Power on problem
A few days ago Mac did not start, it remained with the black screen. My friend had the same problem and told me to open the case, disconnect the battery, connect it to the power supply and, then, try to turn it on. The computer turned on. If I reconnect the battery while the Mac is turned on, it continues to work, even if I unplug the power supply, so it works normally, but if I turn off the computer and I try to turn on without the power supply It doesn't work, so I have to repeat the procedure.
MacBook Air 13″, macOS 10.15