Late 2013 Macbook Pro takes full days to charge ; battery drops when unplugging charger?

My Macbook pro has to charge overnight to get an even usable charge (usually 50%), and when I unplug the charger from it drops to around 1-6%. I just replaced the battery and coconut app says its fine, charging with enough watts, etc. Have no idea what is going on.

Edit: should note, it only charges when off. When its on it claims its not charging. Unplugging the charger while its on causes it to drop or completely turn off.

Solution 1:

Logically, there are three possibilities:

a) the charger is faulty
b) the power management unit is faulty
c) the battery is faulty

The charger is the easiest to test: see if you can find another Magsafe 2 charger.

Realistically, the other two need to be tested by an Apple Store or other authorised/qualified technician.

Apple don't sell replacement parts to the public, so any battery you bought will be a third-party attempt to match the specification (within costs). Printed text saying "Designed by Apple" etc is unlikely to be a guarantee of anything.