# Designing a 2S Li-ion charger with 5V 2A input

I'm interested in designing a few similar charging circuits based on the specs of the title which is getting a charging for 2 cells in series(or more) from a 5V input.

Now my question is:

Assuming I can easily boost the voltage up what should I consider in the actual charging circuit in term of max safety?(Assumming I also have a BMS installed in this pack) and having other useful example circuits for multi cell charging would also be useful.

Thanks for helping!

Assuming I can easily boost the voltage up what should I consider in the actual charging circuit

You should consider offers from Texas Instruments, Maxim Integrated, or Analog Devices, and few other companies, who offer a lineup of chargers (battery management ICs), and use their design tools to select the best match for your project. They would have many "useful example circuits".

The assumption about "easily boost the voltage" is most likely wrong.

• Any actual circuit and explanation of such a thing for example for 2S battery charging at 5V 2A? I'd like to know what charging properties should it have and if special whether to control it digitally or analog ally – Michael Aug 14 '18 at 11:56
• @Michael, had you any chance to follow links that I provided? I know for sure that some TI charger ICs do provide a limit on input current if programmed properly over I2C, to meet your 5V2A input limit. – Ale..chenski Aug 14 '18 at 18:11
• Too advanced I don't want to use any digital components at all in there also those don't give any explanations on what a proper safe li-ion battery charging should contain in term of characteristics. – Michael Aug 15 '18 at 1:02
• @Michael, then probably you should start with some entry-level educational articles, like batteryuniversity, batteryuniversity.com/index.php/learn/article/… – Ale..chenski Aug 15 '18 at 1:32
• Ok that gets me a little close just looking at the graph and understanding that you need to charge it at constant current and when the cell reaches 4.2V switch to constant voltage charging but how should it practically be achieved? using an opamp? something with a transistor or a zener diode? I need a practical real life direction! – Michael Aug 15 '18 at 21:59