Your logic board has a problem within the charging control logic. One or more of the MOSFET’s has been damaged. Likely from a bad or fake MagSafe charger.
This is going to take a bit of work to fix and someone who has the proper skills and tools to do it.
Part of the problem is you can’t tell the real from the fake! And may people selling them will claim they are real. The only source I buy chargers is directly from Apple!
* [https://lifehacker.com/dont-replace-your-macbook-charger-with-a-cheap-knockoff-1825605569|Don't Replace Your MacBook Charger With a Cheap Knockoff]
* [https://beetstech.com/blog/oem-magsafe-chargers-vs-counterfeits-teardown-for-truth|OEM MagSafe Chargers vs Cheap Imposters: Teardown for Truth]
* [http://www.righto.com/2016/09/why-you-shouldnt-use-cheap-macbook.html|Lacking safety features, cheap MacBook chargers create big sparks]
* [http://www.righto.com/2016/03/counterfeit-macbook-charger-teardown.html|Counterfeit Macbook charger teardown: convincing outside but dangerous inside]
Apple at one point made a large effort to stop the importation of these fake chargers, but with the intro of the USB-C standard for charging their MacBooks, Apple has stopped fighting. In fact I think they see this as a great way to kill off the older systems forcing you to get a new Mac!