The charging design of the battery is high current fast charge when low power, low current floating charge when close to full, 99% in the floating charge stage, it may take a long time to reach 100%, on the other hand, the mobile phone is determined by the voltage value of the charging state, the mobile phone battery design voltage 3.7V, charging voltage 5V, Generally speaking, when the voltage value reaches 4.2v, the phone considers the battery to be 100% full,
If the battery aging may be charged for a long time but can not reach the full set voltage, there will be a total charge is not satisfied, a situation of no electricity.
Mainly in order to protect the battery, so the ideal one charge is at most 97%, and the remaining 3% of the electricity can not be filled, of course, this is also related to the setting of the charging pile.