ESP8266 Node MCU powered by battery

Question

I am new to ESP8266 and started just building basic devices using it. However I am using USB 5V wall adapter as nodeMCU has USB UART converter to 3.3V.

If I want to make it battery powered what is simple , small ( in volume so that it can fit along with nodemcu and sensors in a small case) and economical approach that keeps my nodemcu still safe? -One option I can think of is to connect a Li-ion battery of 3.7V to VIN. -Another one is to use bigger voltage and use a converter to convert it down to around 5V and then use that to connect to VIN.

Please let me know if this works ? else if there is any better option please do suggest. Also if you are referring to any items/products please help give the exact model numbers so that I can search on internet to consider buying them.

Lastly I am not much aware of electric circuits & terminology yet ( learning them), so please help explain me in basic terms possible.

Ps: this question was seen on stackoverflow some times but I couldnt find one single consolidated answer and am confused by it. Appreciate your understanding.

Thanks, Sridhar.

Answer 1

This really would be better suited for the electronics sister site or a esp8266.com forum but for what it's wort here's my input.

IMHO the most convenient option you have is to buy a devkit with a LiPo connector. I recommend a WeMOS D1 mini plus a fitting battery shield. An alternative is the Adafruit Feather HUZZAH.

It can sometimes be a bit of a challenge to find the right connectors for those boards. Gotcha! different revisions of those boards might use different connectors. Currently the WeMOS battery shield uses a 2 pin JST PH 2.0mm.

Answer 2

No, you cannot power a NodeMCU using a 3.7v li-ion battery directly. A fully charged Li-ion battery outputs a voltage of 4.2v. The NodeMCU board has a (5v and above) vin slot along with two 3.6v slots. If you directly connect the battery to the 3.6v, it may fry the NodeMCU board. So typically, there are 3 ways you can connect the battery without frying your board in this scenario:

1. You can use a boost converter to convert the 4.2v output to 5v. Then connect it to vin. This will draw more current and battery discharges quickly (eg: MT3608 step up boost converter).
2. You can use a buck converter to convert the 4.2v to a steady 3.6v (eg: LM2596 step down converter).
3. Finally, the most efficient way is to connect a 3.3v LDO in middle. The difference between using a buck and LDO is, buck provides a constant and steady 3.6v output, where as LDO's output depends on the input voltage from battery (eg: S111733PI).