I am disabled, dont know a thing about connecting batteries.
Its very simple actually. What you are doing is connecting the DC sources (batteries) in series. The VDC is additive so you end up with ten X 9 V = 90 VDC.
Very nice work!
It made me think of the "gold coin" sebs. We could make our own by having a gold coin installed by CRK and then anodizing with Maple Leaves or Stars and Stripes etc.