Hello Denis,
We don’t make a Baby-O that runs at 3.7 V. At least one person has had success modifying their Baby Orangutan to run at 3.7 V. Here is a forum thread about it: https://forum.pololu.com/t/babyo-single-lipo-cell-fuse-settings-revisited/1141/1.
Here is a summary: you have to change the AVR to use its internal 8 MHz clock instead of the 20 MHz external oscillator. You will also need to lower the brownout detection voltage from 4.3 V to 2.7 V or disable it. You can choose to power the BabyO through Vcc directly, bypassing the voltage regulator.
Please note that certain functions in the Pololu AVR library depend on the AVR running at 20 MHz. So be careful about which library functions you use.
- Ryan