The charger detects whether the battery is fully charged mainly through the following methods:

1、Voltage detection method

This is a relatively common detection method.During the charging process,the voltage of the battery will continuously rise.When the battery approaches a fully charged state,the voltage will reach a specific peak.The charger monitors the terminal voltage of the battery in real time through a built-in voltage detection circuit.Once the battery voltage reaches the preset full charge voltage value,the charger will determine that the battery is fully charged and stop charging.For example,for common lithium-ion batteries,their full charge voltage is generally around 4.2 volts.The charger continuously monitors the battery voltage and stops outputting current when it reaches this value.

2、Current detection method

In the initial charging stage,the battery can accept a larger charging current.As the charging process progresses,the battery gradually approaches a fully charged state,and its acceptable charging current will become smaller and smaller.The charger determines whether the battery is fully charged by detecting the magnitude of the charging current.When the charging current drops to a preset threshold,the charger considers the battery to be fully charged.This method can accurately determine the charging status of the battery,especially for large capacity batteries,which can effectively avoid overcharging.

3、Time control method

The charger pre-set a charging time based on the battery capacity and charging current.During the charging process,the charger charges according to the set time.When the charging time reaches the preset value,the charger will stop charging even if the battery may not be fully charged.This method is relatively simple,but its accuracy may be affected by factors such as battery aging and temperature.

4、Temperature detection method

The battery generates a certain amount of heat during the charging process,and the temperature gradually increases.When the battery is fully charged,the rate of temperature rise will slow down or reach a stable value.The charger detects temperature changes in the battery through a built-in temperature sensor.If the temperature change matches the characteristics of a fully charged state,the charger will determine that the battery is fully charged.However,this method requires consideration of factors such as environmental temperature to avoid misjudgment.

In summary,chargers usually use multiple methods to detect whether the battery is fully charged to ensure the effectiveness of charging.