My MacBook Air runs without battery, but not with it.

Hi guys,

I've a problem with my Macbook Air mid 2011 A1369. The Macbook doesn't power on if the (internal) battery is connected. When I disconnect the internal battery and I power on my Macbook via AC-power it boots like a charm.

Since my Macbook is 5 years old, I could imagine I need to replace the battery. So I ordered a new battery and installed it. Unfortunately the problem still exists with the new battery. What could be the problem with my Macbook?

Kind regards,

Sonic1986