Cut three lengths of sufficiently thick red multistranded wire. Solder ends of these wires to the bridge rectifier, pins ``+'', ``AC'' and ``AC'' (e.g. the two ``AC'' pins are identical). See Fig 2(a).
Figure 2: Combining the output of two batteries of possibly different types. (a) Solder three red wires to all but the ``-'' pin. (b) Wrap pins and wire in fiberglass tape and epoxy to protect and insulate them. Note that the fourth pin, with no wire connected, is still insulated.
Break off or insulate the fourth pin (``-'').
Connect a red male banana connector (plug) to each of the wires going to the ``AC'' terminals, and connect a red female banana connector (socket) to the wire going to the ``+'' terminal. In this way the power bridge will be modular (e.g. easy to take out or insert at will, depending on usage requirements).