# Made and installed my own "big3" today.



## Gnfanatic (Oct 2, 2013)

Since tecollins1 took my $90 3 months ago and disappeared I decided to make my own so I can get my stereo running. I used high quality OFC , high flexibility 1/0 AWG copper wire. I also bought military grade battery terminals and removed the oem pieces. I did it differently compared to some of the guys on here. Everything was crimped, soldered and tested with my fluke meter. I am happy how it came out. Any comments are welcomed.


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## XtremeRevolution (Jan 19, 2012)

I'll have to contact him to give you a refund. PM me your info. I talked to him not long ago and he said he'll give me the dimensions for the design so I can start making them instead.


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## trevor_geiger (Nov 29, 2012)

XtremeRevolution said:


> I'll have to contact him to give you a refund. PM me your info. I talked to him not long ago and he said he'll give me the dimensions for the design so I can start making them instead.


What wire brand are you going with? Knu or Sky High or what else? I might be interested in a 1/0 kit when I see you.


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## Gnfanatic (Oct 2, 2013)

Hhmmmm. My battery saver went active and dont know why. The battery idiot light did not go on. I am getting 15.3 volts at idle and after 4 hours parked the voltage is 12.76. Nothing funky like dimm lights is going on either.


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## Gnfanatic (Oct 2, 2013)

Andrei, any comments on this?? What I found strange was when I removed the neg battery terminal sparks were flying off of it like there was current coming out of it. Never seen that before on a grd cable.


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## XtremeRevolution (Jan 19, 2012)

Did you remove any of the stock wiring?


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## Gnfanatic (Oct 2, 2013)

If you look at my pics. I removed the stock pos wire's and replaced them with my own. I also re-located the stock little grd wire and attached it to the firewall/


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## Blue Angel (Feb 18, 2011)

Gnfanatic said:


> View attachment 111314


The only thing that sticks out to me is that only one of your ground wires is going through the hall-effect sensor (ring shaped sensor on the battery tray). The BCM will think only see half the current being drawn from the battery.

That likely has nothing to do with what you're reporting. Do you have an amp that's not turning off?


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## Gnfanatic (Oct 2, 2013)

Thanks for the reply. I dont have any amps connected as of yet. And the error message comes on when I am driving for about 15 miles on the highway. Nothing is draining the battery. Interesting what you said about the hall-effect sensor. But if only one wire was in there from the fac then mine should be fine as well, no? Dont forget, at idle I am pushing 15.2 volts. when off it is 12.72 roughly and holds it for hours.




Blue Angel said:


> The only thing that sticks out to me is that only one of your ground wires is going through the hall-effect sensor (ring shaped sensor on the battery tray). The BCM will think only see half the current being drawn from the battery.
> 
> That likely has nothing to do with what you're reporting. Do you have an amp that's not turning off?


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## XtremeRevolution (Jan 19, 2012)

Put your stock wiring back on and use the extra wiring as reinforcement. Run the stock ground wire through that sensor loop and don't run anything else through it.


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## Gnfanatic (Oct 2, 2013)

just doesnt make sense why I need to put fac grd wire back. I am going to try something tomorrow and update you guys


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## Merc6 (Jun 8, 2013)

Ground is sensitive on cars electronics. IIRC didn't someone on the FB group have this same issue on their custom Big 3 but it never returned?


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## Blue Angel (Feb 18, 2011)

Gnfanatic said:


> But if only one wire was in there from the fac then mine should be fine as well, no?


IIRC, the OEM wiring has only one battery-to-ground cable, and it passes through the sensor.

The BCM monitors the current in that ground wire to know how much current is being pulled from, or supplied to, the battery at any given time. If you run two equal gauge ground wires from the battery and only one of them passes through the sensor, the BCM will see only half of the battery load.

Like I said, I have absolutely no idea if that is related to your issue or not, just an observation. 

My personal approach to fortifying the battery ground would be to completely replace the OE ground wire with a single thicker wire and run it through the sensor. I would do so just in case doing it another way would negatively impact the BCM's battery management strategy which, from the little I know about it, is fairly advanced.


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## Gnfanatic (Oct 2, 2013)

Thanks guys, going to try something and get back to you.


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## Gnfanatic (Oct 2, 2013)

well guys, its amazing how complex cars are getting these days and how sensitive they are. When I first did the big 3 (block grd going to batt terminal) I realized not only I was getting the "battery saver active" warning but my idle (warm and in D) was 1100 rpm's. The first day I did not notice it right away because the car is quiet. Soo, thank's to you guys I removed the engine grd from batt terminal and re-located it to the fac rad support grd location. My idle went down to 700 rpms and after 30 miles NO "battery saver active" message appeared. It's amazing that the **** bcm detected this considering they all eventually go to the same location. I want to thank all of you for helping me out on this!!!


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## Blue Angel (Feb 18, 2011)

Nice! Thanks for the detailed update!

This is the first time I've read that this actually caused an issue. Just to make sure I've got your setup right, the ground wire that goes through the sensor is attached to the factory ground behind the headlight, and you had the engine ground attached directly to the battery negative terminal, right?

If so, your setup was a little different than the typical Big3, which usually just adds another ground in parallel with the factory battery ground. It DOES show that the BCM is very sensitive to what's being reported by that sensor.


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## Gnfanatic (Oct 2, 2013)

correct, that was my orig design. Now the engine block grd goes to rad support.



Blue Angel said:


> Nice! Thanks for the detailed update!
> 
> This is the first time I've read that this actually caused an issue. Just to make sure I've got your setup right, the ground wire that goes through the sensor is attached to the factory ground behind the headlight, and you had the engine ground attached directly to the battery negative terminal, right?
> 
> If so, your setup was a little different than the typical Big3, which usually just adds another ground in parallel with the factory battery ground. It DOES show that the BCM is very sensitive to what's being reported by that sensor.


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## Blue Angel (Feb 18, 2011)

Gnfanatic said:


> Dont forget, at idle I am pushing 15.2 volts.


Another thought just passed through my pea-brain.

Have you re-checked your idle voltage since putting the engine ground back to the rad support? Hav ethey changed at all?

The reasdon I ask is 15.2V sounds high to me, though I haven't checked my own voltage to see if the same thing happens with stock wiring. The hall effect sensor measures current supplied TO the battery as well as current draining from it. If the BCM is trying to achieve a certain charging load to the battery and part of the load is being supplied through another ground, it may increase the voltage to unusual levels in order to hit that target charge load.

The next time I drive my car I'll check the voltages and see what they report. Under what conditions were you checking your idle voltage? After driving for a while or just after starting? Voltage after starting is higher for a while to replenish the battery after cranking the engine, then returns to 13.X (IIRC) while driving. At night with the headlights on it is higher, around 14.4.


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## hificruzer226 (Mar 27, 2013)

I would check your resistance to ground a ton of times what happens you produce a resistance that gets picked up by the bcm which wakes it up and checks circuits . Make sure all your ground bolts are tights.


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## Gnfanatic (Oct 2, 2013)

Funny you asked, forgot to mention. The first installation the bcm kept my idle at 1100 rpms and my voltage was 15.2. Now the idle is 700 rpm's and my voltage is 14.65 to 14.70. 



Blue Angel said:


> Another thought just passed through my pea-brain.
> 
> Have you re-checked your idle voltage since putting the engine ground back to the rad support? Hav ethey changed at all?
> 
> ...


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## Gnfanatic (Oct 2, 2013)

Well everything has resistance (obviously) what is a acceptable range??



hificruzer226 said:


> I would check your resistance to ground a ton of times what happens you produce a resistance that gets picked up by the bcm which wakes it up and checks circuits . Make sure all your ground bolts are tights.


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## Blue Angel (Feb 18, 2011)

Gnfanatic said:


> Funny you asked, forgot to mention. The first installation the bcm kept my idle at 1100 rpms and my voltage was 15.2. Now the idle is 700 rpm's and my voltage is 14.65 to 14.70.


I'm on a roll! Too bad I didn't do this well playing poker tonight... maybe I should stick to cars.


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## XtremeRevolution (Jan 19, 2012)

To note, I have seen voltage go up to 15.2 even stock. It will vary from 12.4V to 15.2V. I should check to see where I'm running my ground through.


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## hificruzer226 (Mar 27, 2013)

less than 1 ohm def. it should next 0 I will reground anything that is .1 or more, make sure the surface is clean from paint grease etc


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## spacedout (Dec 7, 2010)

XtremeRevolution said:


> To note, I have seen voltage go up to 15.2 even stock. It will vary from 12.4V to 15.2V. I should check to see where I'm running my ground through.


Slightly off topic but possibly related. Before last fall I noticed my car was constantly charging at 15V or more always, no longer going to a lower 12.5-12.7V range ever. I replaced my battery with a Die Hard advanced gold AGM battery(group 47), but while doing so found the ground by the headlight loose. 

With the new battery right away my car was only charging at 12.7V idling, and as it sees fit will go to low charge mode while driving again too. After reading these posts I wonder if my issue was that loose ground & not a sign of battery starting to get weak. 

I did not core swap the AC Delco battery but installed on a 1950 Case VAC(previously converted from 6V to 12V), even after sitting all winter it started that 2.0L 4 cylinder engine just fine. So obviously there was nothing wrong with my original battery.


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## Gnfanatic (Oct 2, 2013)

I checked my for loose connection and also made sure there was no paint from the fac. all good on my end.



spacedout said:


> Slightly off topic but possibly related. Before last fall I noticed my car was constantly charging at 15V or more always, no longer going to a lower 12.5-12.7V range ever. I replaced my battery with a Die Hard advanced gold AGM battery(group 47), but while doing so found the ground by the headlight loose.
> 
> With the new battery right away my car was only charging at 12.7V idling, and as it sees fit will go to low charge mode while driving again too. After reading these posts I wonder if my issue was that loose ground & not a sign of battery starting to get weak.
> 
> I did not core swap the AC Delco battery but installed on a 1950 Case VAC(previously converted from 6V to 12V), even after sitting all winter it started that 2.0L 4 cylinder engine just fine. So obviously there was nothing wrong with my original battery.


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