I'm using arduino fio to control a circuit using 2 piezo and 2 tri-LED. This fio communicates with other 2 fios via xbee. When I used the Polymer Lithium Ion Battery 3.7V connected to BAT+/- pins to supply for the arduino (connected to the circuit and no Xbee yet) the output at 3V3 pin dropped downto 0.7V. My circuit requires around 3V power supply at some points. Can someone tell me why the voltage dropped so much? How I can improve it? Should I connect higher voltage supply into BAT pins and how much should I connect or should I connect directly power supply into 3V3 pin?