Sometimes, at certain percentages, the charging speed of your phone changes dramatically and drastically. Why does it feel like time moves fast when I charge my phone from 10% to 90%, but it seems to slow down to a crawl as it approach full charge? Here's the reason why:

To better understand why the speed changes, we need to know a little bit more about your phone's lithium battery charging.

The charging process of lithium batteries can be divided into four stages: Trickle Charge, Constant Current Charge, Constant Voltage Charge, and Charge Complete. At the beginning of charging, the phone will automatically check the battery voltage and set the charging current.

Stage 1：Low-current Charge

In order to protect the battery from getting damaged, it starts the charge with a small current. The longer the phone is charged, the stronger the current that flows through the charger. This is called Low-current charge.

Stage 2：Constant Current Charge

At the Constant Current stage, by increasing the charge current, HUAWEI Super Charge supplies the maximum current into battery to achieve fast charging. The charge current will stay constant until the battery reaches a certain voltage.

Stage 3：Constant Voltage

When the battery reaches a certain percentage (around 90%, varies per product), the phone will keep the battery volume unchanged, and gradually reduce the charging current.

If the current is not reduced, the Lithium-ion will be accumulated in the negative end of the battery and start to form a crystalike structure, which when grown big enough, will cause a short circuit by piercing the diaphragm between the negative end and positive end of the battery. Therefore, to keep the battery safe in the long run, the charging current will be lowered in this phase.

Stage 4：Charge Completed

When the phone screen displays that you have reached 100%, you can unplug the charger device.

This is the secret behind charging phones. Hope you find it useful.