Thanks. Team effort!
I also installed a 3.5v 500mah lipo battery pack (without causing a fire this time).
Battery seems to work at the start, but then encounters a problem:
It runs the leds and sound at the same level as USB power, but when the loop reaches the point to "attach servo", it pauses, blinks, and restarts the loop again from the beginning. It does not attach the servo and finish the loop.
People run a servo on 4 AA batteries. Could it be I don't have enough mah? The volts shouldn't matter because the board adjusts to 5v anyway.