I brought 0.9V-5V to 5V DC-DC Booster Module from eBay and I thought you should know the fact about this module before you buy it.
The circuit module is very cheap (2 pcs for 1$ from eBay with free shipping) and very tiny to fit the small projects that require batteries if you not serious about Voltage swing with low voltages than 2.4 volts source.
You can see the test video below.
The advantage of this step up module:
- high efficiency
- incredibly low cost
- small size
Enjoy your project!!!