We are completely familiar with the fact that Lithium Polymer Batteries contains great power in a small package. But they are designed in a manner which is considered tricky in order to charge securely. In a tutorial of Adafruit LiPo Chargers project, a charging cycle is designed for safely charging 3.7v Lithium Polymer cells.
This project aims to design the batteries that can adjust more than 3.7v. But forcing more voltage into a multi-cell pack is dangerous. Therefore, Adafruit has come up with another tutorial that shows how to safely charge multiple cells while maintaining a balanced charge.
The products used here is based on the tutorial of USB / DC LiPo Charger or USB LiPo Charger V1.2.
The simple balance charger guarantees that the cells remain ‘balanced’ every time while charging them in parallel. Here, once the cells are attached in parallel, the variances in charge level is equalized and they act as a solo cell to the charger. This circuit will function with the USB / DC LiPo Charger or the USB LiPo Charger V1.2.
Multi-Cell LiPo Charging (Image Courtesy: adafruit)
The above conditions can work only when the cells are disconnected from the load with the help of a 3-pole double-throw switch. And again the charger is connected and the cells are switched from series to a parallel configuration. Further, the charger output can be occupied from any of the battery terminals via soldered connection or a JST connector.
The cells, in charging mode, are joined in parallel to the BATTERY IN terminals of the charger while the positive side of the Load output is detached during the charge. Further, in run mode, the positive connection to the BATTERY IN terminal is disengaged and the batteries are connected again into a series configuration.