Charge battery while towing on 7-way plug - Fiberglass RV
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Old 10-15-2017, 06:52 PM   #1
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Name: Jeroen
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Charge battery while towing on 7-way plug

I've bought a 7-way plug for the Scamp I'm rebuilding. Can I hook up the auxiliary power (black and white) directly to the battery?
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Old 10-15-2017, 06:55 PM   #2
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Originally Posted by jeroen View Post
I've bought a 7-way plug for the Scamp I'm rebuilding. Can I hook up the auxiliary power (black and white) directly to the battery?
I'm just learning about this stuff myself, but I believe the black wire has to be fused.

Not sure if this link works, but if it does, click download to see the wire diagram:
http://www.fiberglassrv.com/forums/d...?do=file&id=75
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Old 10-16-2017, 04:57 AM   #3
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Can anyway check what size fuses Scamp uses? I'm guessing 40amp. Is there no diode in there as well?
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Old 10-16-2017, 05:17 AM   #4
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fuses

no more than 20 amp

bob
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Old 10-16-2017, 05:59 AM   #5
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no more than 20 amp

bob
This is true, mine is a 20 amp.
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Old 10-16-2017, 06:30 AM   #6
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Quote:
Originally Posted by jeroen View Post
I've bought a 7-way plug for the Scamp I'm rebuilding. Can I hook up the auxiliary power (black and white) directly to the battery?
Quote:
Originally Posted by jeroen View Post
Can anyway check what size fuses Scamp uses? I'm guessing 40amp. Is there no diode in there as well?
What fuses are you asking about? Typically its 20 amp at the trailer battery for the trailer's wiring but I think you are asking about the fuse on the charge line AT THE TOW VEHICLE battery. And that depends on what gauge wire you are using and how it it wired (direct to trailer battery or using part of the trailer's wiring). Fuse should be a value that will protect the entire circuit.

Diode? No.. but a ignition controlled relay or battery isolator is recommended to avoid accidentally killing the tow veh battery if the trailer is hooked up too long and taking too much power.

Plenty of info on this topic online if not in this thread.
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Old 10-16-2017, 09:51 AM   #7
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If you have electric brakes on the trailer you need to have the negative from the brakes connected to the TV through the umbilical negative for best and safest results. That negative path can be connected to the trailer frame ground lug or negative buss or the battery. The trailer battery negative is connected somehow to the trailer 12v circuits and that might be through a frame ground or a bunch of negative wires going to a ground buss. The frame or the ground buss can be connected to the umbilical negative to bond the charging circuit from the TV to the trailer 12v negative. That takes care of the trailer and charging and brake negative side. If you don't have brakes, the 12v negative can connect at the location that all of the trailer 12v negative wires connect which could be the frame or the buss bar. Then a 12v positive charging wire, from the TV umbilical, can go directly to the battery. It's in-line fuse has to protect the smallest wire in the charging circuit. That wire size will be either in the TV charging circuit at the seven pin plug or the trailer charging wire to the battery. Probably one of those two will be a #12 and a 20 amp fuse will be fine. #14 would be 15 amp and #10 would be a 30 amp fuse maximum.

The TV charging amperage is determined by the TV manufacturer so the easiest way to protect that circuit is to match the fuse to the wire size.

Some tow vehicles disconnect the charging circuit with the key off and some don't. If your charging pin at the plug is always hot, you will have to be careful not to run the TV battery down while camped. This can be protected with a solenoid or by unplugging the umbilical while camped.

If you don't have a seven pin plug, it's probably best to convert to one so you'll have a dedicated ground and a 12v positive charging wire, in addition to the light wires. All of this would be connected easily with the one plug.

When you are done, disconnect the trailer from shore power and read the trailer battery voltage after a short battery rest. It should be at about 12.6. Connect the umbilical to the TV but don't hitch the trailer up to the ball. Start the TV and read the trailer battery voltage. It should climb up to about 14 volts. This will prove your circuit is correct for charging.

Then when you arrive at the campsite your battery will be fully charged. And if the charging circuit has enough power, you could run your fridge on 12v while driving.
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Old 10-16-2017, 10:28 AM   #8
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My truck is factory wired with a 7-way connector, so I don't have to worry about the truck-side.

Is this diagram correct for the camper-side?
Attached Thumbnails
wiring.png  
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Old 10-16-2017, 11:00 AM   #9
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Originally Posted by jeroen View Post
I've bought a 7-way plug for the Scamp I'm rebuilding. Can I hook up the auxiliary power (black and white) directly to the battery?
When you bought the 7 way plug you should have gotten a diagram that tells you where each wire goes for lights, battery, etc. If it did not come with the plug then go to an RV dealer and they can give you one. Unless someone did not wire your truck correctly it should match all the items in the diagram. The plug has numbers on it when you take it apart. Each spot is numbered and that tells you where to put each wire. All trailers and TV use the same diagram unless someone has messed with the wiring. No do not wire directly to your battery. If you get a short in your trailer it will take out the truck wiring and if in your truck it will take out your trailer wiring. Been there done that with a camper and truck that was not done properly. Go through an isolator and a fuse. Then you can't run down your TV battery either. We wired our van completely with the diagram coming from the battery to isolator, fuse, lights, etc and it worked perfectly.
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Old 10-16-2017, 11:47 AM   #10
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Might want to check out this video.

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Old 10-16-2017, 12:09 PM   #11
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I would think that on a new truck with a factory towing package and 7-way connector, they would have installed a 20 dollar solenoid in the wiring already. Or not? I guess I'll try to find my multimeter and see if there's any power on that wire if the truck is not running.
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Old 10-16-2017, 02:02 PM   #12
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I would think that on a new truck with a factory towing package and 7-way connector, they would have installed a 20 dollar solenoid in the wiring already. Or not? I guess I'll try to find my multimeter and see if there's any power on that wire if the truck is not running.
My 2014 Ram has a continuous hot at the trailer plug. However, the computer will turn off any loads either after time or pre-determined battery voltage. I think it will turn off the trailer charging circuit too. I would definitely test the system before assuming and installing a solenoid.
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Old 10-16-2017, 02:58 PM   #13
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2013 F150 powers trailer charge line only when the engine is running.
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Old 10-16-2017, 04:17 PM   #14
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My Dodge Dakota powers the charge line full time. Maybe the computer will shut it down, I've never had that happen.
My Chevy Blazer previous tow vehicle had a solenoid installed, which is just another item to fail. I know from experience.
When towing and I stop for a meal I leave it plugged in. If I stop for the night I unplug the tow from the trailer. Still probably wouldn't be a problem. The only time I can it becoming a problem leaving the trailer and the tow connected is when you're camped for more 1 night even two nights in warm weather might be ok.
BOTTOM LINE... Save your money and don't install a solenoid.
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Old 10-18-2017, 06:45 AM   #15
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Right off, I'm not a 12v expert. That said, as it happens, yesterday, I helped a friend install a 7 pin plug on his Nissan truck for his Scamp 5th wheel.

He had ordered the kit from etrailer.com. (great site).

The schematic shows black and white going directly from the battery to the 7 pin plug. NOTE: the black wire has a 40 amp circuit breaker in line.



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Old 10-18-2017, 07:53 AM   #16
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KB- chalk up another one for "etrailer.com". I too ordered the "kit" - wiring, 7-pin socket, breakers, etc for my '99 Nissan 4-cyl. It has the continuous "hot" wire at the plug as Byron describes.

Ok...I DO do the "unthinkable"- I use my Dometic 2193 (3-way) fridge on 12v when I'm on the road. I do not and WILL not run propane. This could possibly start a firestorm but I'm a "veteran".... I dont run an over-sized alternator OR battery. I believe my Scamp has the group (edited) 24- still factory stock from 2010 when the trailer was bought new .

In my nearly 8 yrs, I'm STILL running that same setup. I've even stopped to eat breakfast before and never turn off the fridge nor unplug the Scamp from my truck. Narry a problem- again- in nearly 8 yrs.

Just make SURE you run the heavy-gauged wire (10 ga if it's from etrailer) and it will supply the amps you need to do this. Cant speak for the larger fridges but I think many struggle on 12v. I guess I'm one of the lucky ones.

Quote:
Originally Posted by kingbiscuit View Post
Right off, I'm not a 12v expert. That said, as it happens, yesterday, I helped a friend install a 7 pin plug on his Nissan truck for his Scamp 5th wheel.

He had ordered the kit from etrailer.com. (great site).

The schematic shows black and white going directly from the battery to the 7 pin plug. NOTE: the black wire has a 40 amp circuit breaker in line.



Sent from my Nexus 5 using Fiberglass RV mobile app
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Old 10-18-2017, 08:26 AM   #17
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darrell

Darrell what battery are you running in your tug? my edge will run down the battery looking at it!

I hate that car by the way!

tell us more


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Old 10-18-2017, 08:28 AM   #18
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Do you mean what brand? If so, it's a "Northern" brand which has nothing to do with it in my opinion.

I'm not a "boondocker" so I dont initiate heavy "draws" on this battery. But I HAVE ran it down a couple of times forgetting to turn off my fridge on 12v when arriving back at the house. I finally put a red light inside so when we're unloading, if that light is on, it's on 12V!!! Havent ran it down since.

One secret here- I DO keep a "Battery Tender" on all my vehicles that are not driven often including my Scamp's deep-cycle battery. It's a "Smart charger" and will not hurt the battery. Some will recommend the "Battery Wizard" that comes with Scamps and other FG RV's for their Progressive Dynamics converter. BUT, with this setup, I dont have to leave my Scamp plugged in at all. And no, I dont have a switch to throw to disconnect power into the Scamp. I spoke with PD and they said an external charging source would not hurt their converter. I've been with the Battery Tenders/Minders now about 3 yrs.

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Darrell what battery are you running in your tug? my edge will run down the battery looking at it!

I hate that car by the way!

tell us more


bob
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Old 10-18-2017, 08:46 AM   #19
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darrell t

norther brand car or battery what amperage? big dude small one? great idea on the light where did you place it?

I am being serious here. I want to know your tricks? I am a boondocker no I don't run a fridge on a battery while overnighting I light the fried on gas! but I am terrified about running my battery down!

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Old 10-18-2017, 08:47 AM   #20
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Darrell I don't trust those chargers in the rv good way to burn your battery up. I usually put a battery charger on for a bit before taking off easier on my alternator I think maybe just me!


good ideas


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