batteries - Is soldering wires directly on a NiMh battery safe? - Electrical Engineering Stack Exchange
How to quickly solder 18650 Li-Ion Batteries with a soldering iron - YouTube
Soldering Batteries - Robot Room
Amazon.com: GeekLJT New FM Radio Soldering Kit, Solder Project Kit, Portable Radio DIY Electronic Kits Powered by Batteries or USB Cable, Practice Soldering Kit for Learning and Teaching Solder and Electronic :