I come from Liuzhou. I used Lego when I went to Japan to play the World Cup in 2005.
It rings now.
I don't have specific data, but I have some experience.
Theoretically, the operating voltage of Lego RCX is 9V(6 5th batteries).
But once a big brother connected four batteries to it himself.
Normal test values of the test run program (without connecting output devices, such as motors)
It can run normally! (Plus electrical appliances such as motors have not been tested)
The maximum can be increased to 12V (according to people on the forum).
The above is only personal testing experience.
There are no specific data.
Provide reference!