DC EV charger technical evolution analysis

1. The evolution trend of DC EV charger scenarios.

1.1 Coordinated development from a single centralized charging station to a diversified scenario supplemented by centralized + distributed

EV charger station

In the past, DC EV charger stations took the form of centralized charging stations occupying key locations in cities and traffic as the vast majority of their existence. This method of station construction has high requirements for site selection and power capacity. Due to the current status of lithium battery technology, the short-term DC EV fast charging (full) time cannot reach the same experience as a fuel car. For conventional passenger car charging, it usually takes 1.5 to 2 hours to charge from 10% to 100%.  Therefore, due to the charging time, most of the charging needs of centralized charging stations are mainly for operating vehicles (due to the continuity of business operations, continuous high-power supplementary power is required), and a small proportion of private car owners.

According to the operating data of mainstream charging operation platforms and data detection platforms, the utilization rate of DC EV charging piles in centralized DC fast-charging stations is still low, generally below 15%. Although the proportion of new energy vehicles is a realistic factor, it is undeniable that the location of most charging stations and the analysis of target users’ positioning is not sufficient, which actually causes a certain amount of waste of resources.

The destination distributed charging station will be an effective supplement to improve the charging network. If the traditional centralized charging station is “people looking for piles”, then the destination distributed charging station will be “pile waiting for people.” Charging users are charging while staying at the destination (usually more than 1 hour), there aren’t high requirements on charging speed (a certain degree of recharge is sufficient), that is, the charging power of the charging pile is mainly 20 to 30 kW (multiply Mainly use cars). At the same time, the purpose is that the location and power capacity requirements of the distributed charging station are less difficult, and the difficulty of setting up the station is relatively low, and it has general promotion conditions.

 

1.2 Centralized charging stations are subdivided into “ordinary environment centralized charging stations” + “rigorous environment high-protection centralized charging stations” + “centralized overcharging stations above 350kW (liquid cooling)” according to application scenarios (environment)

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As we all know, EV chargers generally reflect frequent faults due to environmental reasons in actual field applications. The reason is mainly that the IP  protection class of the charging module, the core component of the EV charger, is IP20, which is weak in protection against harsh environments (sand dust, salt spray, condensation, conductive particles), and the power density of the charging module is relatively large. It is generally working under high voltage and high current conditions, which further causes the sensitivity to harsh environments. Therefore, it is necessary to separate the harsh environment charging station from the conventional environment charging station and adopt a special charging station (charging pile) design form. At present, there are two feasible upgrade solutions for charging stations in harsh environments,

a) using an IP65 independent air duct charging module;

b) using an IP20 charging module + heat exchanger/air conditioning cooling solution.

With the continuous improvement of the demand for the charging experience (speed) of electric vehicles in the whole society, the battery side, the electric vehicle manufacturer, and the supporting charging pile system solutions are all undergoing continuous changes. The high-voltage battery platform (above 800V) guided by the electric vehicle manufacturer adopts new battery technology to support 4C~6C charging. It requires a “supercharging pile” (hereinafter referred to as “supercharger” (hereinafter referred to as “supercharger”) with a charging current of more than 350kW and a single gun charging current supporting a maximum of 500A. Fill the pile”). The charging module in the supercharged pile From the opinions of industry participants, it is generally believed that the use of a “liquid cooling module” is an ideal technical solution

2. Development trend of DC EV charger technology

After more than ten years of development and full competition in the DC EV charger industry, the current market application status has revealed several major problems:

1. The technical solution is relatively simple, and more than 90% of the direct ventilation cooling solutions are adopted. From the perspective of application effects, it cannot meet the diversification requirements. Application scenarios require environmental adaptability and high reliability.

2. Market competition is highly concentrated on price competition, rather than competition on “product value innovation”. As a result, manufacturers generally reduce costs and reduce product reliability.

3. Due to a simple technical solution, the environmental protection capabilities of the EV chargers are insufficient, resulting in large maintenance workloads and high maintenance costs, which ultimately lead to a high TCO throughout the life cycle.

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2.1 The trend of charging pile system capacity in centralized stations is increasing

With the general increase in the battery capacity of electric vehicles, there is also a general demand for an increase in the single gun capacity of EV chargers. Take the A-class electric vehicle e-golf as an example, the battery capacity is 35.8kWH, which can support a maximum charging power of 1C 35.8kW, that is, the maximum charging power demand of the A-class entry model in the state of power loss has exceeded 35kW.

From the actual application of the current market, the 120kW dual gun is currently a large proportion of the EV chargers specifications in the market, and there is a trend to continue to evolve to the 160kW dual gun capacity. The essential reason comes from the increase in the density of the power battery and the increase in the charging speed. The increase in the capacity of the EV charger system will also bring about the configuration requirements of the increase in the granularity of the charging module.

2.2 Trend of high-voltage EV chargers

An important factor affecting the speed of the popularization of electric vehicles is the improvement of the charging experience. The two factors that affect the highest proportion of the charging experience are the convenience of finding a charging station (EV charger), and another important factor is the charging speed. At present, it generally takes 1.5 to 2 hours for electric passenger cars to go from losing electricity (10% SOC) to full (100% SOC). There is still a lot of room for improvement in the charging time, and it will gradually catch up with the 15-minute full fuel time of fuel vehicles.

The high-voltage electrical platform of electric vehicles is a trend in the current technological evolution of electric vehicle manufacturers. In the case of the same charging current, the high-voltage battery pack can support greater charging power and shorter charging time. Foreign Porsche has launched 800V Taycan models in 2020, and domestic BAIC will launch Jihu in May 2021 to support 800V charging. At the same time, Xiaopeng, Weilai, Guangzhou Automobile, and other major electric vehicle manufacturers have released information on planning high-voltage models above 800V. It is expected in the next 2 years. The number of high-voltage models above 800V will gradually increase during the year.

Under the trend of the high-voltage evolution of electric vehicles, there is an urgent need for EV chargers to increase the upper limit of the charging voltage to 1000V to support the high-voltage vehicles that are commonly used in the future. According to theoretical analysis, for 90kWh equipped with lithium battery (about 700 kilometers), it is charged with 1080V/maximum 500A high-voltage platform, the maximum charging power is 540kW, reaching 6C charging capacity, and the battery can be fully charged in 10 minutes. According to market information, GAC, Xiaopeng, Weilai and other OEMs are already planning high-rate rechargeable battery packs and new models (supporting 4C to 6C).

Based on the development needs of the market, the State Grid Corporation of China has clearly required the EV charger specifications to support up to 1000V charging in the charging pile collection project in May 2021. This is undoubtedly an important market signal.

2.3 Design requirements for high reliability and high compactness of destination charging stations

For destination charging stations, there is already a relatively general market demand, and a new type of small DC charging pile is needed to meet the short-term stay time DC supplement. And in this scenario, it is generally faced:

1. The installation space is limited;

2. The appearance of the charger is required to be more beautiful (especially in a commercial space environment);

3. The models installed outdoors have higher requirements for environmental protection/reliability;

4. In most cases, there is no one on duty, which in turn puts forward a high demand for high reliability/maintenance-free products. The above-mentioned four major application requirements put forward two major design requirements of high reliability and high compactness for small DC chargers, which put forward higher requirements on the design of charger R&D and production enterprises.

3. The development trend of DC EV charger charging module technology

As the core key component of the EV charger system, the technical solution, performance, and reliability of the charging module directly affect the overall performance of the EV charger system. Judging from the development of the past ten years, in the early days, there were any ready-made technical solutions that could be borrowed on the market (IP20 direct ventilation technical solutions in the communication power supply industry), and they were directly inherited into the EV charger industry in the form of “usage doctrine”. However, when the market has experienced more than ten years of development, the unique application environment of EV chargers has proved that the traditional single technical solution cannot support the future development of the industry to a healthier and more advanced goal. At this time, it is necessary to make innovative thinking and design of new technical solutions from the technical solution of the charging module itself, so as to promote the development of the industry in a healthier and more advanced direction.

bluesky EV charger workshop

3.1 The market with a larger share of 20kW is developing towards a market with diversified configurations of 20/30/40kW

In the current domestic market, 20kW modules account for about 60% of the market capacity, and a large proportion of the remaining capacity is occupied by 30kW, and some 40kW modules. With the increase in battery capacity and charging rate of electric vehicles in recent years, there has been an obvious actual market development trend: the market with a larger share of 20kW is gradually developing towards diversified specifications of 20kW, 30kW, and 40kW.

The main reason is that EV chargers with different powers and different charging gun power distribution requirements require different charging modules with the most suitable power granularity. Therefore, in the standard specifications of the charging module, it is advisable to develop a series of charging modules with different capacities.

3.2 The design scheme of uniform size/uniform interface should be adopted for the 30kW/40kW charging module

With the development and evolution of charging module technology and the gradual maturity of the market application scale, the design direction of charging module products is also continuing to improve in the direction of high reliability and high power density. For the already clear demand for 30kW/40kW charging modules in the market, it is necessary to reduce the repetitive design of EV chargers due to the iteration of module specifications due to the failure to consider the compatibility of long-term development in the process of upgrading and evolving charging pile standards. Work. Therefore, the 30kW/40kW specification module should be designed with the same structural size and the same interface size from the beginning of the design.

3.3 The upper limit of the output voltage range is applied from 750V to 1000V for high voltage landing

The continuous advancement of the high-voltage electrical platform of the electric vehicle factory has promoted the upgrading of the supporting infrastructure of the EV chargers. The 1000V maximum output voltage has formed a consensus in the charging module industry, and major charging module manufacturers have gradually introduced the 1000V high-voltage charging module specifications.

UU Green Energy took the lead in launching 30kW/1000V charging modules in the first half of 2018, and successively launched 20kW/1000V and 40kW/1000V modules in 2019 and 2020, respectively. Huawei, Infineon, Yonglian, Tonghe, ZTE and other manufacturers have also launched 1000V charging module products in 2020 and 2021, respectively.

Due to the high power density of 30kW/40kW, higher voltage, and higher current, it poses greater challenges to product reliability. Some manufacturers that launched 30/40kW late still need a certain amount of market application for a certain period of time to verify product reliability.

3.4 Promotion and application of independent air duct design scheme/IP65 high protection scheme

In the early stage of market development, mature IP20 direct ventilation technology products have supported the charging industry through the development stage of nearly 10 years. In this process, the inherent outdoor, high temperature, sand, dust, moisture and other environmental factors inherent in the installation and use environment of the charging pile have brought a greater test to the reliability of the product. Because the technical route itself (direct ventilation) is difficult to meet the application requirements in harsh environments, the charging pile products have a high failure rate and high operation and maintenance costs. Coupled with the lower prices after the full competition (and the need to bear continuous maintenance costs), it has caused great pressure on the business development of most pile enterprises. There are also some manufacturers in the industry, claiming to adopt a “semi-independent air duct” improvement plan. After analyzing the details, it is actually used a glue filling process to cover and protect the devices on the board, and the higher devices above the board will still face the effects of long-term dust, moisture, and salt spray. Although it can delay the occurrence of failures to a certain extent, it does not essentially solve the environmental protection problem of internal devices.

Under this condition, individual manufacturers have introduced an “independent air duct technology solution” that adopts an innovative solution design. The independent air duct technology is different from the conventional IP20 direct ventilation technology. Through innovations in the structural design and the layout of key internal components, the inside of the module is divided into upper and lower layers. The upper encapsulation is for devices that are sensitive to the environment (sand dust, moisture, salt spray, etc.), such as capacitors, semiconductors, magnetic components, etc.; the lower layer is for components that are not affected by the environment, such as radiators, and the lower air duct is more unobstructed, To ensure the heat exchange efficiency.

Take a 120kW EV charger as an example, using IP65 high protection modules and conventional IP20 modules, using the entire life cycle of 10 years of service life, to statistically compare the overall TCO (Total Cost of Ownership). The data shows that since the third year, the economic advantage of the total cost of ownership of the IP65 high protection module has been reflected. Compared with IP20 piles, the 5-year TCO saves about 12,000 yuan, and the 10-year TCO saves about 52,000 yuan.

DC EV charger

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Wenzhou Bluesky Energy Technology Co., Ltd

www.evchargerchina.com
www.blueskynewenergy.com

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