Power source for arduino project
I've been using usb power packs.


Easy to source (can be found in all electronics stores and many general stores).
Come in many sizes (500mAh to 20,000 mAh are common).
Rechargable, usually by using a generic phone changer with a usb micro connector.
Not costly.
Quite roubust.
Most Arduino boards and many motor driver boards are designed to be powered from usb.


Make sure you get one that is rated for enough current for your project.