is the director India operations at Holtek Semiconductor

The complete guide to starting an EV charging station business

Vehicle electrification is a small but mighty step in addressing the climate crisis. The recent surge in EV sales is encouraging, but all those vehicles need chargingand we have a ways to go before charging stations become as accessible as gas stops. Fortunately, savvy businesspeople around the globe want to help. Theyre wondering how to start an EV charging station business in ever-increasing numbers.

This comprehensive guide will take you through the process, shedding light on the necessary market research, popular business models, grant opportunities, technical and regulatory standards, and more youll face in the course of business. Equipped with this info, your business will be up and running faster than a DC charger fills a battery.

Funding your EV charging station business

When investigating how to start an EV charging station business, grants stand out as an attractive inroad. It's important to consider each carefully, making note of hard deadlines, explicit program goals, desired outcomes, and guidance about how the funds can be used.

Grant opportunities

President Biden's Bipartisan Infrastructure Law carved out billions in federal funding for infrastructure for electric and hydrogen-powered vehicles. These grants, offered by the US Department of Transportation, can provide a minimum of $500,000 in funding, but take note: The funding must go toward rural communities of less than 10,000 people. These areas likely have next-to-no competition, which could give you an early foothold in expanding markets.

Volkswagen's Diesel Emissions Environmental Mitigation Trust came out of the company's emissions scandal as an effort to undo some of the damage it caused. The trust as a whole creates grant opportunities for projects encouraging the adoption of sustainable transportation, and a portion of it is dedicated specifically to developing EV charging infrastructure in the US. The National Association of State Energy Officials (NASEO) has general info about grant opportunities, but applicants need to check their state's website for specific requirements, as the trust allocates funding at the state level.

Speaking of the state level, several have their own funding offerings. California's Clean Transportation Program offers a mix of grants, contracts, and rebates for EV charging infrastructure, among other sustainable transportation solutions. New York's ChargeNY initiative targets EV charging, specifically. With Charge Ahead Colorado, that state offers grants for the installation of Level 2 and Level 3 fast charging stations in public and private locations. Be sure to check for funding opportunities in your state.

A great starting point in Canada is the Zero Emission Vehicle Infrastructure Program. This $680 million program has carved out funding for EV chargers across the country, but competition is stiff. To be eligible, your proposal must include at least one charger of 200 kW and above, two fast chargers of 50 kW and above, or 20 chargers of all charging levels. Check out our ZEVIP resources page for more info.

For more funding opportunities for your electric vehicle charging station business, read 7 EV charging station grants to apply for when starting your EV business.

Choosing a business model

There are a few common models those wondering how to start an EV charging station business typically consider. The right one for you will vary according to your goals, expertise, and available resources.

Charging network

Charging networks work like gas station chains. In this model, you'll own stations at several locations to maximize market density. By charging EV drivers flat or variable rates based on fluctuations in power supply, you'll bring in revenue. You'll either operate the stations yourself or pay a service to maintain them.

This model is very time and resource-intensive because it demands an upfront investment in infrastructure in addition to ongoing maintenance (which in turn demands expertise). It makes the most sense for gas station chains that want to move into the EV space.

Solutions provider

Rather than provide the charging infrastructure, solutions providers sell EV hardware, software, and services to residences, commercial buildings, fleet operators, and more. Their offerings vary, including consultation, maintenance, turnkey services for businesses looking to provide EV amenities, and more. Payment occurs either at installation, monthly, or annually if service is ongoing. In this model, turning a profit means soliciting discounts on hardware and software you then sell at a markup. Strong sales and customer service skills are vital to this model, and experience with EVs or other green tech can be a boon.

To learn more about how to start an EV charging station business with a model that works for you, read How to develop a profitable EV charging station business model.

Maintenance considerations for an electric vehicle charging station business

Operating a successful electric vehicle charging station business means ensuring every piece of the operation stays in working order. That keeps customers happy and revenue flowing. As sophisticated feats of engineering, Level 2 and DC fast chargers have several components you'll need to maintain.

Hardware

The hardware components of an EV charger include its charger box, battery, switches, converters, cables, and connectors. Outer components should be checked for damage and wear on a regular basis, with supplemental checks performed after stormy weather. Connectors and cables must be cleaned of dust and other debris to ensure they work well for as long as possible.

Power management

Use your charging station management system (CSMS) to allocate safe and efficient loads for each of your chargers. The system should have safeguards in the event of lost connectivity, maintaining max charge set points in non-volatile memory. A software-driven power management system will outperform local load management features available on the hardware itself. Some systems, including ChargeLab, can detect a full vehicle battery and reallocate power to other chargers on the fly.

If your Level 2 charger takes more than a few hours to give a full charge, or your DC fast charger takes over an hour, you may have a voltage issue that requires fixing or replacing the battery.

Payment processing

EV charging stations rely on payment processing infrastructure such as RFID readers and credit card scanners to collect customer payments. Customers typically transact either via their mobile device (in-app or on the web) or through an external point-of-sale interface. Your CSMS should have complete and accurate receipt information to maintain compliance with CTEP.

Connectivity

If a charging station in your network disappears from your CSMS, that's a sure sign something needs fixing. It may be that the station itself has a hardware problem that requires repair, or it may be a simple connection problem. Choosing a CSMS provider that offers customer support can accelerate troubleshooting and safeguard against extended outages.

For more on maintenance considerations, read A guide to EV charging station maintenance.

Need-to-know EV charging station regulations

Several standards have been propagated around EV charging, handed down by hardware manufacturers, software designers, car manufacturers, and national governments. Here are two of the most important ones in the United States.

If you want to know how to start an EV charging station business safely in the US, you need to review NEC Article 625. That article sets the bar for installing and maintaining EV charging equipment, from where to put the equipment to what kind of materials to use. Some key points:

• EV charging systems can be placed indoors or outdoors as long all their physical infrastructure fits and their charging cables can reach EV charging ports. However, where you place your system will affect your ventilation, waterproofing, and shock protection needs.
• EV chargers must be stored 18 inches above the ground if indoors or 24 inches above the ground outdoors.
• EV charging systems must use cables appropriate for their location. Those cables should carry one of the following labels designating NEC approval: EV, EVJ, EVE, EVJE, EVT, or EVJT. Charging cables longer than 25 feet require a cable management system, but the standard practice is to manage shorter lines, too.

With $5 billion in federal funding available for EV charging systems, the Department of Transportation (DoT) stepped in with guidelines around who could apply for funding. Funding applicants must meet the National Electric Vehicle Infrastructure standard, which went into effect on March 30, 2023. The standard is designed to promote interconnected EV infrastructure along federal highways, but any system that uses Title 23 federal funds must meet it no matter its location. NEVI covers topics such as eligible charger types, payment processing, cybersecurity, data privacy, and labor rules.

For more on EV charging station standards, read The big list of EV charging station standards and specs to know.

The importance of universal charging stations

Universal EV charging stations are designed to let EV owners charge their cars no matter what hardware standard or software system is in place. This interoperability makes owning (and recharging) an EV simpler and more practical, which drives further adoption.

In the current EV charging station landscape, operators have to deal with several inconsistencies among different chargers. For example, the wide gamut of hardware can make it difficult to scale a charging network efficiently. But with universal charging software, operators can mix and match products from various manufacturers according to their own budgetary, market, and quality concerns to create the stack that works for them. EV drivers benefit, too, as open protocol charging frees them from painstakingly planning every charging stop on their trip.

Despite their promise, universal charging stations have yet to conquer the market. Many EV chargers claim to be universal, but drivers frequently visit charging stations that turn out to be incompatible. This makes it hard for potential EV owners to trust they can recharge when needed and complicates ownership of EV charging stations.

ChargeLab was one of the first 50 members of the Open Charge Alliance and has advocated for the adoption of open protocols in EV charging since the very beginning (in fact, we run an entire boot camp program for manufacturers to improve their OCPP compliance!).

For more on universal charging stations and the future of EVs, read How universal EV charging stations are driving EV adoption.

Critical EV charging standards

As the EV industry matures, more and more manufacturers are adhering to standards that maintain high levels of quality and consistency for consumers. Standards now exist that govern operation, installation, and safety.

Operating standards

Installation and permitting standards

• The Alternative Fuels Data Center maintains a list of installation requirements from the US government, and its permit template provides a solid framework for what to expect.
• The Americans with Disabilities Act (ADA) will apply to your electric vehicle charging station business, so be sure to review it during planning to ensure disabled customers can charge with ease. The Accessible Canada Act applies many similar requirements.

Safety and security

• SOC 2 compliance helps ensure a high standard of information security.
• PCI DSS compliance safeguards customer payment info and keeps your business in good standing with payment card companies.

To learn more about the regulations and standards that affect how to start an EV charging station business, read The big list of EV charging regulations and standards.

Charger specifications to know when starting an EV charging business

EV chargers have different specifications based on their expected charging level. There are three levels in total:

• Connection: Standard 120V outlet
• Charge speed: 5 km or 3 mi per hour of charging
• Average time to full charge: 20+ hours

Level 1 chargers are the simplest to manage because they use existing electrical infrastructure. That makes them a good fit for residential or emergency use. On the other hand, their slow charging speed disqualifies them from commercial use.

• Connection: 240V outlet
• Charge speed: 3050 km or 2030 mi per hour of charging
• Average time to full charge: 6 to 14 hours

Level 2 chargers require specialized installation, using higher-voltage outlets and dedicated software to charge faster and intelligently bill customers automatically. They're well suited to retail deployments.

• Connection: Direct current
• Charge speed: 200 km per hour or 124 mi per hour
• Average time to full charge: 20 minutes to an hour

Level 3 chargers use direct current (DC), which requires specialized hardware and electrical infrastructure. This gets them unparalleled charging speeds, making them ideal for thoroughfares and along major highways as gas station replacements.

EV connector types

Part of starting an EV charging station business means choosing which connector types to support. Some of the most popular examples include:

• SAE J1772: The North American standard, also known as the J Plug, supports Level 1 and 2 charging systems.
• IEC 62196 Type 2: The European standard supports Level 2 chargers.
• Combined Charging System (CCS): A DC connector for Level 3 charging in North America and Europe.
• CHAdeMo: A DC connector designed by the Japanese company of the same name and popular in Japan.
• GB/T: The standard connector in China, with different models for each of the three charging levels.
• NACS: A formerly proprietary connector for Tesla EVs, the North American Charging Standard is now open to the industry. Automakers, including Ford, GM, Nissan, and beyond, have announced plans to adopt the standard.

For more on installation requirements and network compatibility, read EV charger specifications every pro needs to know.

Maximizing ROI when adding EV charging to your business

As the number of EVs on the road has more than tripled in the past three years, demand for hotels, condos, and other businesses to add charging stations to their offerings has continued to mount. These chargers' return on investment (ROI) can include additional revenue, brand appeal, and cost savings with the careful deployment of EV charging incentives.

To determine your ROI, begin by understanding your customers. How safe will they feel leaving their vehicles in your care, and how quickly will they need their cars recharged? The busier your business, the more sense it makes to invest in fast Level 3, or DC, chargers. Businesses with slower customer turnover, such as hotels, can likely use a higher ratio of Level 2 chargers.

Next, you'll need to determine where to place these chargers for maximum benefit. Performing market research on the demand for chargers in your area can help clarify this process, as can consulting with a financial advisor with regard to installation costs.

Speaking of: The easiest way to install EV chargers is to turn to an EV solutions provider. They'll do the research, install, and operate the charging stations for you. As an EV infrastructure provider, they likely qualify for more rebates than your business. They're also experts in their field and can guide you through permitting, rebate application, and installation. Finally, they're there to help should something go wrong with the chargers.

To learn more about the incentives set to benefit businesses that install EV charging stations, read 7 EV charging incentives for businesses going green.

Supercharge your electric vehicle charging station business

Moving into electric vehicle charging is a chance to power both a better world and a healthier bottom line, and investing in the right tools early can make both easier. That's why we at ChargeLab designed our CSMS for deep functionality and wide-ranging flexibility. No matter your hardware, we're here to help. Reach out today to learn more.