I want to use the Li-ion battery pack from an old cell phone that I have for my airplane, but it only is a 3.6 volt pack. Is there a way to increase the voltage? I know that the current would have to be sacrificed in order to do this, but can this safely be done and how would I go about doing it?

PS - I am only willing to spend a little bit of money if any at all.

Thank you

While there are ways to do this it would likly not provide the current you need even for the smallest motors.. You might be able to take 2 of those same batteries and put them together to make 7.2 but again i would not count on the cell phone battery lasting long in this application.

to further what paulvi said, most li ion cells do not provide the current needed for most flight applications. (again, most, yes there are people flying with micro stuff...) they may work a couple of times, but it is way outside their useable limit and will have a very short life cycle, if they do work. also, many liion cells have an internal safety circuit that limits current. it is very likely you would just trip that as soon as you spun up your motor.