How to charge lithium-ion batteries to facilitate people's use?

The design idea of u200bu200bsolar chargers for lithium-ion batteries using solar charging The charging of lithium-ion batteries has always been a problem for users of lithium-ion batteries. How to charge to facilitate people's use is also a headache for lithium-ion battery manufacturers. Don't worry about this issue today, because we have found an environmentally friendly and convenient way to charge the battery: solar energy. Today, lithium-ion battery manufacturers share the design concept of lithium-ion battery solar chargers: Maximum Power Point Tracking Maximum Power Point (MPP) is the working area where solar cells can obtain the maximum power [1]. The graph in Figure 1 shows this area. This figure shows the typical output current and the relationship between output power and voltage curve of MPP dual solar panels. The MPP on the curve is obvious because it is the voltage and current output corresponding to the maximum power of the solar panel. MPP is related to ambient temperature and light, so it changes with time. It is recommended that when using a solar charger, there must be a corresponding circuit to track the continuous changes of the MPP with environmental conditions. The MPPT method includes simple open-loop technology (the panel voltage is maintained at a fixed open-circuit voltage) and complex microcontroller-like technology (measures the input and output power, and then correctly adjusts the panel voltage). Reverse leakage protection Reverse leakage refers to the phenomenon that the charge stored in the battery is lost and returned to the power source. When the battery voltage is higher than the power supply voltage, reverse leakage occurs. When this happens, the power source becomes a load on the battery and no longer charges. This state will not occur when using a wall adapter or a USB power supply, because the voltage output of both is always higher than that of a lithium-ion power supply. When using solar panels, in the case of insufficient light, the voltage of the solar panels is lower than the battery voltage. Figure 2a shows a schematic diagram of a USB power charger connected to a battery. When the switch S1 is closed, the power supply is disconnected from the battery, and the battery has no current. When using solar panels, if the same layout is used, when the solar panel voltage is lower than the battery voltage, the switch body diode is turned on. A common method to solve this problem is to use back-to-back switch charging termination. In the pre-stabilization stage, the battery is charged with a constant current of 0.1c (usually), and the battery voltage is slowly increased to about 2.5v. This stage is only used for deep discharge batteries. When the battery voltage rises above 2.5v, it is charged with a constant current. In the constant current charging stage, the battery is usually charged with 1C constant current until the battery voltage reaches ~4.2v. When the battery voltage reaches ~4.2v, charge at 4.2v constant voltage. At this stage, the current entering the battery needs to be monitored. When the battery current drops to 0.1°C, charging stops. In the constant voltage charging phase, the current into the battery decreases because the battery impedance increases when the battery is fully charged. When the current drops below 0.1°C, the charging power supply must be completely disconnected from the power supply. If it is not completely disconnected, metal lithium plating may occur, which will make the battery unstable and cause danger. We must stop charging the lithium-ion battery to maintain the maximum capacity of the battery. Solar panel crash protection In some traditional chargers, we know the current and voltage of the power supply in advance. Therefore, the charger circuit is specially designed to run the power supply within the specified range. When using solar panel output, the current and open circuit voltage are dynamic, which depends on the surrounding environment. Therefore, designing a control loop for a solar charger is more challenging than a wall adapter. The system uses solar energy to charge lithium-ion batteries in an attempt to maintain this process without accidentally crashing the panels. Because if the voltage of the solar panel drops sharply, you cannot get useful electricity from the solar panel. Solar panels are more likely to collapse during the constant current charging phase. At this stage, the battery board may not be able to supply the current needed to charge the battery. When this happens, the panel voltage begins to quickly collapse. Therefore, the charger must be able to detect the rapid drop in the solar panel voltage and immediately reduce the current drawn from the panel to prevent the panel from collapsing. Solar chargers can provide a mobile, environmentally friendly charging method for lithium-ion batteries. When designing a solar charger, there are many problems that cannot be encountered when designing a wall adapter charger. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Analyze the technical characteristics of lithium iron phosphate batteries