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My device has some loads which use 5V. I can't use a single Li-ion Battery as it'll give only 3.7V. So I've decided to connect the batteries in series to get 7.4V power supply. Since my wall adapter gives 12V output, I'm planning to use MCP73213 to charge the batteries. The batteries I've bought are actually cell phone batteries.

Now I've the following questions:

  1. Is it a good idea to use this cellphone batteries in series? Is there any possibility that this series connection will affect the battery life?
  2. Is MCP73213 a good choice, as it doesn't have any balance charging mechanism?

Battery Specification

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It depends on your application. If the batteries are charged slowly (<0.5C or so), discharged slowly (<0.5C or so) and operated at normal temperatures, balance is usually not a huge issue.

That said, it might be easier to just use a single cell battery and a switching boost converter to generate the 5V rail.

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  • \$\begingroup\$ Thanks for your reply. In fact, at first I tried to build a switching boost converter using LM2577-adj. But I failed for a mysterious reason, the output was always less than the input. I couldn't identify the problem, that's why I decided to use two cells. \$\endgroup\$
    – Arafat
    Commented Jan 10, 2018 at 5:27
  • \$\begingroup\$ Did you assemble the circuit on a solderless breadboard? That can be a problem for switching converters. With the popularity of USB power banks, there are lots of Lion -> 5V boost converter boards around that cost almost nothing. if you can't get one in your country, you can always cannibalize a USB power bank and use both the charger and boost converter from that. \$\endgroup\$
    – Dean Franks
    Commented Jan 10, 2018 at 6:12
  • \$\begingroup\$ Yes, I assembled the circuit on a solder-less breadboard. I'll give a try by soldering it on a Perfboard. And USB power bank boost circuit is also a good idea. \$\endgroup\$
    – Arafat
    Commented Jan 10, 2018 at 8:59
  • \$\begingroup\$ A perfboard is better, but even that can be a problem. If you are somewhere you can order from Amazon or any of the chinese vendors, get a module from them. Even though many of these boards are substandard from a design and manufacture perspective, they are probably better than something assembled on a perfboard. If you are going to assemble something on a perfboard, make sure you pay close attention to the high current loops in the boost converter, you have to do more than get just the right electrical connections. \$\endgroup\$
    – Dean Franks
    Commented Jan 10, 2018 at 17:14

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