9 Volt Battery Adapter for Arduino




This is super simple but very useful if you are in a hurry or just like to do things yourself and on the off chance you didn't know, this is about the easiest way to add mobile power to your Arduino. 

After looking at a number of battery power solutions for Arduino ranging from Lithium Backpacks to Minty Boost kits I decided I didn't want something even that complicated. Granted, the 9 Volt isn't the most efficient battery for the job and it's expensive compared to others, but it is widely available and compact. 

It is also possible to wire a battery adapter directly to the pins but I wanted to use the DC power jack and not have any wires running to the pins than I have to. 

I did this for my Mega but it should work with any of the Arduino boards with a 2.1mm jack. You can use either the 2.1 X 5 or the 2.1 X 5.5, both will fit. 9V DC is right in the middle of the ideal range for the on board power management circuitl. So, no resistors, caps or other components are needed. (They are rated up to 12V but I don't think I'm brave enough to test it with a Mega since you can't just replace the chip if you cook it.) 

You can buy these assembled from Adafruit  but I needed a couple of them and didn't want to wait for the mail or pay shipping. You only save a few dollars but you get to do it yourself and you have the option of extending the leads if you need to. 

Step 1: Materials

1 9V battery snap connector
1 Coaxial plug 5X2.1(K) size is probably best but the 5.5X2.1(M) will also work
A couple inches of 1/8 inch shrink tube and an inch or two of 1/16 inch

A few inches of 27 X 1 3/8 inner tube. The 1 3/8 is the important part
An inch or two of Velcro


Soldering iron and solder
Wire cutters
Hobby knife or scissors

Step 2: Solder the Positive Lead

The positive lead is the center contact for the Arduino. 

Slip a small piece of 1/8 shrink tube over both wires and another 1/16 one over the positive wire and slide them back while you solder. (If you want to use the protective cover that came with the plug you can do that as well. I used both shrink tube and the plastic cover.) 

Solder the red wire to the small pin/center lead and let it cool before pushing the shrink tube in place. Be sure to push the shrink tube as far up as it will go to prevent shorting. 

Step 3: Solder the Negative Lead and Wrap It Up

Solder the black wire to the larger outside lead of the barrel plug. 

After the solder cools you can slide the larger shrink tube (and or the plastic cover) and shrink it.

Essentially you are finished and ready to attach your 9V battery.

It would be wise to check your plug with a meter to ensure you haven't shorted anything. 

Step 4: Optional Battery Cover Velcro Mount

This is an ultra simple extra for an already simple project. Might as well give it a go. 

Simply slip fit a section of the inner tube over your 9V battery and trim it to length. 

Then attach a section of self adhesive Velcro. You likely want to attach the hard side to the battery cover and the soft to whatever you'd like to mount it to. 

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    15 Discussions


    6 years ago

    How long does the battery power the mega for? Is it hours or minutes?

    1 reply

    Reply 6 years ago

    Seems to be hours for most things and wiring power directly to the board doesnt seem to make a difference either way on power consumption.

    I am extremely new to this field, and I am really whipping myself up into a frenzy about it - buying all kinds of motors and tiny components, etc. I'm pumped. Anyway, I really wanted to free myself from the USB/wall cord, so I went ahead and made this simple 9v battery pack based off this instructable. I might also add that this was my first time soldering. It really turned out pretty well, although I couldn't get the heat-shrinking tubing to . . . shrink. Pointed a hair dryer at it for a hot minute to no effect.

    2 replies

    If the hairdryer is on high and you hold it very close it should work. If the air hot enough to burn your fingers it should be hot enough. I use a space heater! XD

    Yeah, i made the instructable because it's dead simple and useful to a beginner but not something advanced users and guides seem to bother telling, it's just an after thought for a lot of people. so, i'm glad it was helpful.

    I don't think a hair dryer will get hot enough, even after a while, to shrink the tubing. Most people i know use a lighter or soldering iron. Just be sure to keep your heat source moving so as to shrink and not burn the tubing.

    Good luck with your projects!


    7 years ago on Introduction

    just FIY, if you have an Energizer battery you can open it up and use the little top piece for a connector. Energizer batteries have little AAAA batteries inside so you dont have to worry about acid. just solder the wire to the little disks and pop it on a fresh battery. i have done this a couple times. (it might be possible to use any other type of battery as long as you are careful and you don't break open the inner "ACID CONTAINMENT UNIT".) lol BE SAFE.


    8 years ago on Introduction

    9V is certainly quite usable for arduino boards. I think they suggest not using anything more than 12V.

    I have to ask a question though, why wouldn't you just insert wires into Vin and Gnd? You still need the 9V snap thing though.

    1 reply

    Reply 8 years ago on Introduction

    Yes, the data sheet says 7.5V-12V for the smaller Arduino's and 6.5V-12V for the Mega as it has a lower voltage drop off in the power management circuit. Less than the bottom end numbers and you won't get the needed 5V to the board due to the drop off. This isn't an issue when using the USB.

    I wish the manufacturers made this information more clear. It's a lot easier to power Arduino's than it at first seems. Especially when people are building all manner of things from solar chargers to Minty Boost kits for that. Those are great but this is far more simple, fast and easy if you don't want to go that way. My only improvement will be adding a Joule thief circuit once I make sure it won't cook the board or be underpowered. Shouldn't be an issue, I just haven't gotten to it yet.

    There were two reasons I didn't wire directly to the pins;

    I wanted to keep the it as clean as possible and didn't want wires running to the pins when a nice clean plug was available. It's also easier to disconnect when I'm running the Arduiono through the USB.

    I also have more than one Arduino and liked the option of switching the adapter between them if one breaks or I only have on on hand.

    Ultimately it's an extra $.99 component and makes for a better build for my needs. In a robot, or some other more permanent application, I think wiring direct to VIN and Gnd as well as removing the socket could be useful.


    8 years ago on Introduction

    Thank you for this i was needing it I'm new usinr arduinos :)


    Reply 8 years ago on Introduction

    You certainly can. It's very simple and would be an inexpensive and easy introduction to soldering if you haven't done so! Feel free to PM me if you need any help.


    Reply 8 years ago on Introduction

    I know this is dead simple but I was how few people knew about it. It took a little digging to find out what the on board power management circuit could handle. Basically the ability to just plug in a 9V battery like this is implied on the Arduino data sheets but not explicitly stated.

    So again, while admittedly super simple it's useful and I thought it worth sharing for those that might not know. It's also a heck of a lot more compact than a minty boost.



    Reply 8 years ago on Introduction

    Lol, highly unlikely indeed. Just wanted to post it separately from the arduino Morse code transponder it powers.