GL-X750 - Spitz - voltage range for a rechargeable battery

Hi, i will buy a battery pack for my GL-X750. In one forum i have read something about the Minimum Voltage (at start 9,6V and when it run 8,2V). But where is the Maximum? Please i need help.

I have found a 11000mAh polymer lithium-ion batterie with 10,8-12,6V and max current 2A. Does this work?

10.8V 2A can make the X750 work properly

And tolerate the board 12,6V? What is the Maximum Voltage?

The maximum voltage is 18V