2016 gmc sierra low charge voltage fixed

psyfertech · February 24, 2020

Wanted to post this because i was unable to find anyone else that figured this out first off i will explain the issue i had.

I just completed my stereo system which is 4 sundown 8's under the rear seat with a hifonics brutus running 1600w rms at 1ohm, for mids and highs all deaf bonce door speakers with crescendo f1 tweets in the dash all running on a skar 150.4 amp as well as a audio control EQS sound processor. I also used a pac audio amp pro to get my rca pre outs from the factory can bus and retained the stock head unit and one nice feature of it was being able to adjust door chime volume. After all of this as you can imagine the elctrical draw is quite a bit more and even with the big3 and all o guage wiring i was getting voltage drop so my plan was to first add a second battery and then maybe a better alt if i had to.

So i bought a XS power D5100 battery and installed it on the driver side battery tray with my own customized mounting hardware, i ran a 0 guage across the firewall and linked both batteries with a 300amp fuse in between and for my ground i went straight to the frame on the driver side and hooked my amp to the new battery.

About a day or so later i found that my charge voltage dropped way low and i was seriously concerned and honestly thought my alternator took a dump, what it would do is when the truck was first cranked it would start out charging at 14.6 then steadily drop down to about 11.8 to 12 and would just sit there unless i turned my headlights on, with the headlights on it would sit around 13.8. I did as much googling as i could and i ended up finding out about gm (RVC) regulated voltage control, basically there is a little metering clamp on the ground wire coming off of your battery it is tied in to the trucks computer and it monitors the current draw and then tells the alternator how much juice it needs. Its debatable whether its sole purpose is for fuel efficiency or for extending battery life either way theyve had this system in place since 2005 from what ive read and it works, it works well and you honestly should not have any issues with it, you may see your voltage bounce around a tad bit here and there which is normal as everyone will tell you. HOWEVER when you add a second battery as i did or when you do the big 3 as i did and you add any additional grounds in to the system you are creating a path that allows current to bypass the metering clamp and this is where you start having trouble like me and your truck is basically telling your alternator to turn off... So i created a little wiring diagram for you folks out there that want to add a second battery or beef up your grounds, as you will see this basically creates a bottle neck for all of your grounds and unfortunately the sad reality is you can only put a cable as big as that little metering clamp will allow which honestly its fairly decent i think you could squeeze a 2/0 in there, i currently just have a 0 guage ran through it feeding all my grounds and my system is working great, ever since i did this my voltage holds pretty steady when im at idle it sits around 14.4 and when my bass is at full blast the lowest it will drop to is about 13.5 to 13.8, it would seem that in my case a dual battery with the factory alternator is plenty but i know some of you bass heads out there will definitely need more juice and luckily there are plenty of options for bigger alternators for these trucks, hopefully this helps someone thats freaking out like i was when my voltage took a dump after just adding a very expensive dual battery setup lol

enjoy

Snowcamo · February 24, 2020

Its interesting that some have issues and others not. I have my second batt ground going to the frame at the bed and upgraded the start batt power and grounds.. I have zero issues charging on the stock alt. Im running 1k watts myself. Xs3100 as a second batt.

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psyfertech · February 24, 2020

8 minutes ago, Snowcamo said:

Its interesting that some have issues and others not. I have my second batt ground going to the frame at the bed and upgraded the start batt power and grounds.. I have zero issues charging on the stock alt. Im running 1k watts myself. Xs3100 as a second batt.

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Yea that is very odd maybe it has to do with the placement of the ground on the frame or something when I did my battery since it was in the spare battery tray I loterallt went straight down by the wind shield washer tank and found a frame ground that was already there and used it but either way atleast this will hopefully help.someone out one day lol I'm so glad I was able to fix mine so far it's been several days since I did it and my voltage stays right around 14 to 14.4 14.6

And hell yea u got some bump too

Yea these xs batteries are great arent they?

Edited February 24, 2020 by psyfertech

Snowcamo · February 24, 2020

Yea that is very odd maybe it has to do with the placement of the ground on the frame or something when I did my battery since it was in the spare battery tray I loterallt went straight down by the wind shield washer tank and found a frame ground that was already there and used it but either way atleast this will hopefully help.someone out one day lol I'm so glad I was able to fix mine so far it's been several days since I did it and my voltage stays right around 14 to 14.4 14.6
And hell yea u got some bump too
Yea these xs batteries are great arent they?

Yessir trunk goes bang [emoji38]... Xs or northstar here all day. No real need to upgrade the stock alt on my end.
Idk if you knew the bcm and pcm control the voltage you see on the dash. 12v isnt an issue as the computers command it to be so given a number of variables. Theres like 7 diff charging modes. That being said ive seen 12v once since my upgrade. Still no light dimming what so ever. [emoji106]

If your running the stock stereo plug in the aux cord and take a listen. You'll notice more bass off the bat lol. Youtube does flex wonders lmao! Check out XCLSV they rebass some songs[emoji817]

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psyfertech · February 24, 2020

11 minutes ago, Snowcamo said:

Yessir trunk goes bang ... Xs or northstar here all day. No real need to upgrade the stock alt on my end.
Idk if you knew the bcm and pcm control the voltage you see on the dash. 12v isnt an issue as the computers command it to be so given a number of variables. Theres like 7 diff charging modes. That being said ive seen 12v once since my upgrade. Still no light dimming what so ever.

If your running the stock stereo plug in the aux cord and take a listen. You'll notice more bass off the bat lol. Youtube does flex wonders lmao! Check out XCLSV they rebass some songs

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Yea I think my alt is good to seems to power my setup pretty well and hell yea that's nice urs is holding good voltage and same here no headlight dimming well mine came with hids so they probably wouldn't anyway lol but yea I use bluetooth and I notice when I put my flash drive in I definitely have to turn it up a bit more to get the same volume level out of it but I havent tried the aux I'll have to try it out lol and cool I'll check out those rebassed songs i found clip city recently looks like they're all from 2017 but still some clean bass

Snowcamo · February 24, 2020

Yup thank me later lol. You'll be like damn!
Disclaimer: i am not responsible for broken glass due to bass notes below 50hz lmao.

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psyfertech · February 24, 2020

6 minutes ago, Snowcamo said:

Yup thank me later lol. You'll be like damn!
Disclaimer: i am not responsible for broken glass due to bass notes below 50hz lmao.

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Hahaa hell yea man I love me some bass anything near 32hz that's my shit lol I got.my box tuned there so it hits so smoooooth

Snowcamo · February 24, 2020

Heck ya man likewise. I'm thinking of building another down firing rear console box. This time slot ported tuned to 34hz. My phone has a 16 band eq also. Might see if yours has one.

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ripinlip · February 24, 2020

@psyfertech , @Snowcamo was kind enough to share this post with me and its basically like for like what has been going on with my setup . I don't have the grounds connected and i think this is apart of the issue (the other being using a POS relay which i have the PAC coming over via amazon now)

2 quick questions for you

Before connecting your grounds on the batteries, Did you also notice static from time to time in your stock speakers?
Why did you link the 2 batteries instead of doing something like a PAC 200 to switch between them?

psyfertech · February 25, 2020

29 minutes ago, ripinlip said:

@psyfertech , @Snowcamo was kind enough to share this post with me and its basically like for like what has been going on with my setup . I don't have the grounds connected and i think this is apart of the issue (the other being using a POS relay which i have the PAC coming over via amazon now)

2 quick questions for you

Before connecting your grounds on the batteries, Did you also notice static from time to time in your stock speakers?

Why did you link the 2 batteries instead of doing something like a PAC 200 to switch between them?

Hope it helps with your situation man and holy.crap your diagram looks almost identical to how my truck is actually wired minus the battery isolator lol I'll show you pics and honestly I figured I would try it without a battery isolator first and see how it goes I guess it's probably good to have one to keep them from drawing off one another when truck is shut off I'll keep that model in mind for sure

And to answer the other question no I havent noticed any static in my stock speakers that i can remember only thing i get is some slight amp hiss and whine from the alt since I ran my power feed on the interior like a dummy definitely going to.route it under the truck when I get some more ofc cable its gotta be changed anyway I used cheap copper clad

But yea man it's totally fine to connect your grounds to the frame but you have to make sure that you wire it in such a way like I did so that the clamp is able to read all of the current if there is a ground path that bypasses the clamp u will likely get the voltage fluctuation issues