--- In alinerchaleta-frames@y..., "pre64winchester" <bbaile@s...>
I am guessing I would start with a piece of number 8 stranded wire
at
the vehicle battery, and run it to my vehicle plug. I would also
want
to run that wire in a plastic jacket to protect it since it would
have to be run under the vehicle.
Question #1. What size fuze would I use. I think I would want this
near or at the vehicle battery?
#8 is good for 50 Amps but a more realistic fuse would be a 30 Amp
dual blade automotive fuse in a water tight holder. These are
available from any automotive store and are relatively small.
Question #2. Where would you install the battery isolater, under the
hood, or in the trailer? I hear of too many vehicle
batteries going dead with out an isolater.
To install anything under the hood of the Explorer would be like
adding another sardine to a full can.
A diode type isolator contains two large diodes (electrical one way
valves), one to feed alternator current to the vehicle battery and the
other to feed alternator current to the trailer battery. Since it has
to be installed between the alternator and the Explorer's battery, it
has to be under the hood. Diodes are not lossless devices; they
typically have up to 1 volt drop at high current resulting in heat
generation of about 1 Watt per Amp so the isolator housing can get
quite hot and is fairly large to dissapate the heat into the
surrounding air. I haven't an Explorer to examine but you may have
your work cut out for you trying to fit an isolator in there.
Another approach is to install a relay (electrically remotely operated
switch) between the alternator and the wire to the trailer battery,
operated by either the ignition switch or a separate switch inside the
car, so that it only connects the trailer when the engine is running.
The relay would be much smaller than a diode type isolator, much less
heat (only a couple of Watts for the coil), and almost no voltage
loss. The relay COULD be installed anywhere in the wire to the trailer
but, since it also needs a wire to tell it when to turn on, it is best
installed somewhere in the engine compartment. Altogether a smaller
and simpler installation.
One problem with charging a trailer battery from the car is that
lead-acid battery chemistry is temperature sensitive, requiring about
1 volt less charging voltage at 125F than at 70F. Most automotive
voltage regulators sense the underhood temperature and reduce the
alternator voltage as the engine compartment warms up to avoid
overcharging and damaging the car battery. The reduced voltage from
the alternator, added to the voltage lost in the resistance of the
wire from the alternator to the trailer battery (larger wire is
better!), results in the cooler trailer battery not being recharged to
the extent one might hope.
-Jay
