Hi there ,
I'm building a 3 inch toothpick to fly with 2S 18650 Li-Ion. The Flight Controller I put in is HIFIONRC F7 AIO 45A with preinstalled BLHELI_S [GH30] ESC STM32F722. The problem is I have a Low Voltage Cutoff on 3,5 V per cell with this BLHELI_S. The question is how to overcome this without changing the board? The MCU is STM32F722 so maybe it's compatible with BLHeli_32 where I can turn off LVC? If yes how to safely flash BLHeli_32 to this?

 Link to the HIFIONRC AIO FC

You can't flash BLHeli_32 firmware to BLHeli_S ESC's. BLHeli_32 is licensed firmware and the MCU's for the ESCs have a licensed bootloader which is flashed at the factory, so you can't do this yourself. Some people have bypassed the voltage regulator on BLHeli_S ESCs to prevent the low voltage cut-off. See the following threads for more details...

• https://intofpv.com/t-li-ion-18650-batte...age-cutoff
  
• https://intofpv.com/t-voltage-regulator-...blem-on-2s
  

Hi Snowball,

You are in luck by using the HIFIONRC F7 board; The link below is a hardware "mod" that bypasses the low voltage regulator which is used for low voltage cutoff.

>>  [ESC]   2s li-ion discharge trick           <<<  Thanks to Joshua_A


CAUTION:  This is a hardware modification which requires decent soldering skills; 
                    Use at your own Risk.

Thank You for the replies. Hardware mod is very interesting.