Lithium-ion battery charging process
The charging process of a lithium-ion battery consists of two stages: a constant current charging stage and a constant voltage current decreasing charging stage. Overcharging and over-discharging of a lithium-ion battery can cause permanent damage to the positive and negative electrodes. Over-discharging causes the carbon layer structure of the negative electrode to collapse, which prevents lithium ions from inserting during charging; overcharging causes too many lithium ions to embed into the carbon structure of the negative electrode, resulting in some of these lithium ions never being released.
The optimal charge-discharge method for lithium-ion batteries to maintain performance is shallow charge and shallow discharge. Generally, the cycle life at 60% DOD is 2 to 4 times that at 100% DOD.
Phase 1: Trickle Charging. Trickle charging is used to pre-charge (recovery charging) fully discharged battery cells. When the battery voltage is below approximately 3V, a constant current of up to 0.1C is used to charge the battery.
Phase 2: Constant Current Charging. When the battery voltage rises above the trickle charging threshold, the charging current is increased to perform constant current charging. The constant current charging current is between 0.2C and 1.0C.
Phase 3: Constant Voltage Charging. When the battery voltage rises to 4.2V, constant current charging ends, and constant voltage charging begins. To achieve optimal performance, the voltage regulation tolerance should be better than +1%.
Phase 4: Charging Termination Unlike nickel batteries, continuous trickle charging of lithium-ion batteries is not recommended. Continuous trickle charging can cause plate plating in the lithium metal. This can destabilize the battery and potentially lead to sudden, rapid disintegration.
How do you charge a lithium-ion battery?
● Many mobile phone batteries and flashlight batteries indicate in their manuals that they need to be charged for 12 hours on the first charge to activate them, but this is actually unnecessary. Just charge them to full capacity normally, because lithium-ion batteries do not have a memory effect.
● It is recommended to charge overnight, as lithium-ion batteries are relatively delicate and the current fluctuation is smaller at night, making it suitable for charging.
● Do not intentionally discharge lithium-ion batteries before charging, as improper discharge can damage the battery. When charging, try to use slow charging and reduce fast charging; the charging time should not exceed 24 hours.
