The battleground in the era of electric vehicle charging!


1. The key technology to solve the pain point - super charging

1.1 Car Charging: The Source of Energy

The new energy vehicle market performed strongly. At present, the growth rate of new energy vehicles has accelerated significantly.

The acceleration of electrification: It has created a huge demand for charging. The global electrification trend is obvious, which is bound to generate a huge demand for charging.

On-board charging: the source of energy for new energy vehicles. Different from fuel vehicles, electric vehicles mainly rely on the on-board power battery to provide energy. Electric vehicles consume electricity continuously during driving. When the electricity is exhausted, the battery energy needs to be replenished. Its energy supplement form is to convert the energy of the grid or other energy storage devices into the energy of the battery, and this process is called charging. At the same time, OBC (on-board charger) has become a key component in the charging process, which is mainly responsible for charging the battery through the connection of the voltage of the grid through the charging pile or AC interface.

Charging classification: AC slow charging: that is, the traditional battery charging method, also known as conventional charging. AC charging equipment does not have a power converter, and directly outputs AC power and connects it to the car. The on-board charger converts AC power into DC power for charging. Therefore, the AC slow charging solution can be charged by connecting to a household power supply or a dedicated charging pile through the portable charger that comes with the vehicle.

The power of AC charging depends on the power of the on-board charger. At present, the on-board chargers of mainstream models are divided into 2Kw, 3.3Kw, 6.6Kw and other models. The current of AC charging is generally around 16-32A, and the current can be DC or two-phase AC and three-phase AC. At present, it takes 4-8 hours for the AC slow charging of hybrid vehicles to be fully charged, and the charging rate of the AC charging is basically below 0.5C.

The advantage of AC slow charging is that its charging cost is low, and charging can be completed without relying on charging piles or shared charging networks. However, the shortcomings of conventional charging are also very obvious. The biggest problem is that the charging time is long. At present, the cruising range of most trams exceeds 400KM, and the charging time corresponding to conventional charging is about 8 hours. For car owners who need long-distance driving , Charging anxiety on the road is far greater than other factors. Secondly, the charging mode of conventional charging is low-current charging, and its charging mode is linear charging, which cannot make good use of the characteristics of lithium batteries.

DC fast charging: The problem of charging electric vehicles with slow AC charging has always been a major pain point. With the increasing demand for higher efficiency charging solutions for new energy vehicles, fast charging solutions have emerged as the times require. Fast charging is fast charging, or ground charging. The DC charging pile has a built-in power conversion module, which can convert the AC power of the grid or energy storage equipment into DC power and directly input it into the battery in the car without going through the on-board charger for conversion. The power of DC charging depends on the battery management system and the output power of the charging pile, and the smaller value of the two is taken as the input power.

The representative of the fast charging mode is the Tesla super charging station. The current and voltage of the fast charging mode are generally 150-400A and 200-750V, and the charging power is greater than 50kW. This method is mostly a DC power supply method. The power of the charger on the ground is large, and the output current and voltage range are wide. At present, the fast charging power of Tesla on the market reaches 120Kw, which can charge 80% of the electricity in half an hour, and the charging rate is close to 2C. BAIC EV200 can reach 37Kw, and the charging rate is about 1.3C.

Control system: The conversion process of BMS charging equipment also needs to cooperate with the management system BMS (Battery Management System) of the power battery on the electric vehicle. The biggest advantage of BMS is that during the charging process, it will change the charging scheme of the battery according to the real-time state of the battery , its non-linear charging mode realizes fast charging under the two prerequisites of safety and battery life.

The functions of BMS mainly include the following categories:

Power state monitoring: The most basic power state monitoring content is the state of charge (SOC) monitoring of the power battery. SOC refers to the percentage of the remaining battery power and battery capacity, and is the main parameter for car owners to evaluate the cruising range of electric vehicles. The BMS monitors the battery parameter information (voltage, current, temperature, etc.) in real time by calling the data of multiple high-precision sensors on the battery pack, and its monitoring accuracy can reach 1mV. Accurate information monitoring plus excellent algorithm processing ensures the accuracy of battery remaining power assessment. During daily driving, car owners can set the target value of SOC to achieve dynamic optimization of vehicle energy consumption.

Battery temperature monitoring: Lithium batteries are highly sensitive to temperature. Whether the temperature is too high or too low, it will directly affect the performance of the battery cell, and in extreme cases, it will cause irreversible damage to the performance of the battery. BMS can be monitored by sensors to ensure a safe environment for battery operation. In winter when the temperature is low, the BMS will call the heating system to heat the battery cells to reach a suitable charging temperature to avoid the reduction of battery charging efficiency; while in the summer when the temperature is high or the battery temperature is too high, the BMS will immediately pass the cooling The system lowers the battery temperature to ensure driving safety.

Battery energy management: Manufacturing process errors or inconsistencies in real-time temperature of batteries will cause their voltages to vary. Therefore, during the charging process, some cells in the battery may have been fully charged, while the other part of the cells may not be fully charged. The BMS system monitors the voltage difference of the battery cells in real time, adjusts and reduces the voltage difference between each single battery cell, ensures the balance of charging of each battery cell, improves charging efficiency, and reduces energy consumption.

1.2 4C is expected to become an industry trend

The charging problem has become a pain point for consumers. The charging speed has always been used throughout the use of electric vehicles. The current rapid penetration and expansion of electric vehicles in the world has further amplified the impact of charging speed on the driving efficiency of car owners and user experience. Psychological anchoring: The energy replenishment of traditional fuel vehicles is very fast. In general scenarios, it takes no more than 10 minutes for fuel vehicles to refuel from entering the gas station to driving out of the gas station. Every highway stop. Taking a 400KMH traditional electric vehicle as an example, the charging speed of electric vehicles is generally upwards of 30 minutes, and the tight number of charging piles prolongs the pre-charging waiting time. The current charging technology has no advantage over the refueling method of fuel vehicles. The 10-minute psychological anchoring time of fuel vehicles is always the first standard for customers to measure the charging speed of electric vehicles.

The Supercharging standard was conceived. Definition of C: Usually, we use C to express the charge and discharge rate of the battery. For discharge, 4C discharge represents the current strength at which the battery is fully discharged in 4 hours. For charging, 4C means that at a given current intensity, it takes 1 hour to fully charge the battery to 400% of its capacity, that is, at a given current intensity, the battery can be fully charged in 15 minutes. What is 4C: 4C is not a new indicator, but an extension of traditional charging and discharging indicators such as 1C and 2C. The marginal effect of the boost is weaker. When the charging rate of the battery exceeds 4C, the technical difficulty increases and the current pressure on the battery is greater, but the positive effect brought about by the technical improvement becomes smaller. Therefore, we believe that 4C is currently the optimal solution that combines performance improvement and battery technology affordability.

The iterative process of power battery charging rate: In the early days, limited by the technological level at that time, neither the charging technology nor the battery technology allowed the battery to be charged at a higher rate. The rate is only 0.1C, and the increase of the charging rate will have a great impact on the battery life. With the continuous breakthrough of lithium battery technology and the continuous improvement of BMS, the charge and discharge rate of the battery has been significantly improved. The charging rate of the earliest AC slow charging scheme is below 0.5C. With the accelerated penetration of electric vehicles around the world in recent years, the charging technology of power batteries has made great breakthroughs, and the electric vehicles from 1C have rapidly evolved to 2C. In 2022, domestic cars equipped with 3C batteries will enter the market. On June 23, 2022, CATL released a new Kirin battery and said that 4C charging is expected to arrive next year.

Super charging will become the only way to upgrade charging technology. Like new energy vehicles, mobile phones also have a strong demand for charging speed, and charging technology is also constantly improving in the process of mobile phone development: from 1983, Motorola DynaTAC8000X achieved charging for 10 hours and talking for 20 minutes, and in 2014, OPPO Find 7 promoted charging Talking for 5 minutes for 2 hours, now many models can fully charge the 4500mAh battery in 15 minutes. The charging protocol of smartphones has also been upgraded from 5V 1.5A of USC BC 1.2 in 2010 to USB PD 3.1 in 2021, and the maximum voltage can support 48V. We believe that whether it is a smartphone or a new energy vehicle, the realization of fast charging will greatly improve the product experience, and it is also the only way to upgrade technology. In the future, 4C charging for electric vehicles will also become an industry trend.

1.3 Multi-enterprise deployment of super charging

At present, many companies have released their own fast charging layout plans, and related models have been released since 2021: Porsche launched the first 800V fast charging platform electric car; BYD e platform 3.0 was released, corresponding to the concept model ocean-X; Geely Jikrypton 001 is equipped with an 800V fast charging platform. At the same time, Huawei released its AI flash charging full-stack high-voltage platform, which is expected to achieve 5-minute fast charging by 2025.

1.3.1 Huawei: AI flash charging full-stack high-voltage platform will realize 5-minute fast charging

"High current" and "high voltage" paths coexist, and the latter is more cost-effective. In order to achieve higher charging power to achieve the purpose of fast charging, it is necessary to increase the current or voltage. At present, there are more companies on the market that adopt more "high voltage" technology paths than "high current". Huawei said: When using the "high voltage" technology path, the cost of the vehicle's BMS and battery modules is the same as the "high current" path, but because it does not need to consider the impact of high current, the cost of its high-voltage wiring harness and thermal management system is relatively low . 800V may become the mainstream. Today's mainstream models still use a 200V~400V voltage architecture. In order to achieve higher power to meet fast charging requirements, the current may double, which will affect the heat dissipation and performance of the vehicle. Nowadays, components including power devices such as SiC, high-voltage connectors, and high-voltage charging guns have matured. It is a better choice to choose a higher voltage while ensuring that the current is in a relatively safe range.