Author Topic: Power/ground distribution blocks...or wire gauge reducers....help?  (Read 5279 times)

Offline machinisttx

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I lucked into a deal on a few feet of 3/0(huge) battery cable, and I think it will be long enough for what I want to do with it....which is bringing a substantial single power run into the cab of my truck for distribution to comms gear/inverter/etc.. The biggest problem I'm running into is that all of the power distribution blocks(car audio oriented, fwiw) I'm running across are only stated to be large enough to handle 1/0 cable at the input. I refuse to trim strands of copper to make it fit, so I started looking at cable reducers....and product descriptions seem pretty limited on those. Am I going to have to buy some copper bar/round stock and just make what I need or have I been looking in the wrong places?



FWIW, I would never have used actual battery cable for this if I hadn't gotten it so cheap. Welding cable is like a million percent better in every way conceivable.

Offline Fixit

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #1 on: June 03, 2017, 03:58:50 PM »
Like you I could not get past 2/0 on a junction block . I then thought what did I do for that guy with the long 24 volt solar run a few years back .

https://www.amazon.com/Fastronix-250-MEGA-Fuse-Holder/dp/B015ABMN6C/ref=sr_1_5?ie=UTF8&qid=1496526679&sr=8-5&keywords=amg+fuse+holder

Use a copper lug and a agm fuse holder with proper size fuse for your needs . Just keep spare fuses on the truck . in with the 3/0 and out with what ever size you really need .


Offline machinisttx

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #2 on: June 03, 2017, 07:08:50 PM »
I used a Blue Sea ANL fuse holder when I replaced the "big four" in my jeep. It replaced the failtacular fusible link.  Thanks for the suggestion.  :) The "mega" fuses are available at oreilly's, if anyone else interested finds this thread. Only place I can find ANL fuses locally is West Marine.

At this point it's looking like I will have to machine out some custom parts to get the wiring as "clean" as I want it. Copper stock ain't cheap.  :'(

Offline Carl

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #3 on: June 03, 2017, 07:57:47 PM »
  Route the cable carefully as many cables do not work well in the high underhood heat.
3?0 cable will handle 300 amps at 15 feet.
You can use soft copper to make end fittings(lugs) and an electrical supply shop can supply such heavy distribution hardware in COMMERCIAL ELECTRICAL rather than Residential.
If voltage drop is a worry ,use onlt ONE wire and pull ground from the body or frame of the vehicle to cut losses in half.

My best thought on this subject.

Offline machinisttx

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #4 on: June 03, 2017, 10:19:41 PM »
You're right about the insulation on some cable, though this is actual SAE J1127 SGX spec battery cable. Supposedly resistant to everything that you'd expect to find in an engine compartment and a few things you wouldn't. I will check the local electrical supply houses to see if they have something like what I have in mind...hadn't thought of that until you mentioned it. Thanks!  :) I don't think I'll have to worry about voltage drop. 1 gauge or 0 gauge would probably be more than sufficient for what I have in mind. What experience have you had with ground loop problems in comms or audio gear? I'm hoping that by running power/ground for everything directly to the battery I'll avoid any issues of that sort.

Can you explain how running a single cable would reduce losses? I would think that direct to battery would have lower losses than routing ground through body/frame?

Offline Carl

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #5 on: June 04, 2017, 09:45:36 AM »
You're right about the insulation on some cable, though this is actual SAE J1127 SGX spec battery cable. Supposedly resistant to everything that you'd expect to find in an engine compartment and a few things you wouldn't. I will check the local electrical supply houses to see if they have something like what I have in mind...hadn't thought of that until you mentioned it. Thanks!  :) I don't think I'll have to worry about voltage drop. 1 gauge or 0 gauge would probably be more than sufficient for what I have in mind. What experience have you had with ground loop problems in comms or audio gear? I'm hoping that by running power/ground for everything directly to the battery I'll avoid any issues of that sort.

Can you explain how running a single cable would reduce losses? I would think that direct to battery would have lower losses than routing ground through body/frame?

I know that single cable for power has less loss because vehicle body or frame is a bit lower loss than as size cable that you would use,this is why few things are wired to BOTH battery terminals,especially high current demanding equipment as you use HALF as much wire. I see very little mobile equipment develop ground loops as they are now designed with a negative side ground buss,but often had such problems with audio especially in the early days of mobile electronics.

  I even found and fixed a problem where a renter said her shower made her TINGLE...after initial jokes about her soap,I discovered the 'updated' electrical system had TWO fuse-boxes/circuit-breaker panels INCLUDING ground rods for each box and the GAS water heater had been replaced with electric water heater...one of the heat elements allowed a charge on the water while the shower drain (all metal pipes) went to ground...but not the same ground as the water heater...wet woman was the conductor...thank someone they didn't have a salt water softener to provide better conduction.

Mystery of tingly shower fixed by relocating ONE WIRE in circuit panel and my father kept his shoes on while 'tingle-testing' the shower or his pace-maker would have had a fit. GROUND is not always ground and multi-panel distribution is not a good idea.

How much more 'direct' a connection to the battery can you have when the auto body is where the battery is first tied to and ....should your negative cable suffer from corrosion (due to moisture and dissimilar metals) what will happen to the device that will have to pass ,say your starter current? The body or frame of the car is best though the positive wire to battery is OK,if you don't mind corrosion from acid/heat/and oil/fuel grime ...most vehicles have a fuse block with a high current BATT or battery terminal to have a cleaner,more secure main connect to the battery.

My Ham gear id Positive to the battery and negative to the frame as it was easier for me and BOTH wire + and - are fused for safety...don't forget the fuses.

Just my thoughts, feel free to do as you please as I could be wrong.

Offline never_retreat

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #6 on: June 04, 2017, 01:08:36 PM »
They do make such a critter for electrical wiring. Common trade slang is a tit or nipple. (laugh all you want)
You will need a big hydraulic crimper, or you may be able to try an solder on with a torch.


Offline Carl

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #7 on: June 04, 2017, 04:38:17 PM »
 :rofl:  I have seen the third one, 90-350 before....

But it seriously best to avoid a hot spot by leaving all conductors intact till distribution block is reached or you wind up negating the circuit value of having a large wire with a ,even short,reduction in size as DC current (just as radio transmitted RF) travels on the outside of the conductor while AC current travels INSIDE the wire/conductor.
« Last Edit: June 04, 2017, 04:44:27 PM by Carl »

Offline machinisttx

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #8 on: June 04, 2017, 04:53:21 PM »
Carl, my thoughts on passing current through metal are based on welding. The farther the ground(or work, if you prefer) clamp is from the area to be welded, the higher the current loss, especially if corrosion or some other impediment is present.  Steel is only about 15%(at most, from what I'm finding) as conductive to electricity as copper, so I cannot see how a ground to the frame is going to lose less voltage/current. I'm scratching my head on this. I'm thinking that having one or two cables(and connections) going to the engine bay and exposed to that environment is much less to worry about than the 10 or 12 that would be required to run everything I have in mind directly to the battery. I will definitely be fusing in at least two locations, and each component has it's own fusing, so several layers of protection. I may end up also adding an inline switch or solenoid to cut power on that cable altogether.

Cable size will not be reduced until it gets to the distribution blocks, from there it will be broken down to whatever is appropriate for the device.

never_retreat: I saw those somewhere, but evidently didn't hit on the right search term. How big of a crimper is needed? I think mine is 16 tons and has dies up to 4/0. If needed I will machine some dies and use the 50 ton shop press at work...plenty of scrap steel laying around for that.  ;D  I usually do both solder and crimp on battery/starter/welding cables...but I really only put the solder in to seal the connection(after crimping), and then put dual wall adhesive heat shrink on for a complete seal. Anyway, after looking through their site, I found what I needed. Thanks!

Offline Carl

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #9 on: June 04, 2017, 06:13:00 PM »
  Running one heavy,and better conducting copper wire to a distribution block (for negative) or maybe marine fuse block will do fine as I have done this on boats...I keep falling back on single ground and all other wires as HOT is maybe more my habit from mobile installs to save wire and lessen loss due to too small of wires used by Ham manufacturers these days. I also do run devices and check for voltage drop as near the radio or amplifier as I am able to help eliminate loss...and heat.I only am telling you how I do it,not how I expect you to do it. You appear to have a good grip on it now, good luck.

Offline never_retreat

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #10 on: June 04, 2017, 06:37:43 PM »
Carl, my thoughts on passing current through metal are based on welding. The farther the ground(or work, if you prefer) clamp is from the area to be welded, the higher the current loss, especially if corrosion or some other impediment is present.  Steel is only about 15%(at most, from what I'm finding) as conductive to electricity as copper, so I cannot see how a ground to the frame is going to lose less voltage/current. I'm scratching my head on this. I'm thinking that having one or two cables(and connections) going to the engine bay and exposed to that environment is much less to worry about than the 10 or 12 that would be required to run everything I have in mind directly to the battery. I will definitely be fusing in at least two locations, and each component has it's own fusing, so several layers of protection. I may end up also adding an inline switch or solenoid to cut power on that cable altogether.

Cable size will not be reduced until it gets to the distribution blocks, from there it will be broken down to whatever is appropriate for the device.

never_retreat: I saw those somewhere, but evidently didn't hit on the right search term. How big of a crimper is needed? I think mine is 16 tons and has dies up to 4/0. If needed I will machine some dies and use the 50 ton shop press at work...plenty of scrap steel laying around for that.  ;D  I usually do both solder and crimp on battery/starter/welding cables...but I really only put the solder in to seal the connection(after crimping), and then put dual wall adhesive heat shrink on for a complete seal. Anyway, after looking through their site, I found what I needed. Thanks!
I think the crimper I have is 12 tons and does all the way to 750mcm. Its a hand held hydraulic. It has 4 jaws that press in from the sides no dies needed.
Take a look at these as well if you don't want to crimp.
https://commerce.ilsco.com/e2wShoppingCatalog.aspx?parentId=3100012930&parentLink=2100001183:3100012318:3100012319:3100012930
https://commerce.ilsco.com/documents/PDF/TechnicalDrawing/M2492.pdf

Offline shadowalker_returns

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #11 on: August 21, 2017, 04:16:11 PM »
  Route the cable carefully as many cables do not work well in the high underhood heat.
3?0 cable will handle 300 amps at 15 feet.
You can use soft copper to make end fittings(lugs) and an electrical supply shop can supply such heavy distribution hardware in COMMERCIAL ELECTRICAL rather than Residential.
If voltage drop is a worry ,use onlt ONE wire and pull ground from the body or frame of the vehicle to cut losses in half.

My best thought on this subject.

The short answer is goto any decent marine supply outlet and get lugs and distribution block of appropriate size. Blue Sea Systems makes excellent ones.

Hooking your grounds to the body or frame does not cut your losses in half. The current path on a vehicle is always from the source back to the source. If it went out 20 ft its return path will most likely be twenty feet. The current path you calculate for is the total of distance from the power source to the power source. The reason auto manufacturers and others use the body/frame of a vehicle for the return side is simply cost. The amount of copper saved decreases their cost and increases their profits. It is not the ideal solution. The IEEE and SAE have literally hundreds of studies showing the problems caused by multi-point body/frame electrical return signals. The reason they get it to work reliably is the amount they spend on engineering to reduce the effects of return paths on conductive noise and rigorous risk analysis (and sometimes they still get it wrong). Single point wiring is not the same as single wire grounding. For most applications that are not low level signals or sensitive RF signals, single point grounding is overkill as it will nearly double wiring cost.

For you I think the best solution since you have the wire available is to run a both a source and return line to at least your first main power distribution point/box. this has many other benefits as well such as reducing the potential for ground loops and full or near full current shorts.

Here is a simple tip: when running that cable twist them together in a simple two wire braid. It will cut noise collection/production significantly.

As I was reading Carl's post I was reminded of a Electrical Code requirement for only a Single Ground Point in Residential and commercial construction. His shower example is a prime example of why. Some quick background. For a building's ground to be truly effective it needs a direct path to the Earth of less than 3 ohms resistance (the spec we use is 2 ohms).  Most grounds don't achieve this without a little help. If you establish only one ground and its value is a bit off there is usually no worry. If you establish more than one ground then the electric current will take the path of least resistance. In the case of the shower there were two or more active ground/return paths of differing value. When the lady had her shower 'on' that path had a lower resistance than the correct path. The differences were probably very low (less than 3-5 ohms), we know that cause nobody died. That tingling was actually electrocution. just not enough current flow to turn the heart off. She don't know it but Carl and his Dad just might have saved her or her family members life. House wiring (though simple) is not a joke. Remember in the professional world of electrical/electronic engineering and practice anything over 50 volts is considered High Voltage!
If your doing any high voltage wiring in your home or anywhere and your not absolutely sure about something, ask! If you've got a friend (like the lady had Carl :)) they won't mind.

Regards,
Shadowalker

Offline Carl

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Re: Power/ground distribution blocks...or wire gauge reducers....help?
« Reply #12 on: August 21, 2017, 06:02:01 PM »
  She was never as clean as when she was 'power washed' in the shower though.....