The charging method of lithium battery is voltage limiting constant current, which is controlled by IC chip, typical charging method is: first detect the voltage of the battery to be charged, if the voltage is lower than 3V, precharge first, charging current is 1\/10 of the set current, after the voltage rises to 3V, enter the standard charging process. The standard charging process is: constant current charging with the set current, when the battery voltage rises to 4.20V, it is changed to constant voltage charging, and the charging voltage is maintained at 4.20V. At this time, the charging current gradually decreases, and when the current drops to 1\/10 of the set charging current, the charging ends.
The USB output voltage of the computer is 5V, generally very accurate, the reason why we feel that the USB charge is not satisfied is because the USB output current is small, and the final stage of charging, you need to have a trickle charging. Trickle charging is used to make up for the loss of capacity caused by self-discharge after the battery is fully charged. After the battery is fully charged, the capacity lost due to self-discharge is about 5% of the nominal capacity. In theory, trickle charging should be at 1\/500 level of charging current, USB current is only 500mA, trickle is very small, so the process is very slow, you can't wait to pull it off, 5% is gone.
In addition, the lithium battery of mobile phone digital products has a protection board, which has the effect of limiting the minimum voltage and limiting the charging current. And now the mobile phone whether it is using a charger or a computer USB, is not that line, what to charge, only the difference between charging current, have to poke the \"butt\" of the mobile phone, as long as you use a USB cable to charge, what is on the other end, in principle, it is the same, only the problem of charging speed.
The laptop USB port charges the mobile phone, compared with the charger charging the bare mobile phone battery, the charging voltage is slightly higher (5V:4.2V), the charging current is slightly lower (190mA:220mA), but the desktop USB port, the charging voltage is still 5V, and the charging current rises to 230mA.
Comprehensive experimental results, the two charging methods are not significantly different, USB charging will leak or USB charging quality is not high, not durable argument is not scientific, the only difference is the length of charging time.