I have a winch on my trailer that uses a car battery.
I want to run a constant feed to the battery when ever the trailer is plugged into the truck. I remember someone telling me that there is one wire i can use thats already in the plug for a 12v source.
Has any one ever done this? If possible i want to only use the 7 prong plug. I know i could always run a feed from the truck battery to the trailer battery but thats sloppy.
I think i described exactly what i am thinking about. When i want to winch something on my trailer ill start my truck and power up the winch. this way i dont have to charge the battery the day before and it will always be at full power.
this is the plug i have on my truck for my brakes and lights
you might burn up the harness. Find someone with old car stereo wire (4awg or 2awg (100 amps)) and run it from your battery. 0awg (250amps) is preferred, but the winch can’t possibly draw that much… I don’t think.
Do you know how many amps your alternator is? You’re going to lose some power with a wire that long, but it won’t matter if your alt is over 90amps.
I don’t think any of the wiring coming out of the 7 pin is going to be up to the amperage draw of a winch. I’ve taken the 7 pin apart on my truck and none of the wires are a decent gauge.
^ I’d probably just build that myself, but it gives you an idea of what you need.
If you have a battery on the trailer and put a fuse in line shouldn’t it be ok?
Couldn’t he just use that 12 volt source as a trickle to charge the batteries?
Think about a 5th wheel RV. They have TV’s, fridges, electric stoves etc, and all they have is the standard plug in.
I say mount 2 batteries and run the 12 volt source to the battery you’re not directly feeding off of.
A typical tow vehicle, for example my 1996 Dodge RAM 2500 HD, has a 130 amp alternator. Normal electrical use in the truck is much less, leaving plenty of excess capacity for charging trailer batteries. But in fact, I found that I got only about 5 amps of battery charging when my trailer batteries were low, and less than that when the batteries were charged to above about 70% of capacity.
The poor charging is due to the voltage drop in the long run of skinny wire from the truck alternator back to the trailer battery (probably about 25 feet).
If you need more then a slow charge you need to run thicker lines.
We ran a seperate 4 or 2 ga wire from the battery to the back of my dad’s truck for this purpose. But we used a seperate connector dedicated to the winch on the trailor that’s only plugged in when we’re using the winch just due to the current draw (depending on the size of your winch of course).
I’d say look at what the current rating on that connector is; then what’s the “max” draw on the winch; that’ll tell you if you’re safe or not.
I think the only problem with that system would be if you drained the batteries. Then the fuse would pop as the electric motor would try pulling xx amps through the skinny trailer wire.
This is why you really really need to have it fused in my opinion. This is also the simplest way to do it.
I would go 0ga with a 200 or 250 amp fuse. you have a long way back to that back battery so the bigger the better. U just need to find a weather proof connect that accepts 0ga.
Mount a deep cycle on the trailer. Charge it before you go. Or charge off the 12V feed on the RV connector. Use a diode bridge (isolator) to protect the vehicle battery.
Public service announcement: Always size your fuse below the maximum ampacity of the wire. Fuses protect wires, not equipment. So a 4 gauge wire should be protected with a 100 amp fuse.
