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Will Nodemcu support 4AAA batteries which is 6v approx, or should i go with 3AAA batteries which is 4.5V approx. And one more question , is it ok to use AA instead of AAA ?

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Yes, yes and yes.

Will Nodemcu support 4AAA batteries which is 6v approx

Yes, it will. However there is no back-powering protection on the USB, so having that connected whilst the board is connected to your computer could potentially damage your computer's USB port. That's why VIN's label was changed to 5V on the newer boards.

or should i go with 3AAA batteries which is 4.5V approx.

Yes, you should. Not only does that mean your USB port won't die, but you're not wasting as much power. The NodeMCU employs a linear "LDO" regulator to get 3.3V from the incoming power source. That means that the voltage difference between incoming power and 3.3V is thrown away as heat. The higher the incoming voltage the more heat is generated to discard that voltage. Using a lower voltage, therefore, means that you don't waste as much. That fourth battery is doing absolutely nothing towards powering your project and is just being used to generate more heat. One thing to note though is that 5V coming in from USB could try and charge your 3xAAA batteries. If they're not rechargeable then they could cause problems (overheat, leak, cause a fire, etc). Adding a schottky diode in series with them would protect them from that.

is it ok to use AA instead of AAA ?

Yes. Your project will last longer before you need to replace the batteries, since AA batteries have a higher mAh capacity than AAA.

  • Thanks. How long do you think 3 AAA battery can last before replacing, approximately? Im connecting only one soil moisture sensor to the nodemcu. – Prashant Gokul May 16 '18 at 11:02
  • I can't tell you that. – Majenko May 16 '18 at 11:03
  • Can you suggest me someway , that the board gets power for atleast a month? I tried 9V battery, and conncted the positive and negative to Vin and Gnd. The board started working abnormally. I guess 9V battery is overloading the board – Prashant Gokul May 16 '18 at 11:05
  • It is impossible to give any value. It all depends on your code and your hardware. To get that kind of length of operation of AAA batteries you will need to use some very aggressive power saving techniques (deep sleep modes, high efficiency regulators, isolated power domains, etc). – Majenko May 16 '18 at 11:07
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    And 9V batteries are complete junk. – Majenko May 16 '18 at 11:07

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