Power on

[MNMO]

My zbook fury G6 17” power socket light blinks fast 11 times after connecting it and opening the lid, then stops and all the keyboard lights then illuminate briefly and go out and no sounds occur, display remains blank then the the power socket led lights blink again 11 times and it goes through the same sequence many times all without starting up. Leaving the display closed and the power lead contacted results in the laptop getting warm. If I open the lid the same thing happens. I have removed the battery and drained all residual power by pressing the power on button for a minute and when I reconnect the battery press the power on button the above cycle starts again and it doesn’t power up. The last time I turned it on before all the above mentioned activity was after the laptop had been unused and unconnected to a mains power supply for several weeks. I connected the mains adapter lead, turned it on and the screen displayed a message “installing system updates” so I left it to carry on. When I returned, the screen was blank and the laptop was doing what I have described at the outset. What can I do? I have tested the mains adapter with a digital multimeter and it is showing 19.5 ish volts dc and I know it’s the correct adapter. Is there any way of checking the laptop battery when it’s removed from the laptop? Will replacing it be of any use?