From: Mark J. Blair (ke6myk_mvlist@sbcglobal.net)
Date: Thu Oct 02 2003 - 20:26:17 PDT
I recommend putting a battery switch (which can be keyed if desired), rated
for much more than the alternator capacity at continuous duty and much more
than the cranking current at intermittent duty, in the positive battery
connection. You normally disconnect the ground lead first so that you won't
inadvertently short the battery (either the whole thing or at the 12V tap) by
touching a metal frame/body/battery box component with the wrench. The battery
switch can safely go in the positive lead, since there's no risk of
accidentally shorting the battery out when switching it. It's much easier to
turn off the switch before working on the truck than it is to pull a battery
lug off, so you'll be much less likely to skip that important step before
working on the truck. Plus, it offers a small improvement in security, and
prevents battery drain if you forget to turn something off, or somebody
fiddles with the controls.
I use Pollack brand switches which I ordered from Wire Connections
(http://www.wireconnections.com). They are much heavier switches than the
cheesy knife-switch or plastic keyed switches available at regular auto parts
stores. They are available either with a lever (which is shaped very similarly
to the starter switch on some trucks, such as the HMMWV), or with a key (all
of the keys are the same and they're just simple warded keys made from sheet
metal, so it's not a great theft deterrent, but at least it keeps curious
fingers from turning things on and draining the batteries). The switches are
also available with a separate smaller set of contacts intended for turning
off the alternator field circuit, so that the disconnect switch can be turned
off while the engine is running without damaging the alternator.
In a 2.5-ton multifuel, the switch can be mounted in the floor of the cab at
the right rear corner, right above the battery compartment. Locate it so that
the cables normally attached to the positive battery lug can be relocated to
one of the lugs on the back of the switch. Then, buy or make a new cable to go
from the switch to the positive battery lug. Since the switch can't be reached
from the driver's position, I didn't bother using the kind with the extra
contacts to shut off the alternator. I figure that in the unlikely event that
a passenger flips it off while the truck is running, they can pay for the new
alternator after I finish kicking the fudge out of them for messing with the
controls of a 15,000 pound truck while it's in motion and not under their control.
I like to use the "high flex" battery cable from McMaster-Carr
(http://www.mcmaster.com) to make new battery cables. They carry the cable in
red or black, various ring terminals for it, crimpers (either the relatively
inexpensive hammer-and-anvil type or the expensive bolt-cutter-style ones),
heat shrink tubing (including stuff lined with a layer of hot-melt glue, which
forms a nice seal around cables and lugs), and they even have the
military-style battery lugs. I don't remember what size of cable I generally
use. The cable doesn't have the thick, fiber-reinforced jacket of the original
cables, but it's still heavy-duty stuff, and makes nice replacement cables in
my opinion.
-- Mark J. Blair, NF6X <ke6myk@sbcglobal.net> PGP 2.6.2 public key available from http://www.keyserver.net/ Web page: http://www.qsl.net/ke6myk/
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