# Thing Plus using BluetoothSerial doesn't work under battery power **URL:** \ **Category:** Arduino\ **Created:** [June 14, 2022, 6:28pm UTC](https://community.sparkfun.com/t/thing-plus-using-bluetoothserial-doesnt-work-under-battery-power/44081 "2022-06-14T18:28:12Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Bushedo](https://avatars.discourse-cdn.com/v4/letter/b/45deac/32.png) [@Bushedo](https://community.sparkfun.com/u/Bushedo)\ **Post date:** [June 14, 2022, 6:28pm UTC](https://community.sparkfun.com/t/thing-plus-using-bluetoothserial-doesnt-work-under-battery-power/44081/1 "2022-06-14T18:28:12Z")
The board is actually a Thing Plus C and while the bluetooth works will connected to the USB of my computer, it doesn’t work under power from a LiPo 1S battery (18650) input through the Vbat pin of the thing. I can get BT connection when connected to USB, but if I disconnect USB while battery is connected the BT also disconnects. If I start only under battery power, the Bluetooth fails to connect. I have another Thing Plus C that runs off a LiPo and the BT works perfectly. The main differences between the two projects are the number of extra modules on the problem system. It has a BMP280, Ublox GPS, 9 DOF IMU/Mag sensor, realtime clock and DS18b20 temp sensor. Not sure if problems are related, however I did notice that onboard voltage regulator was unable to supply enough current to run all the boards. Voltage dropped below 3v. Had to augment power with the battery to get GPS working. Have capacitors across power inputs to damp voltage spikes. Would like to know if anyone has any ideas where the problem might lie. Did not want to post the code as it is over 400 lines and the BT sections are pretty much the same as the other working project. Thanks in advance. ---
**Author:** ![TS-Russell](https://yyz1.discourse-cdn.com/sparkfun/user_avatar/community.sparkfun.com/ts-russell/32/6092_2.png) [@TS-Russell](https://community.sparkfun.com/u/TS-Russell)\ **Post date:** [June 14, 2022, 6:44pm UTC](https://community.sparkfun.com/t/thing-plus-using-bluetoothserial-doesnt-work-under-battery-power/44081/2 "2022-06-14T18:44:08Z")
The system is over-drawing the discharge amperage the battery can provide; using a larger mAh battery, a higher-voltage/amperage battery with a stepdown converter to bring the voltage down to MCU-compatible levels, or try using a 2nd battery to directly power the additional sensors ---
**Author:** ![Bushedo](https://avatars.discourse-cdn.com/v4/letter/b/45deac/32.png) [@Bushedo](https://community.sparkfun.com/u/Bushedo)\ **Post date:** [June 14, 2022, 9:52pm UTC](https://community.sparkfun.com/t/thing-plus-using-bluetoothserial-doesnt-work-under-battery-power/44081/3 "2022-06-14T21:52:36Z")
Thanks for the input, but the voltage drop occurred when I was running strictly off USB power. With the battery the voltage has been steady 3.6V. ---
**Author:** ![Bushedo](https://avatars.discourse-cdn.com/v4/letter/b/45deac/32.png) [@Bushedo](https://community.sparkfun.com/u/Bushedo)\ **Post date:** [June 16, 2022, 6:54pm UTC](https://community.sparkfun.com/t/thing-plus-using-bluetoothserial-doesnt-work-under-battery-power/44081/4 "2022-06-16T18:54:26Z")
I now believe the issue was caused by brownout from the USB supplied power from the desktop. I used another 5V source and supplied it to the V\_USB port without connecting the USB cable to the computer. I had the battery supplying power to all the auxiliary boards separately. Everything worked as expected. Then tried using the 5v USB input pin and supplying the other modules through the 3.3V output of the Thing board. That also worked without problem. ---
**Author:** ![Bushedo](https://avatars.discourse-cdn.com/v4/letter/b/45deac/32.png) [@Bushedo](https://community.sparkfun.com/u/Bushedo)\ **Post date:** [June 16, 2022, 8:22pm UTC](https://community.sparkfun.com/t/thing-plus-using-bluetoothserial-doesnt-work-under-battery-power/44081/5 "2022-06-16T20:22:42Z")
If anyone from Sparkfun reads this I would like to know why running on battery power alone caused a problem. The 5V power supply I used to successfully power this project was limited to 700 mA or about 3.5 watts. I think it unlikely the 18650 battery I was using couldn’t match this. Perhaps there is some other limiting factor in the power system regulator?