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Designing Constant Current and Constant Voltage Source for Single Cell Li-ion Battery Charger (Part- 4/17)




I have a 11.1v 4400mah battery in 3s2p configuration .I need to charge a battery with cc and cv mode using LM317 IC with automatically switching from cc to cv mode when it is needed.I have a smps of 12v ,2a. So how can I make circuit after smps?First I need to increase smps voltage from 12v to near around 13 because battery's peak voltage is 12.6 v when it is fully charged. So how can i make 12v to 13v?And secondly CC and CV circuit with LM317 and auto switching from cc to cv with indication?

Please help me on this...


What is the chemistry of the battery ?

Hello Sham,

As you want to charge a Li-ion battery pack whose excited voltage is 12.6V and nominal voltage is 11.1V. But you have only 12V DC supply. So here you have two queries first how to increase the DC voltage and second to use an automatic switching and battery indication. In the above experiment you can read about automatic switching with battery indication. So please read the above experiment carefully for your second query.

Now regarding your first query (step up the SMPS voltage) you can do two things

1. The excited voltage of the Li-ion battery is its maximum voltage, it is recommended to charge a Li-ion battery below its  excited voltage. So it is fine if you charge the battery at 12V for better battery life. But if you want to charge the battery at its maximum excited voltage.Then you can read the second point 

2. For stepping up the DC votage to higher voltage there are following methods

   i. First way is to use a "Voltage Doubler Circuit" 

   ii. Second you can use a Boost converter IC like XL6009 or you can make a simple boost converter circuit using some                 inductors and capacitors. Boost converter is a DC to DC converter which step up your input DC voltage to a higher voltage.

You can find Voltage Doubler circuit, Simple Boost converter circuit and XL6009 IC circuit (Experiment named - Power bank) here at engineers garage website. So please refer them. Even though if you have any query then please feel free to ask. I hope this will help you in your design.

i am Gayathri , 
i have a Tech Fest in my college. so i need to implement ELECTRONIC'S AND COMMUNICATION based  project.
i will be pleased if u suggest me easy project implement .