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power for trailer plug

Started by puravida, May 26, 2007, 01:07 PM

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puravida

With help from this forum I was able to recently install my Tekonsha brake controller.  All I have left to connect is the power from the tv to the trailer plug for charging the pu battery.  Can someone give me some help?  My tv is a 1994 Isuzu Rodeo.  Thanks in advance.

Tim5055

Quote from: puravidaWith help from this forum I was able to recently install my Tekonsha brake controller.  All I have left to connect is the power from the tv to the trailer plug for charging the pu battery.  Can someone give me some help?  My tv is a 1994 Isuzu Rodeo.  Thanks in advance.
Well, this is the one connection that is the same for every make/model vehicle.

You really want a direct connection to the positive terminal of the tow vehicle battery.  Use a sufficiently large wire (#12) and put a fuse/circuit breaker close to the TV battery.

Route the wire in a safe location, away fromboth moving and hot parts.

AustinBoston

Quote from: Tim5055Use a sufficiently large wire (#12) and put a fuse/circuit breaker close to the TV battery.

This is NOT ADEQUATE and can be dangerous.  A short in the charge line will be powered by either battery; if you only fuse one, the other will maintain power to the short, resulting in big problems, including the distinct possibility of a fire.

What is usually done is to use a 12V self-resetting breaker at the camper battery, and a slightly larger fuse at the tow vehicle battery.  

During a simple overload, the breaker will trip, and the fuse will remain intact.  

During a short, first the breaker will trip, then the fuse will blow.  The breaker will keep resetting (after 20-30 seconds), but will trip again (and again and again) before damage occurs.

I have a #10 charge wire with a 30 amp fuse in the TV and a 25 amp breaker at the pop-up battery.  Whatever size wire you use, be sure the ground wire is at least one size larger (smaller numbers are larger wires), because it carries all of the ground current, not just the charge line.

Austin

puravida

Thanks for the update.  The first response seemed a little too simple.  How bad can screw-up my electrical system on the tv if I wire something incorrectly?  In other words should I just pay someone to do it correctly?  I feel comfortable working on my vehicle, but electrical issues make me nervous sometimes.  Thanks again for all the help.

AustinBoston

Quote from: puravidaThanks for the update.  The first response seemed a little too simple.  How bad can screw-up my electrical system on the tv if I wire something incorrectly?  In other words should I just pay someone to do it correctly?  I feel comfortable working on my vehicle, but electrical issues make me nervous sometimes.  Thanks again for all the help.

Electrically, this is about as simple as it gets.  A single wire, connected to the positive terminals of each battery.  On the tow vehicle, the wire needs a 30 amp fuse within a short distance (about 8 inches).  The wire goes to the correct terminal on the plug, and from the same terminal on the camper plug to the positive terminal of the camper battery.  On the camper, the wire needs a 25 amp self-resetting breaker within a short distance (about 8 inches).

The worst that can happen is that you have to keep replacing the fuse.

Austin

tknick

In addition to the fuses and breakers, consider adding a relay to the charge line.  The relay will disconnect your PUP battery from the TV battery when the engine is not running.  If you have a refrigerator running on 12v and you stop for a long lunch, you may come back to find your TV battery is not strong enough to start the car.  

There are 4 terminals on the relay.  IIRC, one terminal is for the line coming from your battery, one terminal goes to your PUP battery, one is a ground and one is a 12v source that is only hot when the engine is running.  You can get the relay from any auto parts store.   The only part that may be difficult is finding the switched 12v source if you aren't comfortable with electricity.

If you don't have a fridge or any 12v drain while stopped, the relay isn't necessary.

travis

wavery

Well....I hate to throw a monkey wrench into the works here buuuuuuuutttttt.......I would not wire directly to the battery (personal preference).

You may find it better and (possibly) easier to run your hot lead from the positive side of your starter. On some vehicles, the stud on the starter sticks out far enough to install a 2nd nut. That way you just put a large eye on the end of your charge wire, slip it on the stud and put an appropriate sized nut on it. You will still want to fuse both ends of the wire (as AB mentioned).

That way, you are not disconnecting anything on the TV and the charge wire is down out of site and exposure.

I never feel comfortable about running a hot wire directly to the battery. Maybe it's just my many years in the marine industry.

AustinBoston

Quote from: waveryYou may find it better and (possibly) easier to run your hot lead from the positive side of your starter.

This is getting messy...did you mean starter SOLENOID?  The starter only has power when you are starting the vehicle.  While many starter solenoids are built into the starter nowdays, that is certanly not true of all tow vehicles on the road today.

QuoteI never feel comfortable about running a hot wire directly to the battery. Maybe it's just my many years in the marine industry.

There are good reasons not to do that.  Some other options are to connect directly to the voltage regulator (not my preference) or to an unused Aux terminal in the fuse block (complete with a spot for a 30 amp fuse).

Austin

wavery

Quote from: AustinBostonThis is getting messy...did you mean starter SOLENOID?  The starter only has power when you are starting the vehicle.  While many starter solenoids are built into the starter nowdays, that is certanly not true of all tow vehicles on the road today.



There are good reasons not to do that.  Some other options are to connect directly to the voltage regulator (not my preference) or to an unused Aux terminal in the fuse block (complete with a spot for a 30 amp fuse).

Austin
AB.....
That's why I said,"You may find it better and (possibly) easier to run your hot lead from the positive side of your starter"

When the battery cable goes directly to the starter (most vehicles), it is hot all the time. The solenoid is what controls the relay that runs the starter motor. The battery cable merely supplies the power. Otherwise, your starter would be running constantly.

By far....the BEST place to hook it is "an unused Aux terminal in the fuse block".

My point was.........it is NOT best to run the wire directly from the battery. :sombraro:

AustinBoston

Quote from: waveryAB.....
That's why I said,"You may find it better and (possibly) easier to run your hot lead from the positive side of your starter"

Ah, but you are assuming people actually think.  Some do (though very few besides you and me always do), but it's not unusual for a thread with only a handful of posts to be read by hundreds of people.  Who are these people?  I often see people logged in (look down the bottom of the front page) who have never posted, not even once...who are they?  How competent?  Do they know how to tell when they "may" or "may not?"

Of course, no matter how clear you are, there are always going to be some who misinterpret.  We can't protect people from their own stupidiy (especially my own), but I try anyway.

Austin