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Battery Cable size for Kill Switch

This should help in determining the proper wider gauge to use for pretty much any application you might have, (Just click the link):

Wiring Size Guide

Also, further info - General wiring rules of thumb:

*When modifying a factory circuit, you never want to use smaller size wire.

*The higher the amperage to be carried, the larger the wire needs to be, (Fairly obvious to most people)

*The longer the wire, the larger it needs to be, (Not nearly as obvious to most people but every bit as important!)

*Ground wires should be the same size as the positive wires unless they are considerably shorter.

*Every connection in a circuit causes either voltage or amperage loss (OR BOTH) Limit the number of connections/splices as much as possible.

*For optimal function, you should never run power wires in close proximity parallel (Along side of) wires used for things such as antenna, speakers if you can avoid it. If you must do so keep the length of the parallel runs as short as possible.

*Keep audio, antenna and data cables as far from engine ignition system components as possible.

*In vehicle electrical systems the negative (Ground) is just as important as the power. Provide a poor ground and you will get poor results. A good solid CLEAN ground will provide for brighter lights, longer life of any electric motor (Like your starter)

*All circuits should be fused for safety and that fuse should be located as close to the original power source as possible.

*Never replace a fuse with one of a higher rating, (Should go without saying, but I see it all the time).

*Most switches are not rated for more than a few amps, usually in the range of 5amps or less. When installing "Stuff" be sure you know the load your putting on the switch and use a good quality relay if you are even close (75%) to the rating of the switch.

*It should go without saying but you always want to protect your wiring from any moving parts. From vibration, excessive heat. You can get split loom from most auto supply houses and NAPA sells it in several sizes in 50 and 100' rolls. For a professional looking job, I always use spit loom on 100% of the wire run, from terminal to termination, just like the factory does. It looks good and protects the wiring.

*Use a good quality crimping tool to insure the best quality termination for your wiring jobs. Like this one, (Available at most auto parts houses only costs about $20.00) Ratcheting terminal crimper It works MUCH better than and gives much better quality terminations than the $5.00 tools that look like this one: "Heavy duty crimper"

*Use QUALITY crimp terminals. There is a big difference between a quality terminal and the cheap ones most auto outlets sell. The NAPA Belden brand ones are a good place to start. You can also get ones that have a solder ring built in and heat shrink tube. You crimp them then hit with a heat gun. That melts the solder and shrinks the tubing for a very professional almost weather proof termination. For a true weatherproof termination crimp terminals with a silicone like materiel, that melts when you hit them with a heat gun then solidifies when cool is available, (These also have the heat shrink tubing).

Hope this helps.
 
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gimpyrobb

dumpsterlandingfromorbit!
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You might be able to switch the #10 circuit, but if you put the cut-out on the negative to the batterys, you will never need to pull a battery terminal to work on the truck again! Any time you do something to your truck that requires disconnecting your batterys, just flip the switch and your golden.
 

maccus

Super Moderator
Super Moderator
Something for you M800 5 ton folks that might want to add a battery shut off switch. If you use the 24v positive side to switch remember that you have a wire that goes to the center of the two batteries as one of the functions on the M800s uses 12 volts. So when you switch the 24v line off the battery you will still have the 12 volts HOT on the truck.

Work smart and switch the ground (negative) line. And gimpyrobb's point is well taken.
 

Beerslayer

Well-known member
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I posed the question earlier of why it was important to break the negative side rather than the positive. I understand it now and am going to change my setup. I didn't realize that any 12vdc was being used on my m923 until I put a battery disconnect into the positive side and the heater fan still ran. So thanks for the ^^ excellent answers!

I apologize for what may seem like a thread hijack, but I can't help but notice an apparent conflict.

On one side there are the Military Purists who feel that any deviation from the way the military specified and maintained the trucks is Deviant Behavior and very bad.

Then there are those that think that these trucks as we find them are a wonderful starting point towards something greater.

Somewhere in this mix are those who vociferously oppose pulling an uneven load from batteries connected in series as being very bad practice and science. Yet it is for the first time apparent to me that the military does that very thing, and a fan load is not insignificant.

So is it OK if the military pulls 12vdc off of one of two batteries connected in series, but not OK if a civilian does it to run a radio?

If one 'improves' the system by installing a separately derived 12vdc system for all 12vdc loads then one runs afoul of the purists.

Is this a no win?
 

gimpyrobb

dumpsterlandingfromorbit!
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I live by the motto, its my truck, I will do as I please. Why do something to appease someone else? I think its great that some keep them stock, and I think its great that others make the trucks meet their needs.

You can pull loads off one batt for 12v. As long as you understand it will shorten the life of your batterys, go for it.
 

peecook

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Anyone know a good source for 2/0 Battery Cable? Even Saturn Surplus only seems to carry up to 0-gauge. The only place that I seem to be able to find it is on flea-bay. I know no place local (or with-in 1 hour of me) carries it, as I couldn't even find 0-Gauge battery cable for another project back sometime ago.

Thanks!
Any car stereo shop should carry it.
 

Katahdin

Active member
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I have my switch between the two batteries, I know it works because I had to yank the original dog bone to shut down my starter when it got stuck cranking away. Is there any argument against placing it there?

By the way, you can get 0/2 battery cables at Tractor Supply. I've also had them made at a local battery shop.
 

JasonS

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See that's what I was thinking. I wonder why some people used smaller cable... price I would guess. But it's not worth it if its going to cause problems later.

Thanks!
Because it is really not THAT critical for most people's usage. I kept the #2 cables when I converted from gas to multifuel. Didn't have a problem until it got to down to 4F and the short #4 cable between the two batteries got hot. Replaced it with a short #2 and it works fine. 2/0 will certainly perform better in cold weather but for most it is overkill. If you want to do it the right way, calculate voltage drop under maximum load and select the cable size that meets your requirments.
 
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