I'm sorry to offend you, it's really difficult to communicate with you.
I had reply you by email that 3.6V & 18V extra battery can not put in the case because it's no more space to put it.
We only can put 3.6V battery cell in 3.6V case, 12V battery in 12V case, 18V battery in 18V case.
But you ordered this time is one 3.6V item ( Case have no space to put a extra 3.6V battery cell ), two 12V item ( can put 2nd battery in the case of AMB12VT), no 18V item.
Clear now ?