Lets go through the basics:
Review this Apple T/N [https://support.apple.com/en-us/HT203207|Apple Portables: Troubleshooting MagSafe adapters] Make sure the MagSafe cord is not damaged. If it is you’ll need a new charger. Also make sure the systems contacts are clean and gold colored, not black!
Make sure you have a real Apple charger, there are a lot of fake units which can harm your system and you! [https://beetstech.com/blog/oem-magsafe-chargers-vs-counterfeits-teardown-for-truth|OEM MagSafe Chargers vs Cheap Imposters: Teardown for Truth] This is why the contacts can be black [http://www.righto.com/2016/09/why-you-shouldnt-use-cheap-macbook.html|Lacking safety features, cheap MacBook chargers create big sparks]
The last step is to monitor your battery and charger using this gem of an app [https://www.coconut-flavour.com/coconutbattery/|CoconutBattery] Take a snapshot of the apps main window and post it here for us to see [[guide|21499]|