What are the precautions for charging lithium-ion batteries?

In the use of lithium batteries, it should be noted that after the battery is placed for a period of time, it enters a dormant state. At this time, the capacity of the lithium battery manufacturer for emergency power supply is lower than the normal value, and the use time is also shortened. However, the lithium battery is easy to activate, as long as the battery is activated after 3 to 5 normal charge and discharge cycles, and the normal capacity is restored. Due to the characteristics of the lithium battery itself, it is determined that it has almost no memory effect. Therefore, the new lithium battery in the user's mobile phone does not require special methods and equipment during the activation process.

To charge a Li-Ion battery, use a dedicated Li-Ion battery charger. Lithium-ion battery charging adopts "constant current/constant voltage" mode, first constant current charging, and it is changed to constant voltage charging when the lithium battery supplier closes the voltage for emergency power supply. For example, a battery of 800 mA.h capacity has a termination charging voltage of 4.2V. The battery is charged at 800mA (charge rate 1C) constant current. At the beginning, the battery voltage rises with a large slope. When the battery voltage is close to 4.2V, it is changed to 4.2V constant voltage charge. The lithium battery current gradually decreases, and the voltage does not change much. When the charging current drops to 1/10C (about 80mA), it is considered that the price of the lithium battery for emergency power supply is close to full, and the charging can be terminated (some chargers start the timer after 10C, and end charging after a certain time). It is not possible to charge a lithium-ion battery with a charger filled with nickel-cadmium batteries (three-cell nickel-cadmium batteries) (although the rated voltage is 3.6V), it is easy to cause overcharging due to different charging methods.

2 Charging voltage: The charging voltage at full charge is related to the negative electrode material of the battery. The coke is 4.1V, and the graphite is 4.2V. It is generally called 4.1V lithium ion battery and 4.2V lithium ion battery. When charging, be aware that the 4.1V battery cannot be charged with the 4.2V charger, otherwise there is a danger of overcharging (4.1V is different from the charger IC used by the 4.2V charger). Lithium-ion batteries have high requirements for charging, and they require sophisticated charging circuits to ensure safe charging. The termination charge voltage accuracy tolerance is ±1% of the rated value (for example, a 4.2V lithium-ion battery with a tolerance of ±0.042V), and over-voltage charging can cause permanent damage to the lithium-ion battery.

3 Charging current: The charging current of the lithium ion battery should be based on the recommendations of the battery manufacturer and require a limited current circuit to avoid over current (overheating). The commonly used charging rate is 0.25~1C, and the recommended charging current is 0.5C (C is the capacity of the battery, such as the battery with the nominal capacity of 1500mA.h, the charging current is 0.5*1500=750mA). It is often necessary to detect the battery temperature during high current charging to prevent damage to the battery or explosion due to overheating.

4 Charging temperature: When charging the battery, its ambient temperature should not exceed the temperature range listed in the product characteristics table. The battery should be charged within the temperature range of 0 to 45 ° C, away from high temperature (higher than 60 ° C) and low temperature (-20 ° C).

If the lithium ion battery is overcharged, over discharged or over current during charging or discharging, it may cause damage to the battery or reduce the service life. To this end, various protection components and protection circuits consisting of protection ICs have been developed, which are installed in the battery or battery pack to provide complete protection of the battery. However, overcharge and overdischarge should be prevented as much as possible during use. For example, the mobile phone battery should be separated from the charger in time when it is charging. When the depth of discharge is shallow, the cycle life will be significantly improved. Therefore, when using, do not wait until the battery is low on the phone to charge, and do not continue to use this signal, although some residual capacity is available when this signal appears.

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