Design and implementation of a portable solar charging device for electric vehicles

　　1 Introduction

　　Since electric vehicles are light, convenient, green and environmentally friendly, many people choose them as a means of transportation. However, some shortcomings of electric vehicles have also brought inconvenience to the majority of users, such as the short life of electric vehicle batteries, limited power, and short mileage; it is inconvenient to charge in some high-rise residents of some communities; and its shortcomings are more prominent in places where there is no city electricity in the wild. In the context of increasingly severe environmental pollution and energy situations, solar energy, as a clean energy source, is inexhaustible. At present, its application technology is very mature and the cost is constantly decreasing. In this context, linking solar power generation with the huge market of electric vehicles must have a very broad application prospect, but there are very few such related products in China at present. Here, a solar charging device is designed to charge electric vehicles in a timely and convenient manner in response to some shortcomings in the use of electric vehicles.

　　2 Implementation plan

　　The charging control module of the solar charging device here is a high-power Boost converter based on the UC2843 current-mode PWM control chip. The charging implementation scheme is shown in Figure 1. The output of the solar panel is directly used to charge the battery pack of the electric vehicle after DC/DC Boost conversion, and at the same time assists in powering the motor load. The solar panel and the charging control module are fixed on the back seat of the electric vehicle, and the electric vehicle can be charged uninterruptedly when driving and docking. Most of the commercialized electric vehicles currently use sealed lead-acid batteries. For 48 V and 36 V electric vehicles, the fixed output voltage is 56 V or 42 V, and constant voltage charging is used.

　　　　5 Prototype circuit design

　　Figure 4 is the schematic diagram of the Boost circuit controlled by UC2843. Ui is used as the input of the boost conversion and also supplies power to UC2843. R2 and C6 are RC oscillators, which control the operating frequency and maximum output duty cycle of the main circuit; R1, C1, and R6 are output voltage feedback regulators, which proportionally feed back the output voltage feedback signal, that is, the output voltage Uo, to the COMP terminal. Uo can be continuously adjusted by adjusting R6.

　　6 Performance indicators and economic and technical indicators

　　The solar panel in the charger prototype here uses a 30 W polycrystalline silicon single board. For 36 V electric vehicles, the open-circuit output voltage of the charging device is adjusted to 42 V. According to actual measurements, under various sunshine conditions, the output voltage fluctuation does not exceed 1%. Under strong sunlight, the charging current peak is about 400 mA, and on rainy days, the charging current is also about 30 mA. The performance indicators of the device are as follows: Ui is 10-32 V; Uo is an adjustable potentiometer, outputting a continuously adjustable voltage of 35-60 V; the maximum output current is 5 A; the maximum input current is 16 A; the maximum output power is 120 W; the DC/DC module conversion efficiency is 80%.

　　Electric vehicles are very common nowadays. The design life of general batteries is 8 years, but the service life of electric vehicle batteries is only 2 to 3 years. The main reason is unreasonable charging. If the battery is undercharged or over-discharged for a long time, the lead sulfate inside will crystallize and the plate will sulfide, causing the battery to "starve to death". Using a solar charging device, as long as it is daytime, you can charge your electric vehicle anytime and anywhere, prevent battery plate sulfation, and greatly extend the battery life.

　　In addition, in some high-rise residential areas and in rural areas, using solar energy to charge electric vehicles will bring great convenience and can continuously increase the mileage. In some special cases, emergency charging is also possible. The economic and technical indicators of the solar charging device for electric vehicles are as follows: ① Easy installation, fixed on the rear iron frame of the electric vehicle with screws; ② It can be used to charge 36 V and 48 V electric vehicles; ③ It can charge the battery during the driving of the electric vehicle, and can also output power to the motor to drive the motor together, increasing the mileage: ④ Because it can continuously charge the battery, it can prevent and remove the sulfation of the battery plate, restore the battery capacity, and effectively extend the battery life.

　　7 Conclusion

　　Solar charging of electric vehicles is a project with broad application prospects and great market potential. In the charging device designed here, the boost control circuit based on UC2843 is simple and reliable, low cost, the entire charging device is simple and practical, and the experimental effect is good. In the future, more functions such as solar maximum power point tracking and charging monitoring will be further added, and the appearance of the solar panel will be improved to enhance the overall aesthetics after installation, making the device more perfect.