1. Zero voltage battery or zero voltage battery in the battery pack;
2. The battery pack connection is incorrect, and there are abnormalities in the internal electronic components and protection circuits;
3. Charging equipment malfunction, no output current;
4. External factors lead to low charging efficiency (such as extremely low or high temperatures).

1. The battery is subjected to external short circuit or overcharging, reverse charging (forced overdischarging);
2. The battery is subjected to high rate and high current continuous overcharging, causing the battery core to expand and the positive electrode to directly contact and short-circuit;
3. Internal short circuit or micro short circuit of the battery, such as burrs penetrating through the separator paper and causing short circuit between the positive and negative electrode pieces, improper placement of the positive and negative electrode pieces causing short circuit between the electrode pieces, or short circuit between the positive electrode piece and the steel shell, negative electrode dropping into the separator paper, defects in the separator paper itself, and short circuit between the positive electrode tab and the negative electrode piece.

Because at the termination of the constant current process, the electrochemical polarization inside the battery remains at the same level throughout the constant current. During the constant voltage process, the concentration polarization of lithium ions inside is gradually eliminated under the action of a constant electric field, and the migration number and velocity of ions are manifested as a gradual decrease in current.

According to convention and the design of cordless phones, they should be returned to the base after each use. This can activate the phone, replenish the released capacity, and compensate for the capacity loss due to self discharge. However, we recommend occasionally fully discharging the battery to restore its initial capacity and discharge performance. Of course, if the phone is not used for a long time, it is best to remove the cordless phone to avoid the battery being overcharged for a long time. In addition, even after the cordless phone is turned off, there is still a small amount of current discharging in the system. Therefore, when not in use for a long time, the battery should be removed and placed in an open circuit, and recharged when in use.

In fact, the inability to power on is mostly not a problem with the battery itself, but rather due to overcharging and overdischarging that occur during battery use, causing battery circuit protection and cutting off battery output. The key to avoiding such problems is to avoid long-term charging, use batteries that automatically shut down, avoid repeated forced power on, and charge them in a timely manner.