If you use a NiCd rechargeable battery you may find it completely ... a switching voltage regulator to increase the voltage from 2.3V to 9V. With a light load the cap will last up to 3 hours ...
It’s a project called snapVCC, and it turns a 9 volt battery into a regulated 3.3 or 5 volt supply. The idea behind snapVCC is simple enough; just add a circuit board to the top of a nine volt ...