Hi, I'm currently working on a project: I'm trying to make a cell phone charger from an Altoids tin and batteries. I know there are countless tutorials out there, but I want to understand why everything happens and how it works. I'm getting to each problem individually, so that I can find a solution for that specific problem and understand what's going on. I have two 9V batteries I want to connect to a female USB end, then connect a USB charging cable from the phone to the batteries. I'm using an old phone, so I don't mind accidentally screwing it up, I'm just worried about getting the power to the phone initially; and then I'm worried about getting the correct voltage and amps to the phone. Thus far, a single 9V battery connected to the phone via the USB circuit does not cause the phone to respond. Why is this? Also, would any other battery combination be more efficient, and for what reason? Thanks in advance for any attempted assistance.