I have a project that the form factor of 18650 batteries works well for. The board I'm using is a esp32 based board with built in battery charging: https://www.amazon.com/gp/product/B072HBW53G/ref=ppx_yo_dt_b_asin_title_o00_s02?ie=UTF8&psc=1

  1. I've heard that the flatpack type Lithium Polymer batteries have built in over charge circuitry. Is this generally true?
  2. Can I directly charge a 18650 battery from Arduino type boards that have built in battery charging functionality?

EDIT: So from looking at the battery circuit schematic from the Wemos link and the board itself it uses a TP4054 "Standalone Linear Li-lon Battery Charger with Thermal Regulation in SOT". And since I can confirm the board works with 3.7V batteries and my 18650 is a 3.7V type I think I'm good.

EDIT: Found info on this board: http://www.raspberrypiwiki.com/index.php/WEMOS_ESP32_Board_with_OLED

Also by "Arduino type" boards I mean any popular micro controller board that has a battery charging function such as the Adafruit feather boards.

EDIT: To clarify: Reading here Li Poly and Li Ion batteries are essentially the same https://scottiestech.info/2015/06/21/lithium-polymer-vs-lithium-ion-batteries-whats-the-deal/

I believe the board is a Wemos D32 with an attached display though I can't find any specific info on this exact board. https://wiki.wemos.cc/products:d32:d32#technical_specs

I basically want to know if I can charge a Lithium Ion battery with this type of board. As this is potentially a safety concern I wanted to ask some experts.

  • The question in your title doesn't match the rest. The title ask about LiPo but the text asks about 18650s which are not LiPo. The answer to the question in your title is not if the built in charger is made for LiPo batteries and has overcharge protection. Can you add links to the actual schematics and specs for your board? My understanding is that LiPo and regulat LiOn charging have different requirements. What do you mean by Arduino type boards? The answers really come down to getting more specs for your board to tell what kind of charging it can do well.
    – T. M.
    Mar 17, 2019 at 1:18
  • Thanks for the feedback, I changed the title to something hopefully more descriptive and added some info.
    – Geordie
    Mar 17, 2019 at 3:43
  • I have the Lolin D32 pro, and my understanding of this document on TP4054 igotalongdomainname.com/data/uploads/tp4054-42pdf.pdf seems it have overcharge protection at least. Also since it claims it works with 3.7V batteries which is nominal voltage, it should work with the higher than 3.7V actual voltage that 18650 batteries have when fully charged. Also just for the record you can buy charge protection circuit boards for 18650 cells. youtube.com/watch?v=1rg3ZWxBNUE Do you have a jst connector to connect your 18650 cell to the board? If you try it, please update the post.
    – T. M.
    Mar 17, 2019 at 23:58

1 Answer 1


There are Lead based, Nickel-based and Lithium-based batteries (there are actually more, but these ones are the most popular). Each need a different charger, but since lithium polymer and lithium ion are in the same group, it should work but I don't have the option to test it out for you.

Q1: Not every battery has a built in over- and undercharge function. Some do, some don't. To find out if yours does, if the internet can't help, tear it apart (be extremely careful about it).

Q2: Depends what you mean by " built in battery charging functionality". If that includes the over- and undercharge functionality, then it will work (tested).

Looking at the board (https://wiki.wemos.cc/products:d32:d32#technical_specs) it seems doable.

The most important thing is to check, if the supported voltage of the li ion battery equals the supported voltage of the li polymer battery that can be charged with the li polymer charger. Since it says 3.7V on the data sheet, don't get a li ion battery with 3.7V+

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