Has anyone else thought to themselves that the wiring to and from the batteries in their trailer was a bit small?
I was wiring in a new battery disconnect switch between the two 6V batteries on my travel trailer, and without even thinking too hard about it, I decided that the 10 AWG wire I was using was too small, so I used a double run of 10 AWG (since I didn't have anything thicker handy). After that, I went looking at the positive and negative leads to the batteries. On my trailer, it looks like the previous owner has done some electrical work, because it's a mess of different colors. On both sides there is some 10 AWG, and some 12 AWG.

Considering that the inline fuse for the positive lead to my battery is 30A, I'm using that as an estimate of the max draw. And thinking of where my breaker panel is in my trailer, it's got to be 30 feet of wire before it gets there.

Anyway, clearly the existing setup works, I've had no issues. But it got me thinking about how if I was building it from scratch, I'd use thicker wires for the main leads.

Back when I was into car stereos, it was pretty common for guys to use '0' or '00' welding cable for power supply to the amplifiers, and I'm pretty sure they weren't running more than 30A, most were 15A if I recall.


So, I'm not really asking for technical assistance, just wondering who else has had these thoughts.

 

Batteries to converter? 4 ga. I carry a roll on my truck along with the ends to fit it.

Steve

 

Exactly. While I'm on the topic Steve, is to common to have an inline fuse on that battery-to-converter wire? If so, what amperage is common? As I mentioned, it looks like someone has been hacking up the wiring, so it's definitely not the way it left the factory, and the inline fuse is 30A.

I had a look, and the local farm and industrial supply store where I buy my wiring stuff only lists down to 8 AWG wire on their website. Although, thinking about it, applications like flatdeck or dump trailers etc probably have lower current draws than an RV. Unless that flatdeck had a winch . . .hmmmm.

Lots of food for thought. I don't really want to re-wire this trailer, but maybe I'll end up doing exactly that.

 

You will find some variation in fuse size so in part it depends on the ga wire you have, but a 30 amp fuse is probably the most common. With the little rectangular breakers they are generally 30s, but can also be 40s and there may be a fifty for the slides.

As you know, all the newer converters have two fuses in parallel for polarity protection, usually two 30s or two 40s on the converter itself.

When you actually amp the lead from the converter to the batteries, you seldom will see more than 20 amps when the charger is working.

Over the years, as power demands have increased by owners, ga. size has increased and now I almost always see 4 ga. I know that is more than required by amperage, but resistance over run length is also a consideration and I think manufacturers stick with one size given the confusion that might result from trying to change ga. size with each camper. I think on our little fifth wheel which is a 2002 model, only has 10 ga off the battery and a very short run to the converter. Our larger 08 model has 4 ga. batteries on one end, converter on the exactly opposite, before I installed the inverter/charger. I also see 6 ga on some of the older models.

Can you check your amp draws? Do you have a specific concern? What converter do you have?

Steve

 

I don't have a clamp meter to measure amperage. Really, I don't have a specific concern, I was just thinking about this a bit while I put in that battery disconnect. I'm an engineer, albeit in a very different field, so stuff like this gets in my head, and then I can't stop thinking about it. I have to resist the urge to tear things apart when they are working fine, like in this situation.

I actually have no idea what converter I have. I assume it's somewhere behind the fuse panel? I do have a stack of paperwork that the previous owner gave me when I bought this trailer, maybe it's listed in some of that?

 

It's probably a good thing that I can't store my trailer at my house. Otherwise, I would have most of it taken apart.

I'm all about over-engineering. If 8 gauge is acceptable then 4 gauge is better.

 

Man, be careful with that. You realize there is no stopping point. I carry 4 ga because I can cover everything with that. I know it is often way more than necessary.

Steve

 

This is a pic of the current solution. Doubled up 10 AWG between batteries, mostly 10 AWG from batteries to main panel with one spot of 12 AWG. will tidy that up soon.

 

You can always double up like you have done. It works, enjoy your camper.

Steve

 

1/0 gauge would be my suggestion no need to burn your **** up

 

So you would suggest 1/0 to carry 50 amps from the converter to the batteries on a circuit that is fused at no more than 50 amps?

How would you suggest hooking 1/0 to the converter and the 30 - 50 amp breaker?

Steve

 

Or 30A in my case . . . .
if a guy has 1/0 wire and appropriate connectors laying around, using it might make sense. Buying that size is a bit crazy.

 

try this

Wire Gauge Amps Ratings for 12 volt Automotive Systems

and this

measurement - Physically determine unknown wire's gauge - Electrical Engineering Stack Exchange

I know the run from battery in front of trailer to Main fuse panel is 40 feet.. and at a 20 amp draw.. I have a 0.6 volt drop.. so Coachman use the minimum to get by with.

and this after I install New ends every where in the Main supply .. and all connectors were Soldered by me. and a New 50 amp breaker at the battery.
and YES the 50 was the old one.. for a 30 amp system.


I really dislike the 0.6 volt drop.. so till more money is available for my trailer.. I replace 20 *1141* inside lamps (with LED replacements ) and replace outside lights with strip LED AT 1/4 the amp draw. .. all for 40 dollars and a little work.


FYI, I am using a calibrated Multi meter by Fluke.. it is correct.


MY View on my trailer..... Coachmen is Dumb.... front battery, rear fuse box, Front kitchen, Front Furnace. so every thing is run from front to rear and back to front. with voltage drop on every branch.


and there is a small storage area with door UNDER the refrigerator and next to the furnace .. with plenty of space for fuse box and converter... in the FRONT. also the water heater is next to the front sink... so ALL big 12 volt power users are up front.

 

Thought I'd post this mostly-related question here instead of digging out a different thread. I put in new brakes recently, and I noticed some of the factory wiring on this truck is crazy small. The wires that run from one side of the axle to the other are some kind of werid duplex double sheathed thing, and the conductor looks like it is 20 AWG or maybe even 22!
That seems quite small, even for the 3 Amps that it could carry.

Since I'm having some braking issues and may end up re-wiring the brakes, what gauge of wire would you use for a) the run from the battery to the brakes (carrying the amperage for all four wheels) and b) for the run to each wheel, carrying the amps for one wheel only?

I was thinking 10 or 12 AWG for the main run and depending on what I have laying around, probably 14 AWG to each wheel.

My local farm store sells 14 AWG dual conductor double sheathed trailer wire, or I may just use some of the primary wire I have laying around, although that would be less tidy.

Chucks link seems to suggest 14 AWG would be fine.

 

You'd likely be okay with 14 AWG. However, 12 AWG would be a bit better, IMO. 10 gauge would work just fine, too.