I do apologise but I thought I was already assuming the power i/p would be the same as is used with the proper ac transformer. I am trying to connect a 12v supply directly to the power i/p with the battery out so I am not connecting to the battery terminals. Or I am again missing something? Perhaps ...

Thanks for the prompt reply. Can you enlighten me as to why the t23 will only operate at 16v and with the battery in place?
Sorry but not the solution I was hoping.

Can someone tell me if there is a modification I can do to run my t23 directly from a 12v battery. Other laptops can operate this way with the battery removed but the t23 thinks that all power is disconnected when the battery is removed. Yes I can use an inverter but I would prefer to use direct 12v...