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Still getting low voltage


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My setup is salt4k with 2 x12s. Brand x 270a alt. Xs 5100 under the hood and 3400 in the trunk. 0gauge from alt + and - straight to front battery. 0gauge everywhere else as well. At idle I’m getting 14.3-5v at my amp. Once I turn on some music at tilt I’m still dropping into the low 11’s. Made some calls and was told buy another battery… no help there. Nobody has asked if I even checked the grounds which is my first thought. I haven’t checked it yet. But since my grounds in the trunk are in a questionable spot (seatbelt bolt) I ran 2 lines from it to the back battery. Any thoughts might help before I start tearing it all apart. Also after bumping like a full song or 2 my voltage doesn’t seem to recover very well. It will raise back up to mid 13’s. After parked for a while on restart it will say back in the 14’s. Thoughts?

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There can be a lot of different culprits, but I have to agree, I don't think you have quite enough. Another battery, or upgrade to a solid lithium battery. 

The grounds are huge! If your grounds suck, adding another battery won't help at all. Running that kind of power, I recommend going to the frame and doing the big 3 upgrade. 

Also, it depends what kind of car/ what year you drive. Some cars take full control of the vehicles electrical system and can cause it to do many stupid things. All in the name of gas mileage. 

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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I’m gonna check the resistance in my ground when I get a chance. I do have the big 3ish lol. The frame is pretty much impossible to get to without a lift but I did add some wire from motor to frame close to headlights. I made sure to sand it down good. Also did the same on battery to other side. So I call  it the big 3ish. I thinking about just running a ground all the way back as well to cancel out that seatbelt bolt all together. Since I have the alternator ground straight to battery I figured a run to the back would solve any issues with the grounding. But I guess I’m gonna have to suck it up and grab a lithium. I just bought the damn xspowers as well. 
 

but on another note yes my car is pcm controlled so maybe need to bypass that as well to get full power from the alternator? Seems like it’s always something to upgrade. 

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You're not wrong dude. When you strive for perfection, you can never achieve it. 

Before you look into bypassing your PCM, look into how it specifically works. You may not need to, it may not be your problem. 

I'd be willing to put money on those seat belt bolts are not sufficient. I know it's a pain, but you have to get under there and get to the frame. It's just a way better conductor for your current to get back to where it needs to be. Gotta upgrade from the battery negative to the engine block, or alternator negative, and gotta get that alternator/ engine block ground down to the frame. 

Also, I just assumed you where, but are you using OFC cable? 

Those SALT amps are pretty efficient, but they're still beasts! They need to eat. If you can spare it, a lithium battery would definitely be the way to go. The discharge and charge rate of a lithium is far superior over any AGM. I know it's just one more thing to buy, but 1 single lithium in the back takes up way less space and costs less than 1 AGM under the hood, and 2 more in the back. 

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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Since I have a ground from the alt to battery already should I just run a ground from the battery to the frame? I only picked the seatbelt bolts because there is so much meat on them. Probably the thickest part of the car aside from actual frame. Yes I have ofc everywhere. So now I’m thinking about grabbing a cyber6k and ditching the battery in the trunk or would I keep the agm and lithium in the trunk? I could keep the agm under the hood right? Or would they fight each other? Thanks for all the help

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19 minutes ago, Scottylaw said:

Since I have a ground from the alt to battery already should I just run a ground from the battery to the frame? I only picked the seatbelt bolts because there is so much meat on them. Probably the thickest part of the car aside from actual frame. Yes I have ofc everywhere. So now I’m thinking about grabbing a cyber6k and ditching the battery in the trunk or would I keep the agm and lithium in the trunk? I could keep the agm under the hood right? Or would they fight each other? Thanks for all the help

The lithium and AGM would fight each other when the car is off, dramatically decreasing the lifespan of both batteries. I would go one or the other. I'm going to be powering 2 SALT 4's off a single Cyber 12k (I saw a guy powering a Cresendo 12k with a Mechman 370 and a single 12k) so I think a cyber 6k would do you well with that alternator. 

So, in the electrical system of your car, the start point, and the end point is your alternator. Your alternator is grounded to your engine blockthrough the bolts, so that's basically the same thing. So your grounds need to get back to the alternator as easily as possible. If there are welds in the way or anything impeding the flow of current, that's your bottleneck. Even though the piece of metal at the seat belt bolts looks thick, there could be other reasons the flow can't get where it wants to. That's why the frame is usually the best place, and why the big 3 is configured the way it is

 

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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So ditch the agm in trunk for sure but what about the one under the hood? 
im starting to miss how my old setup ran so smooth on factory power lol… this is becoming a fun hassle. 
 

after typing I thought about it and I would guess run an isolator in between the agm under the hood and the lithium in the back to keep them from fighting when the ignition is off. 

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Yeah, low power systems are a lot easier, but not as fun lol. 

If you go lithium, I would get rid of all AGM's. The only thing I'm worried about is the alternator. I was able to compare apples to apples. I would think a Cyber 6k and a 270 should be able to push the SALT 4 easily with minimal drop, but I can't be sure. I can't find any comparable videos on YouTube that are similar to your setup. I would hate to tell you to get a Cyber 6k and it not be enough. 

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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Yea check all connections maybe another run of power wire

06 Charger

Pioneer double din

Pioneer 6.5 and 6×9's

Knukoncept Krystal kable rca's

0 ga knukoncept kolossus wire 

Big 3 same wire ^ 1 run 

8g karma ss speaker wire

Sundown sia 3500d at 1ohm

2 Sundown U series 12's

Duralast platinum agm H7 (Main)

Xs power d3400

Trying to find a ho alt

 

 

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