The cell phone battery has three contacts, which are positive, negative and identification resistance contacts.
An identification resistance contact in the middle of the cell phone battery. When the phone power display is wrong, the phone battery will be repaired with a change electrode. The extra electrode of the mobile phone battery is the detection pole on the battery protection board, which is used to detect the status of the battery and facilitate the automatic protection of the battery and the mobile phone.
The third contact is also the battery data interface, such as temperature data, but also the transmission of battery charging and discharging data. If the user uses universal charging, it is also necessary to pay attention to not connecting the wrong contact.
Different manufacturers may be different, but the most likely is a thermistor, used for mobile phones or charger to monitor the temperature of the battery, you can try to use a multimeter to measure the resistance value at different temperatures. If it is just for charging, regardless of this contact, only connect the positive and negative terminals.
Generally, there are three contacts, in addition to the positive and negative electrodes, and one is a detection pole, which is used to distinguish whether the original battery, or to detect the temperature of the battery cell, and can control the charger to stop charging when the temperature is too high.
Most cell phone batteries have three metal shocks, which are positive, negative and identification resistance contacts.
< br >
In addition, there are some mobile phone batteries today that have four metal contacts, such as HTC's mobile phone battery. The contact on the battery is a negative temperature coefficient thermistor, which is also on the battery protection board to suppress excessive current in the circuit and protect the mobile phone battery. In short, it is the mobile phone battery has added some protection modules, so there are three or four contacts.