But I'm not sure if you can just connect that to any of the battery pins... battery is 3.7V and individual banks are much less, more like 1.5V each. I'm no expert in this, but I think battery is being charged by applying that small voltage of 1.5V to each battery bank individually.
My RC heli Li-Poly battery had 3 banks and charger was charging each bank independently, I could see 3 separate voltages.
So I wouldn't try connecting 5V charger to battery directly, it might explode.
---------- Post added at 09:14 PM ---------- Previous post was at 09:02 PM ----------
Hey, it might be better idea to get that cheap USB external charger for any phone (I think if it has the same count of pins as the battery we can assume it would work, as most phones come with similar 3.7V battery) and use cables to connect charger pins with battery pins, in the same order.