Battery Charger Circuit - Make a 12V Battery Charger at Home
Simple USB battery charger circuit
Simple 3.7 volt battery charger with auto cut off - YouTube
Amazon.com: SYLVANIA - Smart Charger - Heavy-Duty, Portable Car Battery Charger - Make Charging Your Car Battery Easy - Use as Battery Maintainer & Charger - 6V or 12V Voltage Output - 1 AMP : Automotive