A question about my 12V system

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A question about my 12V system

December 08, 2010, 11:25:06 am

We have a Winegard Carry Out satellite dish that we use when trees get in the way of the Trac Star dish mounted on the roof. The electric power connector on the Carry Out is flimsy and a real bear to connect and disconnect.

I've been thinking about installing some sort of coupling device like the male and female ends of a household electric extension cord. I would do this so that I leave about 12 inches of the Winegard-supplied electrical supply cable attached. Doing a Google search (Google is my friend) I came up with a trolling motor cable. See photo. My concern about this device is that is make with #10 wire and so here is my question.

Will I be doing something negative to my batteries or put extra demand on the 12 volt system by putting a section of a much larger gauge of wire into the smaller gauge of wire used by Winegard? I can only guess that the gauge on the Winegard is probably 16 or 18.

Re: A question about my 12V system

Reply #1 – December 08, 2010, 11:33:48 am

George,

The short answer is "larger wire is good." Corollaries include, "if you use longer wire, it should be larger," "longer wire of same size is not so good, or maybe even bad," and "smaller wire is bad."

Re: A question about my 12V system

Reply #2 – December 08, 2010, 11:36:24 am

George,

No problem with the drain on your rig's 12volt system, it will be exactly the same as before as long as you use a heavy enough gauge wire. Measure the current draw or read the specifications and we can calculate the correct wire gauge for the length of cable. I advise against using 120volt connectors, as there is a danger of it being plugged into 120volts by mistake,

Re: A question about my 12V system

Reply #3 – December 08, 2010, 12:10:55 pm

Good answers.

And high quality water resistant electrical connections can be found at any marine store.

But, not sure a standard trailer two conductor connector such as this one would not work for you-- depends on the amp draw of the dish: http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=109505&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10611&classNum=10615

Brett

Re: A question about my 12V system

Reply #4 – December 08, 2010, 12:21:28 pm

Tom,

Great point. I had not thought of that. Love this forum.

Brett,

Your suggestion looks even much better than what I found. I keep forgetting that marine products often have good application to motorhomes. I've been in West Marine stores and they have some good stuff. Pricey, but good.

Re: A question about my 12V system

Reply #5 – December 08, 2010, 12:26:45 pm

Quote from: George Stoltz – December 08, 2010, 11:25:06 am

I've been thinking about installing some sort of coupling device like the male and female ends of a household electric extension cord.

It's a really bad idea to use electrical devices for something that they are not intented to be used for such as electrical power connectors. Sooner or later they get plugged into where they shouldn't be and then you have a much larger problem. This also applies to wiring a 120v device with 240 volts and vice versa, or any voltage it is not designed for.

Re: A question about my 12V system

Reply #6 – December 08, 2010, 02:20:34 pm

These connectors are also good:

http://www.rctoys.com/rc-toys-and-parts/PP-15A/RC-PARTS-CONNECTORS-WIRING.html

Re: A question about my 12V system

Reply #7 – December 08, 2010, 02:30:12 pm

I am going to use the 2 wire SAE connectors to hook up my solar panel. You can find them at trailer places and online solar stores. They come in different wire gauges and lengths. They are polarized and since they are intended for outside use they are fairly weather resistant. I would still use a grease or Corrosion X, etc. on them.

Re: A question about my 12V system

Reply #8 – December 09, 2010, 08:21:03 am

Anderson Powerpoles are a VERY good choice. They are available at various prices - do a net search. And you can make extension cords and equip other 12vdc devices with the same plugs and not have to worry about finding the "right" leads. I have used them for years and keep a healthy stock on hand.

Re: A question about my 12V system

Reply #9 – December 09, 2010, 08:34:44 am

This, from someone that thinks you should put tape over the wall outlets to keep the electricity from running out on the floor: Doesn't 12 volts in one end yield 12 volts out on the other end irregardless of wire size? Won't a 12 volt appliance only "ask" for 12 volts from a 12 volt source? Isn't it then a question of amperage instead? (WOW--big word for this early in the morning!)

Re: A question about my 12V system

Reply #10 – December 09, 2010, 08:44:09 am

nitehawk,

No, voltage "out" is not necessarily equal to voltage "in".

That is why there are different gauges of wire. Too small a gauge for the amps being carried results in a voltage drop over the wire due to resistance.

In fact, this resistance across a wire/grid is exactly how an electric space heater works.

Brett

Re: A question about my 12V system

Reply #11 – December 09, 2010, 08:50:02 am

Hey Brett,

Thanks. I was hoping you were on line. Your answers are more easily understood than some others.

Re: A question about my 12V system

Reply #12 – December 09, 2010, 08:59:41 am

I have a friend that was an electrician in a steel mill where heavy duty DC systems were frequently used. He once told me that when dealing with DC current, over sized wire causes extra resistance and can reduce the either voltage or amperage, I forget which one, at the outlet end." Bigger is better with AC current but not DC", does any of our experts know for sure if this is statement is incorrect? I have typically been pretty careful about using the right gauge of wire when wiring DC.

Re: A question about my 12V system

Reply #13 – December 09, 2010, 09:17:10 am

Quote from: Kent & Peggy Speers – December 09, 2010, 08:59:41 am

I have a friend that was an electrician in a steel mill where heavy duty DC systems were frequently used. He once told me that when dealing with DC current, over sized wire causes extra resistance and can reduce the either voltage or amperage, I forget which one, at the outlet end." Bigger is better with AC current but not DC", does any of our experts know for sure if this is statement is incorrect? I have typically been pretty careful about using the right gauge of wire when wiring DC.

Not True
Liquids flow through large-diameter pipes easier than they do through small-diameter pipes
(if you would like a practical illustration, try drinking a liquid through straws of different diameters).

The same general principle holds for the flow of electrons through conductors: the broader the cross-sectional area (thickness) of the conductor, the more room for electrons to flow, and consequently, the easier it is for flow to occur (less resistance).

Electrons flow through large-diameter wires easier than small-diameter wires, due to the greater cross-sectional area they have in which to move

Re: A question about my 12V system

Reply #14 – December 09, 2010, 09:33:14 am

Kent,

Barry is correct, your friend is NOT.

Here is a wire gauge chart for 12 VDC:
http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&catalogId=10001&page=Marine-Wire

Brett

Re: A question about my 12V system

Reply #15 – December 09, 2010, 09:47:31 am

Thanks again to my experts. It appears I got it backwards. After checking Wikipedia "http://en.wikipedia.org/wiki/Electrical_resistance", the resistance issue he described appears to be more related to AC current.

See what age does to memory!

Re: A question about my 12V system

Reply #16 – December 09, 2010, 10:59:19 am

I have become a better-educated motorhome owner because of the ForeForums and its predecessor at Yahoo.

Great explanation, Barry.

There is a wealth of information here. I am glad I asked my question.

Re: A question about my 12V system

Reply #17 – December 09, 2010, 10:12:43 pm

Sorry but the "engineer gene" in me needs to respond to the question about wire size and current flow. AC current has something called "skin effect" which can cause issues with current carrying capacity. This effect is so noticeable at microwave frequencies they often use pipes, called wave guides to pass the current.

See: http://en.wikipedia.org/wiki/Skin_effect

Re: A question about my 12V system

Reply #18 – December 10, 2010, 09:42:50 am

Hey John,

Thanks for the enlightenment. Is that similar to the "twin-framus phenomena"?

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