1. The voltage when the cell phone is turned off should be around 3V and the normal voltage is 3V-4.2V. 2V will not be so low. After the battery is turned off and not charged for a year or two, it will not reach 0V. Although it discharges automatically, the cell phone battery has a protective plate. the voltage is too low or too high, the protection plate will play a role, which is a safety measure for mobile phone batteries.
2. Once the battery is fully charged, it will not continue to charge while the protective plate is in place. It is not suitable for use if the protection plate is present. The charger is not broken. It will explode, the battery will be fine and the cell phone will naturally have no problems either.
Nowadays, good cell phones use soft polymer batteries. At most, theywill only swell and burn, because the outer packaging is made of material. aluminum plastic film, most batteries are usually packaged in aluminum shells. The first batteries used steel hulls and the power of the explosion was still very high.