When the lithium battery discharges an external load, its voltage gradually decreases with the discharge process. When the battery voltage drops to 60% of full voltage, its available capacity (40%) is completely discharged. If the battery continues to discharge, it will be permanently damaged. For this reason, lithium batteries are equipped with an over-discharge protection circuit, that is, when the available capacity is exhausted, the operating voltage is no longer supplied to the external circuit.
For example: the lithium battery of a mobile phone is 4.1 ~ 4.2 V when fully charged, and the available capacity is 4.2 x 40% = 1 .68 V, then the remaining value =
4.2-1.68 = 2.52 V, the phone will turn off automatically.
The large output current of the lithium battery causes a voltage drop. How to compensate for sampling?
We pGenerally understand that the minimum discharge voltage of lithium batteries is about 3.0V, and the minimum discharge voltage cannot be lower than 2.5V, otherwise it may cause permanent damage.
Actually, the discharge protection voltage of lithium batteries used in cell phones is set at around 3.4-3.6 V. The phone will automatically turn off when this voltage is reached .
The discharge characteristics of lithium batteries are similar to those of lead-acid batteries. As the power supply is discharged, the voltage across the terminals will continue to decrease. Additionally, there will also be a voltage drop across the internal resistance of the battery. Aging batteries will be more obvious and the charging voltage will drop significantly, disconnect charging then recover. If the battery is old, it is recommended to replace it. If the battery is new, it is recommendedto increase the load. battery capacity.