LENOVO ThinkPad T420s Series computer batteries, Laptop Battery - YouTube
Status indicators - ThinkPad T420, T420i
Amazon.com: Lenovo Thinkpad T420 - Intel Core i5 2520M 8GB 320GB Windows 10 Professional (Renewed) : Electronics
Lenovo ThinkPad T420/T420i - iFixit
T480 charging issue. Red light is showing but laptop is not charging. Sometimes it gets opened and gives error message- "The connected AC adapter has a lower wattage than the recommended model
Lenovo Thinkpad T420s review
Lenovo ThinkPad T420s Power Jack Replacement - iFixit Repair Guide