Can you insert or attach a photo of the control box to help us identify it?
You are correct, that is a Voltage control box which is also known as a DC-DC Voltage converter.
We do not have the PC board schematic for that Voltage converter however we do have new units available which will replace it. They are our item # CVT-7212 and they are available on this page: http://www.electricscooterparts.com/voltage-converters.html
Item # CVT-7212
Please let us know if you have any questions.
Most Wuxi Xufeng XGY electric scooters have 48 Volt battery packs which are made from four 12 Volt 20Ah batteries.
If a single 12 Volt battery was installed that would not damage anything as long as it was installed with the correct polarity to the wiring harness. If a 12 Volt battery was installed with reverse polarity that would damage the DC-DC converter.
Please note that although installing a 12 Volt battery in the correct polarity would not damage anything, the scooter would not run on the 12 Volt battery because the controller needs a 48 Volt battery pack in order to operate.