Lithium battery charging and discharging requirements and protection circuit

Lithium battery charging and discharging requirements; 1. Lithium battery charging: According to the structure and characteristics of the lithium battery, the maximum intermittent charging voltage is 4.2v, and it cannot be overcharged, otherwise the battery will be scrapped due to excessive lithium ions in the positive electrode. The charging and discharging requirements are relatively high, and a special constant current and constant voltage charger can be used for charging. In general, constant current charging is converted to constant voltage charging after charging to 4.2v/junction. When the constant voltage charging current drops to less than 100mA, intermittent charging is required. Charging current (mA)u003d0.1~1.5 times battery capacity (such as 1350mAh battery, its charging current can be controlled between 135~2025mA). The traditional charging current can be about 0.5 times the battery capacity, and the charging time is about 2 to 3 hours. 2. Discharge of lithium battery: Due to the internal structure of lithium battery, all lithium ions cannot move to the positive electrode discharge period, so it is necessary to keep lithium ions in a part of the negative electrode to ensure that lithium ions can be easily inserted into the channel in the future. Otherwise, the battery life will be shortened accordingly. In order to ensure that some lithium ions remain in the graphite layer after discharge, it is necessary to strictly limit the intermittent minimum voltage of discharge, that is, the lithium battery cannot be over-discharged. The discharge intermittent voltage is generally 3.0V/cell, and the minimum should not be less than 2.5V/cell. The battery discharge time is related to the battery capacity and discharge current. Battery discharge time (hours) u003d battery capacity/discharge current. Lithium battery discharge current (mA) should not exceed 3 times the battery capacity. (Such as 1000mAH battery, the discharge current should be strictly controlled within 3A) Otherwise, the battery will be damaged. Lithium battery packs on the market now have matching charge and discharge protection boards. Just control the external charge and discharge current. Lithium battery protection circuit: two lithium battery charge and discharge protection circuits. The overcharge control tube FET2 and the overdischarge control tube FET1 are connected in series in the circuit. The protection IC monitors and controls the battery voltage. When the battery voltage rises to 4.2v, the overcharge protection tube FET1 is cut off and the battery is charged intermittently. In order to prevent malfunctions, delay capacitors are usually added to external circuits. When the battery is in a discharging state and the battery voltage drops to 2.55v, the over-discharge control tube FET1 is cut off and the load is supplied intermittently. Over-current protection is to control FET1 to turn off when the load has a larger current flow cycle, and discharge it to the load intermittently. The purpose is to protect the battery and the field effect tube. The over-current detection uses the on-off resistance of the field effect tube as the detection resistance to monitor the voltage drop and perform intermittent discharge when the voltage drop exceeds the set value. There is also a delay circuit to distinguish between surge current and short-circuit current. The circuit has complete functions and reliable functions, but it is highly professional, and the dedicated integrated block is not easy to buy, and it is not easy for laymen to copy. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: Analysis of prospects for the recovery and reuse of lithium batteries