MacBook Pro 15" 2011 not charging after battery replaced

Hi everyone

I've bought MacBook Pro late 2011 on Gumtree and not charging

Things what I know:

- obvious things I've done ie. SMC and PRAM reset.

- got 2 front corners bit bent (nothing cracked)

- genuine Apple charger is green light only and when disconnected MacBook switching itself off (even when battery is connected to motherboard)

- new replaced PowerHut brand battery is detected and showing 100%

- new replaced charging port

- MacBook is going to "Sleep" randomly... when battery is connected to motherboard - when press space key it's waking up.

- no visible evidence of liquid damage

- when battery is connected to motherboard and press 'battery button' green lights flash randomly - which means - sometimes all flash and dim like as fully working - other time just one light appear - other time all flash 3 times

- when battery is disconnected from motherboard everything works as it should (apart no obvious hold on charge)

It looks like battery is doing something wrong - but what? It is new and connector looks ok.

Thank You everyone in advance for help