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Author Topic: Battery Power: Running both Positive and Negative  (Read 9119 times)

Posts: 15


« Reply #30 on: March 15, 2005, 06:21:36 AM »

There are many ways to approach this. I originally ran a fused lead to the battery. WB8FPQ, who wrote Damlier-Chrysler's manual on mobile radio installation, advised me to run an unfused negative lead to the chassis, close to the battery ground tie-in. This provides as low-ohmic connection as a direct battery tie in, but avoids the possibilty of your rig becoming the ground path for the starter should the battery lose its bond to ground.

Posts: 5480


« Reply #31 on: March 15, 2005, 07:07:08 AM »

KE8YY wrote:

> run an unfused negative lead to the chassis, close
> to the battery ground tie-in.

That's about the best compromise I've heard so far, the only criticism I have of that is potential resonances on the ground lead on HF.  This would be solved by grounding the chassis at the mounting point, and if you feel better running a negative lead as KE8YY proposed, that's fine too.

Mark K5LXP
Albuquerque, NM

Posts: 17476

« Reply #32 on: March 15, 2005, 01:03:53 PM »

1 Farad capacitors?

Actually they are pretty common these days.  Most commercial
sources carry them.  Often they are used in place of batteries
for temporary power backup of low-power circuits.  The ones
rated 5V are less than 2" diameter and 1 1/2" high (and
getting smaller all the time.)  So the technology is out

Even if you wanted to make your own, conventional 1000uF
electrolytic capacitors are available that are less than
1/2 inch in each dimension.  A thousand of those would be
less than 5 inches cubed.  Though I don't think I'd like
to take the time to solder them together.

A Farad isn't what it used to be...

Posts: 14491

« Reply #33 on: March 16, 2005, 08:00:27 AM »

Many of the newer vehicles have a ground stud on the fender, near the battery. The battery negative terminal has two wires on it, a heavy one to the engine block for the starter and a smaller one to the ground stud on the fender. This ground stud makes a good place to connect your radio's negative lead. If you make the connection at this point then the negative lead fuse is not required.

Bob  AA4PB
Garrisonville, VA

Posts: 1146

« Reply #34 on: March 17, 2005, 10:20:44 AM »

I originated this thread of discussion to pull together advice on running battery power to the rear seat of the crew cab of my 2004 Chevy Silverado 2500HD pickup truck.

Well, the deed has been done.  Yesterday (Wednesday, March 16th) I had the install done by the local Car Toys dealer.  I am very pleased with the results -- very professional work.

So, what was done....

(1)  Positive and Negative #4 cables run from the battery to the rear seat are of my truck.  These cables run under the cab along the frame, nestled up and out of the way of any kind of road hazzard problem.  Up through the floor board under the seat to two distribution blocks, one for positive and one for negative.  The distribution blocks allow for tieing in 4 other wires if I want.  Both positive and negative is fused at the battery location.

(2) Ground straps placed all over the truck.  First, the negative ground of the battery was already strapped to the engine block which was also strapped to the main chassis frame up front.  I also had a ground strap placed on the negative distribution block to the chassis frame.  And, a ground strap between the truck bed and the frame.

(3)  Antenna pass-thru connector in cab so that I can remove and replace the antenna at will.  This is also protected from the weather due to the design and construction of the cab itself.  I have easy access to this for the inside and on the outside.  I have devised a weather protection cover that is water tight that fits on the outside when I do not have my antenna hooked up (as it is right now).

(4) By the way, all holes and other pass thru areas of cables and things listed above are sealed with silicone rubber (the kind used for this purpose on cars).

(5) Audio feed cable that runs from under the rear back seat to the GMC Auxiallary audio coupler for my truck speaker system.  Also, this goes coupler handles output audio for pre-amp levels or powered speaker levels so it is quite flexible.  By the way, this was the single most expensive part of the work at $100.  One nice thing about this is that the audio feed is the aux input so I can switch between the truck radio/cd player and the transceiver by using a "mode" button switch there on my truck radio.  It goes like (AM, FM1, FM2, CD, AUX 1, AUX 2).

I am using an Icom 706 with the base unit placed under the rear seat in the back and the remotable front control panel up front.  The only things I have done yet are to finish building my antenna mount.  I am building a special aluminum mount that fits into the tie-down slot on the rear of my truck bed.  Also, I am going to probably put a water-proofed SGC auto-tuner right there at the base of the antenna mount.  And, of course it too will be easily removable.  The aluminum mount will be 1/4 inch thick so it will be nice and sturdy (it is not very big physically).

I have done one test and that was of the audio system.  I put my ic-706 on the back seat but I ran a coax to my Traffie Hex beam (through the garage, through the basement, and into the back where I have my transmission line pass through box (see my web site).  So, audio works and no RFI from the truck but it was only idling so this may not be the best test for that so far.

Thanks to all who have provided advice for my little project.


Posts: 14

« Reply #35 on: March 22, 2005, 07:42:10 AM »

I enjoyed this thread thoroghly. I too have wrung my hands over these issues. I live in the Pacific NW as well. I am the guy who against all odds believed the installers and accepted what they recommended for my mobile rig insallation. No Neg. lead from the battery.
I run a TT Scout and a Metron w/o any supplementary battery. I drive a '98 Toyota Corolla. I've had it in use for about two years. No problems, it's all good.
I am entirely pleased with my mindless approach. I feel as though I'm running with a pair of scissors in my hand, but that just makes mobiling all the more fun.
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