The day before I got my used full package arduino uno. I tested it on USB plug. Everything worked fine. I wrote a piece of testing code and uploaded. After I have accomplished with the test I have unpluged arduino from PC and connected to battery and I see that it does not work. I have used a multi-tester to find out the voltage. It showed 4.7V. Now I wonder should I buy a new battery or there is another reason for this. Anybody, please suggest me what to do. Update The battery came with arduino set. It is written that it is a 9V battery. I am plugging it to the battery input in my arduino uno. Polarity is ok. The same program working on connection via usb, does not when connected to battery.

  • 2
    What kind of battery? How did you connect the battery to the Arduino? Did you check the polarity? – Edgar Bonet Jun 16 '15 at 13:36
  • @EdgarBonet updated by question. – iamawebgeek Jun 16 '15 at 15:38
  • Do you read 4.7 V between "Vin" and "GND" or between "5V" and "GND"? Does the "ON" LED light up? – Edgar Bonet Jun 16 '15 at 15:41
  • @EdgarBonet I think I got the point, the "ON" ligth has not turned on. So it means that the power supplied by battery is not enough to run the arduino? – iamawebgeek Jun 16 '15 at 15:45
  • What does your DMM say? – Ignacio Vazquez-Abrams Jun 16 '15 at 15:51

Did you make sure the battery is charged? Does it have enough voltage to power the board? Remember that Arduino has internal voltage regulator, so you need something little more than 5V in order to get it working okay.

(Comment by bpinhosilva re-purposed as an answer so this will stop showing up as unanswered).

@bpinhosilva you are right, the battery was not supplying enough power to make arduino work.

Please accept this so that the number of unanswered questions goes down. :)


Check the serial number of your board. Some boards were shipped with a defective boot loader, which has the loader stuck in an infinite loop when powered off and on again. Just Google the serial range of possible defective boards, and check if your board is in that range.


Try to use a battery that provides at least 7-12 volts. The voltage regulator will regulate the needed 5 volts for the arduino.


simply you can weld a little electrolytic capacitor eg. 4 or 6 microfarads, 12 or more Volts, with the positive wire on the reset pin and the negative on the GND pin. in this way you can solve the restart without the USB connection. This is what I did Enjoy with Arduino. By Daniele

  • This seems to address a different issue :) – Dave Newton Jun 11 at 14:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.