Horrible voltage drop. What do i need to fix/upgrade?

[Joseph7195 10+ year member]

Hey man, thanks for the input! but i have done the big three including a ground running from Alt case to the frame.I had did a update in a post and found that under the hood, even with the hardest hitting songs my battery stays above 13.9 at idle. While i measured at the amp voltage i was getting 10-11v and on the same part on the same song while measuring at the battery, i was getting 13.9v-14.2v. So i dont think the probably is under the hood anymore. it has to be somewhere between the battery and the amp connection. Or the amp its self (gains or grounds) I have KNU 4 guage wire with a 80amp fuse on around a 6ft piece or wire, i dont think i should be getting that big of a drop, im only running the amp at 2 ohms....

On a side note though, i will definitely take a look at that and sand some paint off and bolt it to the frame, just for the sake of having a better ground

YOu're exactly right, you shouldn't have as much voltage drop at the amp as you are having. I would take the battery out tonight too, and let it just sit overnight. And in the morning check the voltage, you may just have a bad cell in it, and the alt is charging correctly at 14 volts, but the battery never charges all the way.

You will never go wrong upgrading your battery. I ran around 2500 watts with a Duralast 1000 amp AGM up front, and an XSTATIC 2,000 amp battery under the bak seat, and would only dip below 12 volts during a competition burp run for 30 seconds.

 

[wew lad 5,000+ posts]

you could be using too much current for that fuse yes, it's close but its definitely possible. 1000w @ 12v is 83 amps. how long is that ground wire? it might of been a better ground to run your ground directly to the truck body. the frame is generally considered a worse ground for that current, even though you have an extra wire from frame to battery. i have my taramps hd3000 grounded to mytruck body..

you can do a few tests to see what the problem is, run the amp near full tilt, and check your voltage drop referencing the amp ground set screw with the pos, fuse pos, and before the fuse to see if theres drop. you can do the same thing while changing where your ground is, on the set screw, directly on the frame, directly on the body, on a different ground location, etc.

keep in mind you have to be methodical about it.

 

[germanyt 10+ year member]

I just posted a video of drop as well. Gonna grab the voltmeter and check a few things. Will report back.

 

[los33 10+ year member]

My power wire is fairly short, around a 6ft piece iirc. The amp is only under the driver seat and the battery is against the firewall of the driver side. Im grounded to the frame. I have a 80 amp fuse on there. Even though it should be a 120 amp fuse. I have a 100 amp fuse i could try but i dont think that has anything to do with it since, the 80amp would pop over 80 not just restrict flow. I would assume 4 guage wire is fine for 800ish watts. What else can i check?

To small of a fuse or wire will drive the amp to clip. It wont pop fuses unless theres a large spike in amperage from the battery or from the amp.

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[dbjunior 10+ year member]

That short of a run I would just run a dedicated ground from amp to battery

 

[MrAcd 10+ year member]

I actually found the issue //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif i was gonna check the power before and after the fuse i noticed that on the exit of the fuse it was barely in there and it was corroded, so i fixed that and it helped a ton, lowest measurement at idle measured at the amp was 12.98v and average while cruising was around 13.5-13.7v so i figured that fixed the issue, though i looked at the fuse block before, i guess i didnt look close enough.

 

[MrAcd 10+ year member]

To small of a fuse or wire will drive the amp to clip. It wont pop fuses unless theres a large spike in amperage from the battery or from the amp.


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Oh really? can anybody else comment on this? If thats the case i will order my 120amp fuse tonight.

 

[audioholic 5,000+ posts]

The fuse size should be calculated from the maximum capacity of the wire being used, period. The wire size should be calculated from the current demands of the amplifier. If you follow those steps, you wont be playing some guessing game about your fuse restricting current.

Too small of a fuse means it will pop, not that it will add resistance to the circuit. Fuses are specifically designed to fail when their current capacity is exceeded (for a given amount of time). If the filament in the fuse is so small that it would add such a large amount of resistance to the circuit (and cause a voltage drop), it would simply burn out. That is exactly how they work, the excessive resistance on the filament heats it up to the point of failure. Fuse size will not realistically affect voltage drop, but the quality of the connections to it could.

 

[los33 10+ year member]

The fuse size should be calculated from the maximum capacity of the wire being used, period. The wire size should be calculated from the current demands of the amplifier. If you follow those steps, you wont be playing some guessing game about your fuse restricting current.
Too small of a fuse means it will pop, not that it will add resistance to the circuit. Fuses are specifically designed to fail when their current capacity is exceeded (for a given amount of time). If the filament in the fuse is so small that it would add such a large amount of resistance to the circuit (and cause a voltage drop), it would simply burn out. That is exactly how they work, the excessive resistance on the filament heats it up to the point of failure. Fuse size will not realistically affect voltage drop, but the quality of the connections to it could.

In the case of how car audio works then a fuse thats 25% smaller could easily with stand the heat/amperage of the wire especially if used mainly on music.

If a fuse is partially blown then it would create erratic voltage and/or cause damage from amperage spikes.

IF this 4 gauge wire is cca then 80 amp fuse is correct size for it.

Once a wire is being used near its maximum current capacity it induces heat which will start to drop voltage the more its used.

Using a smaller wire at its max capacity when an amplifier is still able to produce more will cause the amp to clip trying to over drive it on low power (high gain, bass boost, high rca voltage).

One main true fact tho like said a bad connection can cause many problems.

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[MrAcd 10+ year member]

In the case of how car audio works then a fuse thats 25% smaller could easily with stand the heat/amperage of the wire especially if used mainly on music.
If a fuse is partially blown then it would create erratic voltage and/or cause damage from amperage spikes.

IF this 4 gauge wire is cca then 80 amp fuse is correct size for it.

Once a wire is being used near its maximum current capacity it induces heat which will start to drop voltage the more its used.

Using a smaller wire at its max capacity when an amplifier is still able to produce more will cause the amp to clip trying to over drive it on low power (high gain, bass boost, high rca voltage).

One main true fact tho like said a bad connection can cause many problems.

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There was a bad connection but like i said its fixed, this is KNU 4 guage CCA i would almost say its over sized. I dont know wheter this damage was done already or due to the wire being only half way in one side but the holder had some melted plastic on it, and the the other side had a SUPER SMALL burnt mark on it.

 

[los33 10+ year member]

There was a bad connection but like i said its fixed, this is KNU 4 guage CCA i would almost say its over sized. I dont know wheter this damage was done already or due to the wire being only half way in one side but the holder had some melted plastic on it, and the the other side had a SUPER SMALL burnt mark on it.

When funds are good change out the holder and fuse.

Melting of any kind isnt good as you never know where it got to.

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[MrAcd 10+ year member]

When funds are good change out the holder and fuse.
Melting of any kind isnt good as you never know where it got to.

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I will most likely ordered it when i order more wire again, there was also like a split in the wire jacket from melting, like i said though it might of been caused from the loose connection or because of what we had said earlier. So go for a 120amp fuse?

 

[audioholic 5,000+ posts]

In the case of how car audio works then a fuse thats 25% smaller could easily with stand the heat/amperage of the wire especially if used mainly on music.
If a fuse is partially blown then it would create erratic voltage and/or cause damage from amperage spikes.

IF this 4 gauge wire is cca then 80 amp fuse is correct size for it.

Once a wire is being used near its maximum current capacity it induces heat which will start to drop voltage the more its used.

Using a smaller wire at its max capacity when an amplifier is still able to produce more will cause the amp to clip trying to over drive it on low power (high gain, bass boost, high rca voltage).

One main true fact tho like said a bad connection can cause many problems.

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What is a partially blown fuse? I have seen a fuse whose filament broke, but the pieces still laid together. That could add extra resistance I suppose, but not a very common problem.

 

[los33 10+ year member]

What is a partially blown fuse?

In most cases where a fuse melts and makes some kind of contact like metal on metal causing a permanent connection.

Or it melts erratically in different spots making a half melted fuse.

These things can happen on ANL fuses.

Its rare on smaller fuses with less metal.

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[Roland 10+ year member]

FUSE???

All this talk of the fuse possible being a cause is strange to me. Has any body EVER measured varying voltage drops change from different size fuses?

I've done many experiments with fuses and always found fuses to ether work, or it blows. The only time a fuse caused a a voltage drop for me was right before it would blow. Personally I have always tried to use the smallest fuse i could get away with and it has never caused any voltage drop. I change fuses till i could get a fuse to blow from playing music then use the next size or two sizes up fuse.

Op, like mentioned before, your issue is most likely wire, wire connection points, or ground.