I have a 12v air pump, on manual it says current is 9A. So I bought this 240ac to 12v dc transformer it has: 12V 150W 12.5A so I thought the transformer can provide enough current. This is the transformer I bought: https://www.ebay.com.au/itm/DC-12V-24V-Waterproof-Power-Supply-Transformer-Adapter-LED-Driver-36-250W-/371937953390
But when I plug the air pump to the output of the transformer, the voltage dropps to 3.6V which the air pump couldn't keep working. This is a video I took: https://obanau-my.sharepoint.com/:v:/g/personal/todd_liang_obansolutions_com_au/EVljWVMZoytGje_Y-86fKGYBdMTBr3bKtOFa4yBB9FQ9GA?e=YPqaZK
The air pump is working perfectly fine if I use a 12v battery so it has to be the transformer issue, so what could be the reason? Why the voltage dropped so much?
Update2 I also bought a 120W transformer from the same seller and oddly enough the 120W transformer is working perfectly fine, only this 150W (which suppose to be more powerful) doesn't work. I reported this issue to the ebay seller and they sent me a replacement. Today I received the new transformer but it has the same issue.