Warning:

A Lithium Polymer battery, also called LiPo battery, can only be charged using a specific charger. It is even better that this charger has an integrated balancer, which equalizes the cells voltage between them during the charging process.
Every good charger in the market integrates actually a balancer.
The necessary settings for a safe LiPo charging can be found in the user manual of your charger.
It is very important to strictly follow the recommendations of the charger’s and the battery’s manufacturer.
During their use, the temperature of the LiPo batteries raises. Before re-charging them, they need to be left in a safe and dry place to cool down.
Beside the rare single cell units, the LiPo batteries are packs made of multiple internal cells. Each battery pack has a main power cable which is thick and ends by the main connector. There is also a secondary plug, called the balance connector which is wired to the battery with multiple thin cables that are linked directly to each individual cell.
Thanks to this wiring, each cell can be monitored during the charging process on an individual basis.

With a correctly tuned charger, the charging process of the LiPo will automatically end when the voltage reaches about 4,20V per cell.
If a LiPo battery is charged above 4,20 Volts per cell or with wrong charger settings there is a significant risk of fire or explosion.
The charging settings needed for a LiPo battery pack can be found in the manual of your charger and battery.

How to read the specifications inscription on a LiPo battery?

Example: 5000mAh / 14.8V / 4S1P / 20C / 4C Charge