A charger that is fixedly installed on an electric vehicle
Oct 30,2022 | TCcharger
The on-board charger refers to the charger that is fixedly installed on the electric vehicle. It has the ability to fully charge the power battery of the electric vehicle safely and automatically. The charger can dynamically adjust the charging current or voltage according to the data provided by the battery management system (BMS). parameters, execute the corresponding action, and complete the charging process.
(1) It has the function of high-speed CAN network and BMS communication, and judges whether the battery connection state is correct; obtains battery system parameters, and real-time data of the whole group and single battery before and during charging.
(2) It can communicate with the vehicle monitoring system through the high-speed CAN network, upload the working status, working parameters and fault alarm information of the charger, and accept the start or stop charging control command.
(3) Complete safety protection measures:
· AC input overvoltage protection function.
· AC input undervoltage alarm function.
· AC input overcurrent protection function.
· DC output overcurrent protection function.
· DC output short circuit protection function.
· Output soft start function to prevent current impact.
· During the charging process, the charging function can ensure that the temperature, charging voltage and current of the power battery do not exceed the allowable values; it also has the function of limiting the voltage of the single battery, and automatically adjusts the charging current dynamically according to the battery information of the BMS.
· Automatically judge whether the charging connector and charging cable are connected correctly. When the charger is correctly connected with the charging pile and the battery, the charger can start the charging process; when the charger detects that the connection with the charging pile or the battery is abnormal, it will stop charging immediately.
· The charging interlock function ensures that the vehicle cannot be started until the charger is disconnected from the power battery.
· High-voltage interlock function, when there is a high voltage that endangers personal safety, the module locks without output.
· With flame retardant function.
Car charger charging system:
There are many classification methods for new energy vehicle charging systems. According to whether the charging system is in direct contact with the public power grid, it is divided into contact charging system and inductive charging system. The contact charging system has the characteristics of simple structure, low cost and high power transmission efficiency, and is currently the mainstream charging system. The inductive charging system requires a small power socket or a charging cable, and the electric energy is wirelessly transmitted to the power battery in the car through the charging board buried in the road to realize charging. The inductive charging system has strong versatility, simple operation, labor cost saving, saving However, the structure is complex, the efficiency is low, and the cost is high, and it is currently used in a small range of public charging fields such as buses .
According to whether the charging system is installed in the car, the charger is divided into an on-board charging system and an off-board charging system. The on-board charging system is installed inside the vehicle and has the advantages of small size, good cooling and sealing, and light weight. It has the advantages of wide range of use and high power, but it is large in size, heavy in weight and difficult to move. It is mainly suitable for fast charging of new energy vehicles.
According to the charging time, the charger is divided into a slow charging system and a fast charging system, which correspond to two charging modes: AC power supply and DC power supply . The charging system is mainly composed of cables from the outside of the vehicle to the power supply end, charging interfaces and cables, on-board charging, high-voltage wiring harnesses, high-voltage power distribution equipment, power batteries and their controllers. The charging pile or household AC power supply is connected to the vehicle charger through the vehicle interface and wiring harness, and the AC 220V power supply is converted into DC power to charge the power battery. The charging process is carried out by the CAN communication interaction between the on-board charger and the BMS to ensure the safety of the charging process. Compared with the slow charging system, the structure of the fast charging system is relatively simple, and the vehicle-end components involved are only the charging interface, the fast charging wiring harness, the power battery and its controller. The power supply equipment of the fast charging system is a charging pile, and the charging pile includes a power supply module, a billing system, a communication and control system, a card reading and authorization system, etc. The fast charging system directly converts the three-phase 380V industrial power into DC power to charge the power battery. During the charging process, the communication module of the charging system communicates with the BMS to ensure safety.
②Charger charging method
Different charging methods of batteries will have different effects on battery life. Adopting appropriate charging methods is of great significance to prolong the service life of batteries.
Common on-board charger charging methods include constant voltage charging, DC charging, staged charging, and pulse charging. In constant voltage charging, the charging voltage remains unchanged during the entire charging process, and the charging current gradually decreases with the increase of charging time. When the charging current is less than a certain value, the specific charging is stopped. The energy consumption during the whole charging process is small, which can effectively avoid overcharging of the battery, and the control is simple and easy to operate. However, the initial voltage value of the battery to be recharged is often small, resulting in a large charging current at the initial stage of charging. On the one hand, excessive current will cause the occurrence of battery polarization and affect the charging speed; on the other hand, it will cause the battery temperature to rise rapidly, seriously It is easy to burn out the battery and cause an accident. Therefore, at the beginning of charging, the charging current value needs to be limited to keep the battery charged within an acceptable current range.
At the beginning of DC charging, a constant current is used to charge the power battery. When it is about to be fully charged, a constant small current is used for floating charging, which is used to supplement the remaining power and compensate for battery self-discharge. When the charging voltage reaches the rated voltage, the charging is stopped. Constant current charging avoids the problem of excessive constant voltage charging current, and the current is always limited within the acceptable range of the battery pack.
Staged charging can be divided into two-stage or three-stage charging according to the actual application. The first stage is constant current charging, which uses a large current to quickly charge the battery so that the voltage of the battery reaches a certain voltage value (set according to the voltage of the power battery pack; the second stage is constant voltage charging, and continues with a smaller current than the constant current. Charge the battery to reduce the gas production of the battery; the third stage is float charging, charging the battery with trickle to ensure that the battery can be fully charged, and when the control system detects that the charging current is less than a certain set value, the charging is terminated. The combination of staged charging The advantages of constant voltage and constant current charging methods are beneficial to reduce the polarization of the battery and avoid the impact of overcharge and high current charging. At present, most of the charging adopts stage charging.
The charging voltage and current of constant voltage charging, constant current charging and phased charging are continuous, and there is not enough rest time for the battery to eliminate polarization. Polarization can cause the battery to overheat, gassing, etc., limiting the charging speed. Seriously affect battery life. The pulse charging method and the positive and negative pulse charging method use discontinuous charging current, which can effectively reduce or eliminate the occurrence of polarization, speed up the charging speed and prolong the service life of the battery.
The pulse charging method adopts the pulse charging interval to provide the battery with sufficient rest time, which is conducive to the full reaction of the active substances inside the battery, effectively reducing and eliminating the occurrence of polarization, and can be charged with a larger current without worrying about it. Overheating of the battery can effectively improve the charging efficiency, shorten the charging time and prolong the battery life.
The positive and negative pulse charging method is an improvement on the pulse charging method. The whole charging process includes positive pulse charging, intermission rest and negative pulse discharge. Positive pulse charging is performed first, and after a period of rest, a short negative pulse discharge is performed. The short-term negative pulse discharge of the battery can effectively remove the occurrence of polarization, speed up the electrochemical reaction inside the battery, and reduce the battery temperature. Although part of the electric energy is lost, the battery can be charged with a higher charging current, which can effectively speed up the charging. Speed and improve charging efficiency, prolong battery life.