18650 lithium battery cells charge and discharge protection circuit, 18650 lithium battery cells protection board principle. The design of 18650 lithium battery cells charging circuit and discharge protection circuit is very important. Overcharging, over-discharging and short-circuiting of lithium-ion batteries are strictly prohibited during use, otherwise it will cause the battery life to be shortened or catch fire. Usually we need to pay attention to the charging voltage and charging current of lithium batteries, and then select the appropriate charging chip.

　　18650 lithium battery cells charge and discharge protection circuit

　　Lithium-ion battery protection circuits include overcharge protection, overcurrent/short circuit protection and overdischarge protection, which require high accuracy of overcharge protection, low power consumption of the protection IC, high withstand voltage, and zero-volt rechargeability.

　　The protection function of lithium batteries is usually completed by the protection circuit board and PTC. The protection board is composed of electronic components. It accurately monitors the voltage of the battery core and the current of the charge and discharge circuit at all times in an environment of -40°C to +85°C, and controls it in a timely manner. On and off of the current loop; the main function of PTC is to protect the battery in high temperature environments and prevent battery combustion, explosion and other vicious accidents.

　　Lithium batteries are rechargeable batteries. Generally, lithium batteries are fully charged at 4.2V. There are also batteries with other voltages.

　　1.Charging of 18650 lithium battery cells

　　The maximum charge termination voltage of a single 18650 lithium battery cells is 4.2V. It cannot be overcharged, otherwise the battery will be scrapped due to too much loss of lithium ions in the positive electrode. When charging lithium batteries, a dedicated constant current and constant voltage charger should be used. First charge with constant current until the voltage at both ends of the 18650 lithium battery cells is 4.2V, then switch to constant voltage charging mode; when the constant voltage charging current drops to 100mA, Charging should be stopped.

　　The charging current (mA) can be 0.1~1.5 times the battery capacity. For example: for a 1350mAh 18650 lithium battery cells, the charging current can be controlled between 135mA~2025mA. The conventional charging current can be selected to be around 0.5 times the battery capacity, and the charging time is about 2 to 3 hours.

　　2. Discharge of 18650 lithium battery cells

　　Due to the internal structure of the 18650 lithium battery cells, all lithium ions cannot move to the positive electrode during discharge. A part of the lithium ions must be retained at the negative electrode to ensure that the lithium ions can be inserted into the channel smoothly during the next charge. Otherwise, battery life will be shortened. In order to ensure that some lithium ions remain in the graphite layer after discharge, the minimum discharge termination voltage must be strictly limited, which means that the 18650 lithium battery cells cannot be over-discharged.

　　The discharge termination voltage of a single-cell 18650 lithium battery cells is usually 3.0V, and the minimum cannot be lower than 2.5V. The length of battery discharge time is related to battery capacity and discharge current.

　　Things to note when designing 18650 lithium battery cells circuits

　　●Overcharge and overdischarge of lithium batteries will affect the life of the battery.

　　●Pay attention to the charging voltage and charging current of the 18650 lithium battery cells. Then choose the appropriate charging chip.

　　●Be careful to prevent overcharging, over-discharging, short-circuit protection and other problems of lithium batteries.

　　●After design, a lot of testing is required.

　　18650 lithium battery cells protection board principle

　　The reason why lithium batteries need protection is determined by its own characteristics. Since the material of the 18650 lithium battery cells itself determines that it cannot be overcharged, overdischarged, overcurrent, short-circuited, or charged and discharged at ultra-high temperatures, lithium batteries always appear with a delicate protective board and a current fuse.

　　The protection function of lithium batteries is usually completed by a protection circuit board and current devices such as PTC. The protection board is composed of electronic circuits and can accurately monitor the voltage and charge return circuit of the battery core at all times in an environment of -40°C to +85°C. Current, timely control the on and off of the current loop; PTC prevents severe damage to the battery in high temperature environments.

　　The function of the 18650 lithium battery cells protection board is to protect the battery from discharge, overcharge, and current, as well as output short-circuit protection. The 18650 lithium battery cells protection board has overcharge protection, discharge protection, overcurrent protection, and short circuit protection. The protection board of the integrated solution also has disconnection protection. In addition, balancing, temperature control, and soft switching functions can be optional.

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