I would reconsider the pipe - it is RIGID and any
expansion/contraction cam break the posts out of the batteries. Rather
use a few copper ribbons cut from copper flashing and bent to allow
some movement. Broken links inside batteries can cause battery
explsions. Don't ask how I know - suffice it to say I used sheet
copper ribbons to connect the batteries in my electrified Fiat.
The vibration and movement in an 'electrified Fiat' is probably more than
what we're going to experience in any permanent setup.
But for the record, even very large batteries like the ones we used on
submarines can be bolted with 'rigid' connections. The cells are wedged
tightly together with wooden wedges, then the connections made up. We never
had more than about 7 cells connected in a single row, but that was for
magnetic field suppression. The 7 cells would be connected with eight
pieces of lead-covered copper bus bar about 1 foot long. Each cell measured
about 18" square with the negative posts on one side of one cell connected
to the positive posts of the adjacent cell. After about six of seven cells
in one row, the bus-bars would jump sideways to cell in the next row for
about six cells. This formed adjacent loops that would cancel their
magnetic fields (to foil magnetic mines).
Despite all the 'angles and dangles' the boat would take on, we didn't have
a problem with inter-cell connections working loose very much (did test them
while doing test-discharges every month).
daestrom
P.S. For safety, we only used shortened, non-sparking (phosphor-bronze)
tools in the battery well. Including a specially made torque wrench for
making up bus-bar connections.