motherboard - Laptop stops charging after seconds when plugged in and turned on

I have tried the answers here Laptop battery says plugged in, not charging to no avail.

I have a Lenovo G50-70 running Win 10.

The laptop charges fine when turned off, but when turned on it doesn't charge at all. Taking the charger out and putting it back in - it charges for 30 seconds at most and then stops.

I have tried replacing the charger.

I am now one short of just buying a new laptop - a new battery is about £70 and if it's something internal I can't imagine parts + labour would be cheap.

Here is a screenshot of my BatteryInfoView: https://i.imgur.com/yW3qmDr.png

As an extra point, the battery gets to about 20% and then jumps to 7% - I know this is due to it obviously need re calibrating but I am wondering if it is part of the reason.

Thanks