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1/0 alternator cable path under truck

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Does anybody have experience where two 1/0 high amperage cables should be run safely under a 2015 ram3500 dually megacab? I want to provide two output sockets in the rear bed next to the 7 pin trailer wire and it will require up to 25’ of cable from the alternator.


This is a follow on from my two earlier posts. I found a 270A alternator which is the same frame as the OEM Mopar. It has original Denso parts built by a specialty outfit in FL. The idle output is 200 Amps and peak is 270A. 


The external viltage regultor is from the marine industry and the two places have worked together before. There is also current limiting on the regulator gauge which can be dash mounted.

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Just make sure the insulation sheathing is rated for oils and you tie it well enough to stop all rubbing. I also think about some type of wire protection jacket like the flexible split plastic they sell at auto parts stores if it will come large enough to help cover the wire size.


I have seen some great items at a big rig store for truckers. There is a lot of high amp switches and associated electrical items there too.

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Thanks Jag1, appreciate the comments. That’s essentially what I am planning.


I'm using the AWG 1/0 DS18 CCA (copper clad aluminum) wire which is very flexible and has thick insulation. Plan to use two runs in parallel encased in plastic.


The only uncertainty is the exact path...

Edited by Shayne

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Now I see...  certainly inside side of the frame for best protection, but perhaps running along the passenger side staying away from fuel lines and tank?

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Hey Shayne...If your looking for maximum current delivery at the end of a 25 foot run of cable then you should review the composition of the material being used to conduct this current. The formula for this is also Basic Ohm's law as P= I^R 

Current itself, is evenly distributed through the cross sectional area of the conducting cable so the resistance of copper-clad aluminium is higher than pure copper. I don't know how much current you're expecting at the far end? I'm assuming with the plan of 1/0 Gage that you plan on providing a considerable amount of available current. You need to ascertain what your total current demand is at the remote location. You will then be able to formulate the losses on your selected cable and determine "if" it will be acceptable. 


Current demands of any system or "load" above 50 Amps begins to become a serious endeavor in a 13.8 Volt DC delivery layout. Seat-of-the-pants evaluation is, "Once you have every device drawing current at operational level and you can touch the insulated conductors and sense "heat" you have a considerable amount of power being lost in the conducting elements themselves" 


This loss is the voltage drop within the conductors due to the inherent resistance of the cable. You will see this on a test measurement from one end to the other. So....if you're imposing 13.8 volts at the input and you measure 12.1 at the far end when fully loaded at the demand current your voltage drop is 1.7 volts. Looking at this with an example load figure of say 100 Amps then: P= E*I or 1.7*100 = 170 watts being dissipated in heat.


The starter motors for the CTD can sink from 450 to 700 Amps depending on the temperature of the block and oil thickness. The cable transition of 1/0 from the battery to the starter is less than 6 feet but, the demand (or on time) of this power is of short duration. This loss is acceptable for the circuit....living comfort in your 5th Wheel maybe a different.


The bottom line is, "Can the electronic instrumentation tolerate a low voltage condition" when you're activating the device(s)?


If you can double the Gage thickness of the cable it will provide twice the current handling capability, with half the loss. Pay attention to composition of the cable, the manufacturer's specifications of the cable will recommend maximum expected levels and you're losses.


A 25 foot run of cable at 13.8 volts expected to sink 100 Amps with minimal voltage drop is a pretty serious demand...I applaud your plans...it is not for the faint of heart.  :wink:         

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Thanks for this insight WT, much appreciated. Here is where we are up to:


We purchased pure copper conductor - two runs of 1/0 for the run from the alternator to the rear bed, and also installed a thick triple copper connector cable for the length of the RV to drop resistance wherever we can. Using 


The only place left with dual 1/0 CCA cables is a short run at the front of the RV which was installed when it was opened up last year and I’ll keep an eye on that.


We have purchased a Balmar marine regulator for the truck, and a Balmar smart gauge which will be installed in the RV,  and also a data logger and some current transducers to monitor the current in the parallel battery strings.


There are also several cat5 cables which will carry the data reporting current charge or discharge.


the rig is also at the shop presently while they cut into the rear cap and install a hatch into the rear cap And we will mount waterproof RJ45 data sockets for the data cables to plug into.


the whole thing should be complete in about 3 weeks.

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