can i use 4 rechargeable aa batteries for a usb charger?
I found a lot of portable usb charger Instructables using a 9v and a 5v regulator and one that used 2 aa with a 5v boost converter. if I'm using it to charge a device that uses a 3.7v li-ion, then wouldn't any voltage above that work, so as long as it's not high enough to damage whatever it's charging? so would putting 4 aa (4.8v) with just a capacitor and diode work as a safe portable usb charger? or does it need to be exactly 5v?