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For a project, I want to charge a lipo battery (3.7V @2000mah) with a 5V USB charger. I'm not into electronics, so I don't know if is viable to do that.

So, can I charger a 3.7 battery with a 5V charger with no problems?

Thanks!

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  • \$\begingroup\$ Short answer: No, because your "5V USB Charger" is not a charger - it's a power supply. \$\endgroup\$
    – brhans
    Apr 14, 2016 at 19:06
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    \$\begingroup\$ No, you can not. You must read this: Safety Concerns with Li-ion. (There is a reason why R/C enthusiasts put Li batteries into flameproof bags, when they charge them.) \$\endgroup\$ Apr 14, 2016 at 19:09
  • \$\begingroup\$ @NickAlexeev Okay, I understand. So, in this case, how can I charge the 3'4V battery with that 5V charger? With a DC-DC? \$\endgroup\$
    – spund3
    Apr 14, 2016 at 19:25
  • \$\begingroup\$ @spund3 With a dedicated lithium polymer battery charger. To use anything else would be incredibly reckless and unsafe. Watch a few videos of poorly charged lipo failures and you'll understand why great care must be taken with lipos. \$\endgroup\$
    – uint128_t
    Apr 14, 2016 at 19:43
  • \$\begingroup\$ @uint128_t Okay. \$\endgroup\$
    – spund3
    Apr 14, 2016 at 20:07

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Ok, so you aren't actually asking the right question. I'm going to assume you mean you have a 5V power source (usb, battery pack, etc.) and want to charge a single cell lithium ion battery with nominal voltage of 3.6V or 3.7V.

Lithium Ion, also sometimes called Li-ion or Lithium polymer or Lipo) have a slightly different charger than other battery types. Typically, the charger supplies a constant current at slightly higher than the battery's voltage. As the battery voltage increases, the supplied voltage increases until it hits the maximum for the cell - typically 4.2V. Then, the voltage is kept constant and the current is reduced until it hits 3-5% and charging is considered done.

All of that is to say, that you need a specific charging circuit and an IC dedicated to charging a single cell lipo. You could build one, but that seems a little advanced for you at the moment. If you decide to, I detail my experiences here: https://thewanderingengineer.com/2016/01/27/simple-lipo-battery-charger-with-the-mcp73831/

A better option might be to buy a board that does this for you so that you just plug in a usb plug on one end and a single cell lipo on the other end and you don't have to worry about it. Here are links to a couple of products from sites that also have good tutorials about them: https://www.sparkfun.com/products/10401 https://www.sparkfun.com/products/12711
https://www.adafruit.com/products/259

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  • \$\begingroup\$ Oh thanks, that was useful! And also,ifI want to charge twi batteries at the same time, I have to connect them in parallel to the charger? \$\endgroup\$
    – spund3
    Apr 15, 2016 at 12:43
  • \$\begingroup\$ Charging two lipos is much much harder than charging a single lipo. You have to make sure that both cells are charging at the same rate. I'd just buy a lipo charger for that. \$\endgroup\$
    – mwwalk
    Apr 16, 2016 at 2:37
  • \$\begingroup\$ What if the battery you want to charge comes with a PCB on it already, with three wires? I assume the third wire is for reading battery status/level? My battery is this square one, 612338 size, that goes in my headphones. After replacing the battery twice without success (it will power the headset but not charge), I'm wondering if I can power it by applying 5V power from USB to the +/- wires on the PCB. The headset already uses USB to charge, but I think something's broken in the charging module. Do I need extra circuitry between USB and the battery PCB? Thanks :) \$\endgroup\$ Jul 30, 2023 at 10:10

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