How I can make alternative method for keyboard charger by without lid.

when i need to charge keyboard battery.

SONY tap 11 is design method by close the keyboard and tablet together.

like this

but sometime i need to use keyboard for longtime. until battery gone. this method is not work for me.

i want to find some idea for make a cable port to connect it.

If i can connect it by three wire.

Will the computer is work and keyboard still charging?

or

If i have to know the voltage all of 3 pin and i can connect it with converted voltage battery.

can i make a standalone keyboard charger?