I am running an HM-10 Bluetooth Low Energy (BLE) module to transmit serial data (using SoftwareSerial) from an analog sensor onboard my Arduino Uno to a serial terminal app on my Android phone. When I power the Arduino with a USB power bank, the data transmits flawlessly.

When I tried to power the Arduino with a 9V battery through the DC power jack instead of USB power, the BLE module connects to my phone, but no data is transmitted when a serial connection is established.

Any ideas why this would be?

  • "9V battery" as in little wimpy PP3 that can't power ****?
    – Majenko
    Commented May 30, 2017 at 15:11
  • @Majenko yes, correct. Is the implication of your reply that the (brand new) battery is not powerful enough? If so I could try to source a battery box to attempt to get it running on AA batteries as a test.
    – AggroCrag
    Commented May 30, 2017 at 15:38
  • 1
    In that case you would be better using Li-Ion batteries since they have a higher energy density for their size/weight.
    – Majenko
    Commented May 30, 2017 at 15:51
  • 1
    @Majenko - BLE transmit power is a brief pulse at a few tens of milliamps. It's within the capability of a CR2032 coin cell. Advertising fairly frequently mine drew an average of around 200 uA. Likely the Arduino draws more, at least on average. Commented May 30, 2017 at 22:58
  • 1
    Your whole line of reasoning here is based on a grossly erroneous guess at what these things draw. Check the TI data sheet if you don't want to believe me. Commented May 30, 2017 at 23:08

2 Answers 2


Take two 9 volt batteries with same specifications and connect it into the parallel by using this efficiency of current increases and it full fill the current requirement at the time of data transmission and for others modules u r using with the arduino.

  • While this likely wouldn't meet the OP's design requirements, it's a perfectly reasonable benchtop test to confirm that the 9v batter is (or isn't) the problem.
    – JRobert
    Commented Dec 3, 2023 at 13:31

A PP3 battery is not a suitable power source for an Arduino.

For battery powered operations I would recommend a set of AA batteries with between 6 and 8 volts (if you don't care about bulk) or a Li-Ion battery (or two) and a suitable buck or boost (depending on number of cells) regulator to bypass the inefficient linear regulators on the Arduino.


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