Acer laptop can no longer be started?

What to do if the laptop (Acer Aspire 7535) no longer starts up and only shows a black screen. But the power button lights up. The power supply is not because I tried several Acer power supplies and once without the battery and only with the power supply. The battery can no longer be charged and before that, when the laptop was still working, the laptop was only running with the power adapter. Do you have to start it emergency? If yes, how or with which key / key combination?

Hold the power button down until it goes out and try again.

If Jensen's answer goes no further, the CMOS battery may have run out.