18650 3500mah battery

　　Charge and discharge process

　　Lithium battery charging control is divided into two stages. The first stage is constant current charging. When the battery voltage is lower than 4.2V, the charger will charge at a constant current. The second stage is the constant voltage charging stage. When the battery voltage reaches 4.2V, due to the characteristics of lithium batteries, if the voltage is higher, it will be damaged. The charger will fix the voltage at 4.2V, and the charging current will gradually decrease. When the current When it is reduced to a certain value (usually 1/10 of the set current), the charging circuit is cut off, and the charging completion indicator light is on, indicating that the charging is complete.

　　Excessive charging and discharging of lithium-ion batteries will cause permanent damage to the positive and negative electrodes. Excessive discharge causes the carbon sheet structure of the negative electrode to collapse, and the collapse will prevent lithium ions from being inserted during charging; overcharging causes too many lithium ions to be embedded in the carbon structure of the negative electrode, and some of the lithium ions can no longer be released.

　　Some chargers are implemented with cheap solutions, and the control accuracy is not good enough, which may easily cause abnormal charging of the battery and even damage the battery. When purchasing a charger, try to choose a big brand 18650 lithium-ion battery charger. The quality and after-sales are guaranteed to prolong the service life of the battery. The brand-guaranteed 18650 lithium-ion battery charger has four protections: short-circuit protection, over-current protection, over-voltage protection, battery reverse polarity protection, etc. Overcharge protection: When the charger overcharges the lithium-ion battery, in order to prevent the internal pressure from rising due to temperature rise, the charging state needs to be terminated. For this reason, the protection device needs to monitor the battery voltage, and when it reaches the battery overcharge voltage, it activates the overcharge protection function and stops charging. Over-discharge protection: In order to prevent the over-discharge state of the lithium-ion battery, when the voltage of the lithium-ion battery is lower than its over-discharge voltage detection point, the over-discharge protection is activated, the discharge is suspended, and the battery is kept in a low quiescent current standby mode. Over-current and short-circuit protection: When the discharge current of the lithium-ion battery is too large or a short-circuit occurs, the protection device will activate the over-current protection function.