7.4V Two Step Lithium Battery Charger Circuit - CC and CV mode

The advancement in Electric Vehicles, Drone and other mobile electronics like IoT Devices seems to be promising for the future. One common thing among all these is that they are all powered by batteries. Following Moore’s law the electronic devices tend to become smaller and more potable, these portable devices should have their own source of power to operate. The most common battery choice for portable electronics today is Lithium Ion or Lithium Polymer Batteries. While these Batteries have a very good charge density they are chemically unstable under harsh conditions hence care should be taken while charging them and using them.

In this project we will build a Two Stage Battery charger (CC and CV) that could be used as to charge Lithium ion or lithium polymer batters. The battery charger circuit is designed for 7.4V lithium battery pack (two 18650 in Series) which I commonly use in most robotics project but the circuit can be easily modified to fit in lower or slightly higher battery Packs like to build 3.7 lithium battery charger or 12v lithium ion battery Charger. As you might know there are ready made Chargers available for these batteries, but those that are cheap are very slow and those that are fast are very expensive. So in this circuit I decided to build a simple crude charger with LM317 ICs with CC and CV mode. Also, what’s more fun than building your own gadget and learning in it’s process.

Remember that Lithium batteries should be handled carefully. Overcharging it or Shorting it might lead to explosion and fire hazard, so stay safe around it. If you are completely new to lithium batteries then I would strongly advise you to read through the Lithium battery article, before proceeding further. That being said let’s get into the project.”


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