Lithium-ion battery charging precautions
In the use of lithium batteries, it should be noted that the battery will enter the dormant state after being placed for a period of time. 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. But lithium batteries are easy to activate, as long as 3-5 normal charge-discharge cycles can activate the battery and restore its normal capacity. Due to the characteristics of the lithium battery itself, it has almost no memory effect. Therefore, in the activation process of the new lithium battery in the user's mobile phone, no special method or equipment is required.
To charge the lithium-ion battery, a dedicated lithium-ion battery charger should be used. Lithium-ion battery charging adopts the "constant current/constant voltage" method, first constant current charging, and then changing to constant voltage charging when the emergency power supply lithium battery supplier nears the termination voltage. For example, a battery with a capacity of 800mA.h has a termination charging voltage of 4.2V. The battery is charged with a constant current of 800mA (charging rate of 1C). 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 charging. The current of the lithium battery 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 reaching 10C, and end the charging after a certain period of time). Do not use a NiCd battery charger (charged with three NiCd batteries) to charge Li-ion batteries (although the rated voltage is the same, both are 3.6V). Due to the different charging methods, it is easy to cause overcharge.
Charging voltage: The final charging voltage when fully charged is related to the negative electrode material of the battery. The coke is 4.1V, and the graphite is 4.2V, which are generally called 4.1V lithium-ion batteries and 4.2V lithium-ion batteries. When charging, it should be noted that the 4.1V battery cannot be charged with a 4.2V charger, otherwise there will be a danger of overcharging (the charger IC used by the 4.1V and 4.2V chargers is different). Lithium-ion batteries have high requirements for charging, and it requires sophisticated charging circuits to ensure the safety of charging. The tolerance of the termination charging voltage accuracy is ±1% of the rated value (for example, for a 4.2V lithium-ion battery, the tolerance is ±0.042V). Overvoltage charging will cause permanent damage to the lithium-ion battery.
Charging current: The charging current of the lithium-ion battery should be based on the recommendations of the battery manufacturer, and a current-limiting circuit is required to avoid overcurrent (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 a battery with a nominal capacity of 1500mA.h, the charging current is 0.5*1500=750mA). Battery temperature is often detected during high current charging to prevent battery damage or explosion due to overheating.
Charging temperature: When charging the battery, its ambient temperature cannot exceed the temperature range listed in the product characteristic table. The battery should be charged within the temperature range of 0 to 45°C, away from high temperature (above 60°C) and low temperature (-20°C) environments.
If the lithium-ion battery is overcharged, overdischarged or overcurrent during the charging or discharging process, it will cause damage to the battery or reduce its service life. For this reason, various protection components and protection circuits composed of protection ICs have been developed, which are installed in the battery or battery pack to obtain perfect protection for the battery. However, overcharge and overdischarge should be prevented as much as possible during use. For example, during the charging process, the mobile phone battery should be separated from the charger in time when it is nearly full. When the depth of discharge is shallow, the cycle life will be significantly improved. Therefore, when using, do not wait until the signal of low battery appears on the mobile phone before charging, and do not continue to use it when this signal occurs, although there is still some residual capacity available for use when this signal occurs.