First, we need to understand some basic concepts: 1. Both lithium batteries and solar modules generate direct current (DC); 2. Household electricity is 220V/50Hz alternating current (AC), which is very convenient to use; 3. The current size and direction of AC change with time, while the size and direction of DC do not change periodically; 4. Converting AC to DC is called rectification, and the equipment for this is called a rectifier. Converting DC to AC is called inversion, and the equipment for this is called an inverter.

Now let's talk about chargers. There are many types and shapes of chargers on the market, as shown in the figure below. The government has started to整顿 this chaos. In June 2022, the Ministry of Industry and Information Technology publicly solicited opinions on national standards such as "Safety Technical Requirements for Electric Bicycle Chargers", and the forms and specifications of electric bicycle chargers and plugs were officially exposed. This is the new national standard plug and charger for electric bicycles in the future, as shown in the figure below. Next, we will analyze chargers from three aspects: working principle, charging time, and common faults.

However, the basic principle remains the same. The simplified principle is shown in the figure below. The purpose of the rectification and filtering circuit is to convert the household AC voltage of 220V to a DC voltage of about 300V. Through the high-voltage switching circuit and voltage exchange, the low-voltage DC voltage required by the charger is generated. After charging control, the battery is charged. The function of the constant current and constant voltage charging control circuit is to maintain the stability of the current and voltage during charging to avoid damaging the battery. Chargers using this method have the advantages of small size, light weight, and high efficiency.

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