The Baby Orangutan can be run on 3V lithium cells after a small hardware modification. In fact, all elements run down to very low voltage levels, except transistor Q1 (I530A), which serves as a polarity reversal protection. Q1 noteworthy progressively closes at potentials below 4.7V.
The solution consists in shorting out Q1 by practicing a tiny solder bridge between pins 4 and 5 of the I530A under a binoculary loupe (if the Baby-O circuit board is placed with Q1 at the top right, the upper row pins of Q1 are 1, 2, 3, and its lower row pins 4, 5, 6 from left to right).
Further to this, the brown-out level must be set to 2.7V and the clock speed to 8 MHz (i.e. to the internal oscillator). The programming speed must be lowered, too:
In the Atmel Studio 6 Device programming tool, read in the device data (Baby Orangutan connected to the ISP programming device and powered up), then:
Under “Interface Settings” set the ISP Clock to 460.8 kHz;
Under “Fuses”, set the oscillator SUT_CKSEL to
INTRCOSC_8MHz_6CK_14CK_4MS1 (select from table)
Under “Fuses”, set the “brown-out” detection level
BODLEVEL to 2.7 V (select from table)
then program the fuses by clicking “program”.
All timing routines are now slower by a factor 0.4, but the Baby-O runs on normal Li-cells