I’ve got the Ace, not seen any charging issues with it - I use a 100W PD certified charger and it’s been fine.

Is the 15W charger you mention its actual power-output?

Is it PD certified and USB-C to USB-C?

Have you tried a ‘power reset’ of the Ace (not a factory reset)? 

I have no idea but it says on the label 15W PD Power adapter so I guess it is and yes its USB-C to USB-C.

When I plug it into my headphones the light turns blue and it connects to my phone.. havnt tried a ’power reset’ how do I do it? :)

When you plug the Ace into the charger - its status LED should turn Amber, not Blue? It should not be able to connect to anything whilst it’s charging from a power adapter. 

Try this - with the Ace powered ‘off’…press and hold its power button for about 10-15 seconds. It will power ‘on’ - keep the power button pressed (do not let go) and it will go into pairing mode (flashing blue LED), but keep it pressed and you may hear it click (LED stops flashing) and it should power-reset. 

Now power off the Ace and then plug it into the charger and see if you get an Amber status LED - if not then maybe try a different charger.

Can you perhaps also post a screenshot here of the power output ‘label’ on the charger you’re using.

Tried it now but no ’Amber light’ appeared,no light at all actually not until I moved the cable abit then it turned blue again… no luck. 

Anyways thanks for the help I guess I will have to keep track on the battery life so it doesnt run out of battery and then keep ’factory reset’ the headphones to charge them full again..

This 100W charger, just as an example, has two USB-C ports that can output at various voltages in compliance with the PD standard - I have highlighted that one, or both, of its ports can output 5V x 3A which is 15W - see image below. So both of its ports will charge the Ace or even two Ace headphones simultaneously. So that’s the type of thing you need to look for on your charger…

I don’t think that charger will work too well, it’s 5v output is only 2A = 10W. I suspect that’s where  your problem may lie - try to borrow and test with a charger that shows 5V x 3A power output and see if that will sort your issue.