18650 3.7V 3800MAH Blue Li-ion Rechargeable Lithium Battery for Arduino

Hi everyone! I am using both Arduino Uno and Mega for my project, I use 9V batteries as power sources, but it gets overheat over a period of time. Then I found out Li-ion batteries is other option for that. I am not sure how many units of the batteries needed per Arduino board, and can be used for both Uno and Mega?
Thanks for answering my question in advanced!

Post a picture of that type of battery. Does the battery overheat?

I have used 18650 batteries with these charger/boost modules to power stand alone type Uno boards that I made. Adjust the output to 5V for Uno, Nano, Mega and connect to the 5V pin.

Hi, the battery does not overheat but the board itself, because the data I got from the board is messed up over a period of time.

@stephanie9 Both boards have "Input Voltage (recommended) of 7-12V, so you can use two 3.7V 2500mA lipo batteries wired in series to power both.

Hi, so one unit of the 3.7V battery is enough for both Uno and Mega?

What on the board is getting hot? The voltage regulator? The processor chip? What else is powered by the 5V regulator on the board? How are the 9V batteries connected to the Arduinos?

Take care when powering the Arduino through the Vin or the power jack. Powering through Vin or the power jack means that the Arduino and all peripherals that are on the 5V rail are powered by the onboard 5V regulator. The on board 5V regulator is not heat sinked so will supply limited current before it overheats and shuts down. I would use a buck converter to drop the 9V to 5V and connect that to the 5V on the Arduino, bypassing the, weak, 5V regulator. Then the rated current of the DC DC converter is available on the 5V line.

U mean put two 3.7V in series right? Then it will be 7.4 V in total. But I am not sure if the board will get the overheat issue as well. That's why I wonder if there is anyone here have similar case before..

It is just my guess actually because it gets overheat over a period of time whenever I supply it with 9V battery. But when I connect it with my laptop, It works totally fine and even faster response. FYI, I am connecting the 9V batteries through power jack..

When you power with the laptop you are using USB power and the, weak, onboard 5V regulator is bypassed. When you power with anything connected to the power jack, everything that is connected to 5V is powered by the, weak, 5V regulator. If you do not want to overheat, don't use the weak on board 5V regulator, use a battery capable of supplying the required current and an appropriate buck or boost converter and connect to the 5V pin.

So you mean I should connect it with battery through the USB port?

No the battery does not connect to the USB port.

Connect the battery to an appropriate buck or boost module. A 3.7V battery will need a boost converter (3.7V to 5V). A 7.4V (or more) battery will need a buck converter (7.4V - xV to 5V). Connect the output of the converter (5V) to the 5V pin.

if connects the battery to 5V pin, means it will bypass the regulator as well?

Yes that would bypass the onboard regulator, but do you have a 5V battery? If you connect a 3.7V battery to the 5V pin of an Uno or Mega it probably will not run as the voltage is too low. If you connect a battery of more than 5.5V to the 5V pin you will very likely burn the Uno or Mega.

And any battery will not have a steady output. They will be high when fully charged and the voltage will drop off as the battery discharges. A buck or boost converter will compensate for that and try to keep the voltage steady throughout the life of the battery.
So, along with the battery you need the converter to keep the power supply voltage near 5V for an Uno or Mega.

You also need to keep in mind how much current your project requires. Your batteries need sufficient current capacity to run the project for the for the time between battery charges or replacement. Capacity is stated in mAH or milliamp hours (the average current per unit time multiplied by the time between charges).

I see..Thanks for the help!

@stephanie9 one 3.7V lipo battery is not enough for VIN-GND input, input must be within 7-12V recommended. 5V supply input if you are powering it via the USB.

Hi! I am planning to provide 5V output from battery to Arduino via USB cable, thanks anyway!