I'd use a prototype breadboard and use a diagram like the one attached. Solder the resistors and the USB cable to the breadboard on one end and attache something like alligator clip wires to the opposite end. That way you can use it for all different batteries. Any iPod/iPhone charger AC charger in theory would work, all you have to do is find the pinout i.e. pinout.ru and tap it from a USB cord. Then connect your battery via alligator clips to the circuit.
This would be a circuit to use from a 12volt charger. There are so many variations out there give it a try and see what will work for you. Of course make sure that you have a multimeter and measure your circuit before you try to charge your battery. there is great infromation on here and here. Hope this clarifies it a bit....:-)