Isolator Wiring
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Isolator Wiring
I have an 03 Expeditioni XLT with Factory towing package. I tow a 20' Enclosed Car hauler with it (for a race car). I want to install a 2nd battery in the trailer for the winch and some lights. I would like to be able to charge the battery while in route from the truck. I understand that a battery isolator may be needed so I don't drain the Expedition's battery while at the race track. Problem, I am not the only person who uses this trailer.
Is there a way to install an isolator IN the trailer and no on the truck so it is available to anyone towing the trailer? (IE I don't need to make any modifications to the tow vehicles, just the trailer) Is there someone else I should be using other than an isolator?
From what I gather the center pin on the 7-way connector is a charging/wiring 30Amp circuit. Isolators have 3 post. Center post is alternator two on sides are for the batterys.
Thanks for your help,
--chad
Is there a way to install an isolator IN the trailer and no on the truck so it is available to anyone towing the trailer? (IE I don't need to make any modifications to the tow vehicles, just the trailer) Is there someone else I should be using other than an isolator?
From what I gather the center pin on the 7-way connector is a charging/wiring 30Amp circuit. Isolators have 3 post. Center post is alternator two on sides are for the batterys.
Thanks for your help,
--chad
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From: Virginia
The isolator on the trailer won't work because the alternator would not charge the truck battery unless the trailer was plugged in. It would be an awful long way for the charge circuit to go too.
I think the simplest solution might be to use the 30 amp charge circuit as-is. Then when you get to the race track, unplug the trailer.
I don't have my diagrams with me, but you may find the charge circuit on your truck has a relay that is triggered by the keyswitch in the truck. If that is the case, you have nothing to worry about anyway. If you do not have the relay, and the 30 amp circuit stays hot all the time, you could add a relay to cut it off when the truck is off. With a relay, it would seperate the trailer battery from the truck's battery automatically when the key is off.
I think the simplest solution might be to use the 30 amp charge circuit as-is. Then when you get to the race track, unplug the trailer.
I don't have my diagrams with me, but you may find the charge circuit on your truck has a relay that is triggered by the keyswitch in the truck. If that is the case, you have nothing to worry about anyway. If you do not have the relay, and the 30 amp circuit stays hot all the time, you could add a relay to cut it off when the truck is off. With a relay, it would seperate the trailer battery from the truck's battery automatically when the key is off.
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Thanks for the input guys.
So all this stuff I'm reading about causing damage to the truck battery is bogus?
I'm reading that, say I drain the trailer battery down to 7 volts, then hook backup to go home, the two batterys are now connected in series together with the truck battery having 13-14 volts. Since the two batterys will try to equalize it will cause damage to the main battery. Is that a real concern?
Another question. What would be the problem with putting the isolator in the trailer, running the 30amp wire you are taking about to the center post of the isolator and only hooking up 1 battery (the one in the trailer) to the other post on the isolator. That would prevent the trailer battery from draining back into the truck battery and lowering its voltage right? Once the trailer battery reached full charge it would no longer draw current off the alternator and truck battery. Or is that overthinking the situation or not a proper use of the isolator?
Thanks for the help.
--chad
So all this stuff I'm reading about causing damage to the truck battery is bogus?
I'm reading that, say I drain the trailer battery down to 7 volts, then hook backup to go home, the two batterys are now connected in series together with the truck battery having 13-14 volts. Since the two batterys will try to equalize it will cause damage to the main battery. Is that a real concern?
Another question. What would be the problem with putting the isolator in the trailer, running the 30amp wire you are taking about to the center post of the isolator and only hooking up 1 battery (the one in the trailer) to the other post on the isolator. That would prevent the trailer battery from draining back into the truck battery and lowering its voltage right? Once the trailer battery reached full charge it would no longer draw current off the alternator and truck battery. Or is that overthinking the situation or not a proper use of the isolator?
Thanks for the help.
--chad
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From: brooks a.b.
there is no damage occuring to the truck battery while driving down the raod. remember that the alt is charging the batteries not one battery to another. you can shorten the life of the truck battery if you where to drain it dead then recharge it many times. that is why the trailer battery should be a deep cycle battery. one thing to mention is to be sure to fuse the charge line to trailer. one draw back to a isolator is that there is a voltage drop as the power passes through the diodes. so instead of 14v to the trailer battery you get 13v, it may not sound like much but the battery will sure act differently with that less of a charge. also remember that a battery always takes a little bit of charge when the alt is charging.
Last edited by cheez67; Mar 21, 2006 at 07:49 PM.
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From: Virginia
The batteries will try to equalize each other when the trailer is hooked up. In some cases this would be a concern, and cause battery damage. In your case you have a long distance between the two batteries with a smaller guage wire, and it is also fused with a 30 amp fuse. So the worse case senario is you will blow the fuse. 30 amps will not damage either one of the batteries.
So I would try it. The worse that could happen is you get nuisance fuse blowing. If that becomes a problem, I think I would go to the parts store and buy a circuit breaker. They have them that self reset. It may be possible you could put a little bit larger fuse in, and then buy a 30 amp circuit breaker. Or possibly buy a 20 amp circuit breaker. The circuit breaker would cut on and off till the trailer battery built up enough for it to stay on all the time. This is the way the small home battery chargers work.
People with multiple batteries using large high amperage wire connecting them over short distances are the ones that need to worry about battery melt down.
So I would try it. The worse that could happen is you get nuisance fuse blowing. If that becomes a problem, I think I would go to the parts store and buy a circuit breaker. They have them that self reset. It may be possible you could put a little bit larger fuse in, and then buy a 30 amp circuit breaker. Or possibly buy a 20 amp circuit breaker. The circuit breaker would cut on and off till the trailer battery built up enough for it to stay on all the time. This is the way the small home battery chargers work.
People with multiple batteries using large high amperage wire connecting them over short distances are the ones that need to worry about battery melt down.
< Samantha...my Co-Pilot
Joined: Dec 2001
Posts: 768
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From: Fallon, Nevada
Hey Guys, I don't mean to hijack this post, but I have a question along the lines of this post. Like white_2kgt, I have an enclosed car trailer and want to be able to operate the interior lights when the trailer is not plugged into my truck. If I added a deep cycle battery and fused the positive post to the auxiliary 30 amp lead( yellow wire/center pin on seven pin wiring plug) and connected the negative post to the trailer ground/wiring plug ground, would this be all that is necessary? If my thinking is correct, this will allow the battery to charge while towing the trailer and operate the lights while not plugged in to a tow vehicle.
Last edited by Jakebrake; Mar 22, 2006 at 12:15 AM.
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From: Utah County, UT
Originally Posted by Jakebrake
Hey Guys, I don't mean to hijack this post, but I have a question along the lines of this post. Like white_2kgt, I have an enclosed car trailer and want to be able to operate the interior lights when the trailer is not plugged into my truck. If I added a deep cycle battery and fused the positive post to the auxiliary 30 amp lead( yellow wire/center pin on seven pin wiring plug) and connected the negative post to the trailer ground/wiring plug ground, would this be all that is necessary? If my thinking is correct, this will allow the battery to charge while towing the trailer and operate the lights while not plugged in to a tow vehicle.
http://www.rverscorner.com/wiring/four.htm
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< Samantha...my Co-Pilot
Joined: Dec 2001
Posts: 768
Likes: 11
From: Fallon, Nevada
Thanks for the reply. I think I will do it your way and use the +12 volt pin 4 instead of the auxilliary power pin. I just need to come up with a battery tray to mount on the tongue of the trailer.
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