Heltec WiFi LoRa 32 (V3) bluetooth high consumption - Board gets hot

I have been using Heltec WiFi LoRa 32 V2 boards for some time, with a sketch using LoRa, OLED and BLE, everything working fine.

The last boards we have bought are V3, so I migrated everything to the new version (board, libraries,…). I managed to make everything work in both board versions, but the power consumption is high in the V3 board and it gets hot, even if everything works fine (the heat seems to come from the area of the microcontroller).

I have narrowed the problem to the bluetooth, as the same happens using the “BLE_uart example” provided with the 0.0.7 board libraries. I have tried the example sketch with 3 different V3 boards and the same happens. But not in V2 boards.

Does anyone know anything about this?


Are you using the Arduino-esp32 support?

The V3 boards uses the ESP32-S3 variant. This issue https://github.com/espressif/arduino-esp32/issues/5909 says it impacts both the ESP32-C3 and ESP32-S3 chips. I had a high current/heating issue with a ESP32-C3 and setting the auto sleep mode in the Arduino-esp32 library fix it for me. Setting that option and rebuilding the library is not a trivial process.


Thansk for the info. I am ussing the libraries provided by Heltec (https://github.com/Heltec-Aaron-Lee/WiFi_Kit_series), and I can see in the sdkconfig for the esp32s3 that the sleep mode is not set either, as is the cause of the issue in the espressif library…

The info provided to recompile the libraries (espressif library builder) is only for the espressif libraries. I will try to find info about how to recompile any library, although I have never done such thing…

I will include this issue in the github for the heltec library.

Thanks agains.

I normally use Windows but for the lib builder had to work on a Ubuntu vm for the Arduino-esp32 lib build.

To save you some time:

  1. install IDF build environment first. Install v4.4.5 not anything higher. Arduino-esp not compatible with 5.x yet.
  2. when you get to lib builder ./build.sh -I v4.4.5 -t esp32s3

idf install https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/linux-macos-setup.html
lib builder https://docs.espressif.com/projects/arduino-esp32/en/latest/lib_builder.html
When the build is complete copy from the lib builder/out/tools/sdk to username\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.10\tools\sdk\esp32s3
that is where the Arduino IDE picks up the Arduino-esp32 “stuff” for the compile/link process.

I’m still investigating where Platformio gets the Arduino-esp from.

THank you very much, I will try that!


Hello Shernando,

I had to ensure the sleep time was properly setup. Not sure if this is your case.
I also have some troubles using heltec board. Would you be available to exchange some thoughts?

Do you use Discord?

Hello, Spaceway,

The truth is that, as I am currently in multiple projects and I still have some pieces of V2 boards, I have left this issue aside until I have the need to use V3, hoping Heltec solves this issue first.

In any case, I do not use Discord.


Hello Shernando,

Thanks for your reply.
I’m also using V2 board that I adapted the code to gather SDI-12 measurements and transmit them via LoRaWAN.

I’m having some issues to gather the measurements to the board, not sure if you had a similar issue but I’m having a hard time here to make this work. Could you give me a hand?


Hi, Paulo,

I do not really understand what you mean, but I guess that is another topic, not related to bluetooth, am I right?

Yes shernando, it’s not related to bluetooth transmission. I created a new topic here, could you give it a look? Really desperated to get some help :frowning: