I already have around 60 ft of welding cable in my truck, I just picked up another 30 feet to do another run of positive to the back because I'm about to install dual alts. Would it be better to run 2 neg runs to the front and back batts or just ground at each end?

Ground directly to the frame in the front and rear. Also ground the alternators to the frame.

Absolutely !!! Shortest lengths possible ...

Sweet thanks guys!!!! What Is the best way to run a cable through the cab floor?

Edited December 28, 201113 yr by Dangrebel

I use a 1/2 inch steel rod and a hammer to indent the fire wall or floor. I then double check the opposite side to make sure I won't hit any wires or brake booster, ect. The indention will help the drill bit from walking also. I use a stepped drill bit to drill my holes, then insert a gromet and caulk the hole after the wire is ran. If you use split loom to cover the wire do not run it all the way through the hole into the cab because water can run between the loom and cable and go into the cab.

Nice tip Q.

Hell yea, y'all got me all excited now thanks for the info

Excellent tip Quentin!

Even with frame grounds I have heard where it helped to do a negative run from front battery to the rear battery. If you have the wire then go for it but if not then no big deal, you can never have to any grounds.

Why not run your ( + ) lengths to the battery bank, then ground the bank in the rear and test? You may just find that to be satisfactory, saving yourself time and money. You could use the cable you saved for things like upgrading the big 3 on any other vehicle you may have, or help out a buddy with their big 3. You could also make yourself some jumper cables / welding leads and use your alt to weld something up if you or someone you like has an emergency. Good luck with whatever you decide and don't forget to keep us posted.

Absolutely !!! Shortest lengths possible ...

It still has to go through the frame and if cable is plentiful I'd rather see a run of negative too. See hardcore Street A and B cars...they all have both ground and positive ran directly...

Absolutely !!! Shortest lengths possible ...

It still has to go through the frame and if cable is plentiful I'd rather see a run of negative too. See hardcore Street A and B cars...they all have both ground and positive ran directly...

I have my truck done with 1 run each of + and - to the front battery.

Yea that's what most people do that I read about. Could I run my amp ground to my neg batt post?

Yea that's what most people do that I read about. Could I run my amp ground to my neg batt post?

yes

BTW.... lets see some videos bro!!!

Just remember, no copper wire you can feasibly put in the car will have less resistance than the frame. Most people just don't bond to the frame properly...

I do not know your entire electrical setup or else i could go more in depth accurately..

For one, you say you have dual alts.

Ground each one of these to the frame as short as possible.

Next, run 1 power cable from one of the alts to starting batt..

Next, run at least 1 power cable off of each alt to rear.

Ground battery bank in the back properly.. there are several ways based on wiring configuration.

Next, run 1 and only 1 ground cable from the rear battery bank directly to each alt case OR the ground point where each alt is grounded too.

If you do not do that last step, once a load has been put on the electrical system from car audio(substantial load), your up front voltage vs rear voltage will always differ.

In every vehicle i have tested this including mine, rear voltage, i've seen has been as high as 0.9v lower than front, lowest i've seen is 0.3v!

That's still a lot!

When you first start car or driving, the voltages are equal typically. But once a substantial load has been put on it, then you see the real world voltage drop in the rear that will always be there..

So, if you do not wish to run this ground cable.. then go out and test your front to rear voltage after you have put a good ~20-30sec load on the setup.

Measure at alt's power stud then at amp's power terminals and report back.

run that welding cable under the truck. thats what i did. then enter the truck through the factory vents on the rear of the cab. i ran 2 runs "+ and -" of number 3 then reduced down to number 2 which is slightly bigger than 0AWG power wire. Number 3 is some big wire....maybe try that.

run that welding cable under the truck. thats what i did. then enter the truck through the factory vents on the rear of the cab. i ran 2 runs "+ and -" of number 3 then reduced down to number 2 which is slightly bigger than 0AWG power wire. Number 3 is some big wire....maybe try that.

I thought about that, the rear vents are noisey and I was just gonna seal one off. Then I can run my wire through it but I'm thinking I'll weld a stud to the frame the ground my rear batts to it!! I got one more question. My 260 amp mechman doesn't have a ground stud neither does my stock, what do you suggest on grounding my alts? And thanks for everyone's help!!!!!

It isn't necessary if it didn't come with a stud for grounding imo. So far, I haven't had a problem without by grounding rear batteries in the back only near the batteries. My voltage is generally the same or very close (within a few hundredths of a volt) whether you measure at the alt, underhood battery, rear batt/s, or the amp.

I keep hearing about this but I've never actually tried it so I can't say it doesn't help but the alt is already grounded. The only time I would think it would be necessary is if the alternator is not mounted to the engine block. It might be necessary for extra alts mounted on a bracket made of non-conductive material.

I think I will dig out some spare cable I have around here and try grounding the alternator itself. I will test and record results with the ground cable bolted up to different spots and see if we can get some different results. If I have a long enough length, I will do a negative run front to back and record the results from that as well. If anyone has any suggestions about where to ground the alt or any other simple wiring/voltage tests you can think of, let me know by tomorrow and I'll do my best to get test and record the results (which will be posted on soon after I get done performing the tests).I'm going to try at least a couple of different points on the engine and probably even one or two on the chassis. I will measure and record voltage at each point (alt, front batt, rear batt, amp).

Now, let's hear some ideas/suggestions.