Charging from the tow vehicle?

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Charging from the tow vehicle?

Postby Duane King » Wed Jul 25, 2007 12:31 am

How simple is it to get my tow vehicle to charge my teardrop battery while traveling? What kind of wiring do I need for that? Do I run a risk of draining the battery in my tow vehicle?
Duane King

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Postby madjack » Wed Jul 25, 2007 1:11 am

Duanne, it is as simple as running a 10ga wire from the + side of the vehicle battery to the + side of the tear battery(with appropriate grounding)...or as difficult as you wanna makeit...and yes, it will drain the T/V battery...this can be taken care of by 1) simply disconnecting the charge wire, whenever you stop and use the 12vdc power in the trailer...2) getting a fairly inexpensive solenoid, to put in the line(activated when key is turned on...get one rated for continous duty) or 3) get a very (relatively) expensive isolator and wire it into the system......
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Postby steve wolverton » Wed Jul 25, 2007 1:18 am

Aren't there 7 pole plug kits that do this? I've only messed with the flat 4-way plugs.

Hmm. Would something like this work:

http://www.etrailer.com/mm5/merchant.mvc?Screen=PROD&Store_Code=E&Product_Code=30637&Category_Code=
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Postby Duane King » Wed Jul 25, 2007 1:27 am

I actually have a seven pin connector on my tow vehicle even though I've only ever used 4 wires. Because I am down to the wire (literally) on this build and need to be done on Thursday, I am paying a trailer company to finish the wiring in my tow vehicle. They are going to be installing a controller for my trailer brakes. The trailer is fully wired and they don't need to mess with it. They just have to run the brake wire down the length of my vehicle to the receptical in the back. Since they are going to be running this wire anyway, I'm going to get them to run the charge wire from the battery. That is the reason for this post. I want to be sure I get them to do the right thing. The trailer guy says he wants to run 14 guage wire because that is all they have ever used. I said that is too small for a charging line and he said he could do 12 guage. Do I really need 10? If so, I'll get him to do that.

He is also going to run a ground wire through this connector. I assume he can just ground to the frame at the back of the tow vehicle. He doesn't need to run that up to my tow battery. Right?

I'm going to the DMV on Thursday afternoon. I need to be sure this is done right the first time because I won't have time to redo it.

Thanks
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Postby Joseph » Wed Jul 25, 2007 1:35 am

madjack wrote:Duanne, it is as simple as running a 10ga wire from the + side of the vehicle battery to the + side of the tear battery(with appropriate grounding)...

Don't forget the 30 amp fuse.

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Postby Kankujoe » Wed Jul 25, 2007 1:45 am

You may also want to get a "7 pin tester plug." A salesman at the local trailer & hitch shop sold me one (about $10 I think). When you plug it in it lets you know if your connections are correct, hot & working properly on your tow vehicle.
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Postby madjack » Wed Jul 25, 2007 2:01 am

Duane, I would run 10ga myself...and put a 30A fuse(per Joseph) as close to BOTH batteries as possible................ 8)
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Postby Gerdo » Wed Jul 25, 2007 2:06 am

Duane
I have a fuse then a solenoid wired with 10 awg thru a RV 7 pin connector. Works great. The solenoid disconects the trailer battery when the TV is turned off. That way it can't drain the TVs battery.
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Postby Joseph » Wed Jul 25, 2007 2:14 am

I use a combo six and four pin connector. The four pin is for the Scotty (no battery or brakes) and the six is for the teardrop. The center pin on the six (for brakes) is not connected.

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Postby diverguy » Wed Jul 25, 2007 7:30 am

duane,
i looked in my owners manual. 06 Yukon. and one of the pins was specified for charging a battery. so my camper wireing has a round 7 blade connector on it. it seems to work fine. and for safety reasons i just unplug the connector when i get set up to camp.
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Postby Alphacarina » Wed Jul 25, 2007 1:24 pm

I would put a small relay near the battery in the tow vehicle. Energize that relay with a wire from the ignition circuit and that way you're only connecting the tow vehicle battery to the tear battery when the engine is running . . . . that way, you never stand a chance of draining your car battery

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Postby Gage » Wed Jul 25, 2007 1:41 pm

Joseph wrote:
madjack wrote:Duanne, it is as simple as running a 10ga wire from the + side of the vehicle battery to the + side of the tear battery(with appropriate grounding)...

Don't forget the 30 amp fuse.
Joseph

At each battery. :yes:
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Postby Kankujoe » Wed Jul 25, 2007 4:16 pm

Gage wrote:
Joseph wrote:
madjack wrote:Duanne, it is as simple as running a 10ga wire from the + side of the vehicle battery to the + side of the tear battery(with appropriate grounding)...

Don't forget the 30 amp fuse.
Joseph

At each battery. :yes:


Anyone have a diagram with a fuse at each battery?
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Postby Alphacarina » Wed Jul 25, 2007 7:17 pm

The reason you want a fuse at each end is that if you chafe the wire and short it to the car or trailer frame, you could start a fire because you have hundreds of amps of curent available . . . . at each end

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Postby clkelley564 » Thu Jul 26, 2007 3:11 pm

Here are the parts you need:

Parts necessary from
http://www.radioshack.com/
1 ea. # 275-226 12VDC/30A SPST Automotive Relay, $6.49
1 roll #278-569 35-ft 10-Gauge Hookup WireBlack, $14.99
1 pkg #270-1084 25A Blade-Type Automotive Fuses, $1.99
1 ea. #270-1234 30-Amp Inline Blade-Type Fuse Holder, $2.49
1 pkg #278-1632 4" Nylon Wire Ties, $1.99
1 pkg #64-3111 12-10 Gauge Shrink Butt Connectors, $1.99
1 pkg #64-3140 Low-voltage Tap-Ins, $1.99
1 pkg #64-3120 Insulated Ring Connectors, $1.99
2 pkg #64-3137 1/4" Crimp-On Quick Disconnects, $1.99
Combo 7-pin Round/4-pin flat adapter with mounting bracket - Auto Zone $24.99


Here are detailed instructions:

Installation:
If your vehicle already has a trailer battery charge wire routed from
the 7-pin connector to the engine compartment, you can skip steps 1-5.
1. Disconnect the negative cable at the battery.
2. Jack up vehicle and support using stands.
3. Connect 10 gauge wire to "Battery Charge" pin of 7-pin connector.
4. Route the 10 gauge wire under the vehicle to the engine compartment.
Use tie wraps to secure the wire and keep it away from heat and
mechanical hazards.
5. Bring the 10 gauge wire up into the engine compartment near the
battery.
6. Mount the 30A relay near the battery using an existing screw, or
drill a hole for mounting.
7. Cut a 6" length of wire off the end of the 10 gauge wire.
8. Crimp a quick disconnect "female" connector to one end of the 6"
wire.
9. Crimp an ring connector to the other end of the 6" wire using a ring
with a hole large enough for the relay mounting screw to pass through.
10. Put the relay mounting screw through the ring connector on the 6"
wire and mount the relay.
11. Slide the quick disconnect connector onto the low current "ground"
lug of the 30A relay.
12. Locate the positive terminal of your battery.
13. Determine if the positive battery cable already has an unused 10-12
gauge auxiliary wire. If so, simply insert one lead on the 30A fuse
holder into the butt connector provided and crimp it. Skip to step 22.
14. Otherwise if there is no visible auxiliary wire, determine if the
battery uses top mount stud or side mount cables.
15. If it is a top mount stud, select a ring connector with a hole large
enough to clear the batter cable tightening bolt.
16. Crimp the ring connector on one lead on the 30A fuse holder.
17. Put the ring connector over the battery cable clamp bolt, re-install
the nut, and tighten sufficiently. Skip to step 22.
18. Otherwise if the battery uses side mount cables, follow the cable to
the starter solenoid. Disconnect the battery cable from the solenoid.
19. Select a ring connector with a hole large enough to clear the batter
cable stud on the solenoid.
20. Crimp the ring connector on one lead on the 30A fuse holder.
21. Put the ring connector over the solenoid stud, re-install the
battery cable and nut, and tighten sufficiently.
22. Cut a length of wire off the end of the 10 gauge wire long enough to
reach from the fuse holder to the relay. Leave enough to secure the
wire with ties.
33. Connect one end of the wire to the fuse hold using a "butt"
connector.
34. Crimp a "female" quick disconnect to the other end of the wire.
35. Slide the quick disconnect connector onto the high current +12V lug
of the 30A relay.
36. Route the 10-gauge wire from the 7-pin connector to the relay and
cut off leaving enough length to secure with tie wraps.
37. Crimp a "female" quick disconnect to the end of the wire from the
7-pin connector.
38. Slide the quick disconnect connector onto the high current negative
lug of the 30A relay (opposite side).
39. Crimp a "female" quick disconnect to one end of the remaining loose
10-gauge wire.
40. Slide the quick disconnect connector onto the low current positive
lug of the 30A relay (opposite the ground lug).
Now you have done the easy part ;-).
41. Locate a source of +12V switched by the ignition key (i.e. only
"hot" when the key engine is running). For older cars you may find that
another terminal at the starter solenoid will meet this requirement.
For newer cars you can call a local automotive electrical shop, or
possibly get a wiring diagram from the library or a purchased manual.
42. Use the "Low-voltage Tapin" to connect the other end of the low
current positive wire from the 30A relay to the source of switched 12V
power.
Carol
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2009 Ford Explorer Sport Trac 4.8 V8
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