Put all three batteries in parrallel - i.e. connect a wire from the positive
terminal of the first battery to the positive terminal of the second
battery, and then to the positive terminal of the third. Do the same with
the negative terminals. With a multi meter you should see about 12-14
volts - if it is any more then you have not connected the batteries
correctly.
To ensure that the batteries remain charged, connect a charger to the
batteries (only one needed as the wiring above will ensure that the other
two batteries are also charged up) - unless you are using the batteries, you
will only need a relatively low current trickle charger to ensure that they
are all kept topped up.
I have a number of smaller gelcell batteries (between 7 and 24 AH in size)
that I use in a similar fashion. Works well for me. One additional thing,
I also have a small solar panel (about 35W) that I can also use when there
is no mains power to recharge the batteries (and you don't want to waste
fuel running the car). You can also get some small generators (around the
850W size) for very cheap prices (have seen them for as low as $50) - not a
bad idea for provision of emergency power, and can also be used to recharge
your batteries. However, your three batteries should well and truly last
for the time that it takes to get mains power back up and running, but it
always pays to be prepared.
My power distribution consists of a small homemade power bar connected to
the batteries. It is a plastic box with two strips running the length of the
box which are connected by wires to the batteries. From the metal strips I
have a number of terminals that the power cables from the radio gear are
plugged into. Hard to explain it without piccies, but no can do as almost
all my gear is in storage while I am in the process of moving house!
Bit of a rambling dissertation, but hopefully you understand it - if not,
query away.



Matt

"DX99" wrote in message
news:Ocane.16813$tv3.6440@trnddc06...
Getting ready for the upcoming hurricane season here in FL and wanting to
develop an affordable power backup for my radio desk in the inevitable
event
of a power outtage. I have 3 brand new 12-volt automotive batteries -
unused - in my garage. How would I go about wiring to power 4 scanners and
a
shortwave? All suggestions/directions appreciated.

K