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#### shoodidagen

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Hey all, I'm about to embark on a new build but have found issues which are getting in the way of me upgrading the Battery Negative to the Chassis (all other cable upgrading is fine).

I'm trying my best to understand DC circuits in regards to its Energy use throughout the loop from source positive to return negative.
I'm getting a lot of answers from assumptions and i feel i'm being misled!
I have spent time trying to research and do the math but i'm really not great at it.
I thought i'd ask those who understand better than i do.

I know the following is a true fact;
Larger current flow requires a larger AWG wire.

The statement in question for debate is this;
- The negative side of the DC Load can be a lower AWG than the Positive

Reasoning;

If the load is 'Converting' current into Light, Sound, Heat as i'm being told.. surely said current is spent/used during that process?
Therefore, there's little current flow coming out of the LOAD as it has been converted into other energy.
There's still a voltage of course.

Many people seem to think 'what goes out must come in' but if the current was the same going into a battery than it was coming out, the battery would never discharge, right?

Thank you for taking the time to read and i hope someone can point me in the right direction with this.
-S

#### Grinder

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Practically speaking, current is the same for both positive and negative wires. You can confirm this for yourself with a DC clamp meter. Also, current-measuring shunts are commonly placed on the negative wire. Ampacity (determined by conductor material, gauge, length and insulator material heat rating) of both positive and negative wires needs to be the same.

#### shoodidagen

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Discussion Starter · ·
Practically speaking, current is the same for both positive and negative wires. You can confirm this for yourself with a DC clamp meter. Also, current-measuring shunts are commonly placed on the negative wire. Ampacity (determined by conductor material, gauge, length and insulator material heat rating) of both positive and negative wires needs to be the same.

Thank you for your time. This makes sense to me and i'm going to build a few circuits to test some theorys out.
Am I perhaps getting 'current' mixed up with 'electron charge' here?
Would a highly charged electron need the same amount of conductor material as one that has had most of its 'charge' used up?

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bbfoto

#### FAUEE

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Before we get dragged down in theory too much here, what is it you're wanting to do, and why?

Can you use a lower awg wire for your ground? Absolutely, it's a larger wire so you can and have basically no ill effects. But if you were to use a higher awg wire for your ground, you'd be increasing the resistance of your ground which has all kinds of negative effects.

#### Grinder

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Before we get dragged down in theory too much here, what is it you're wanting to do, and why?

Can you use a lower awg wire for your ground? Absolutely, it's a larger wire so you can and have basically no ill effects. But if you were to use a higher awg wire for your ground, you'd be increasing the resistance of your ground which has all kinds of negative effects.
Good point. Our use/misuse of terminology can lead to confusion.

Based on the OP's statement (and later "reasoning"), "I know the following is a true fact: Larger current flow requires a larger AWG wire." I assume the OP means larger diameter, rather than larger numerical AWG.

FAUEE

#### Holmz

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7,703 Posts
Thank you for your time. This makes sense to me and i'm going to build a few circuits to test some theorys out.

Am I perhaps getting 'current' mixed up with 'electron charge' here?
I suspect at least ^that^, and maybe more.

Would a highly charged electron need the same amount of conductor material as one that has had most of its 'charge' used up?
The charge of an election is a constant, like the gravitation constant, or planks constant, or the speed of light..

If the electrons were not flowing then they would end up piled up somewhere like ball lightning.
Or those subatomic particles disappearing?

You are likely mixing up the concept of current, with the concept of voltage.
The voltage usually drops along the way, but not the current.

#### ckirocz28

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4,319 Posts
Hey all, I'm about to embark on a new build but have found issues which are getting in the way of me upgrading the Battery Negative to the Chassis (all other cable upgrading is fine).

I'm trying my best to understand DC circuits in regards to its Energy use throughout the loop from source positive to return negative.
I'm getting a lot of answers from assumptions and i feel i'm being misled!
I have spent time trying to research and do the math but i'm really not great at it.
I thought i'd ask those who understand better than i do.

I know the following is a true fact;
Larger current flow requires a larger AWG wire.

The statement in question for debate is this;
- The negative side of the DC Load can be a lower AWG than the Positive

Reasoning;

If the load is 'Converting' current into Light, Sound, Heat as i'm being told.. surely said current is spent/used during that process?
Therefore, there's little current flow coming out of the LOAD as it has been converted into other energy.
There's still a voltage of course.

Many people seem to think 'what goes out must come in' but if the current was the same going into a battery than it was coming out, the battery would never discharge, right?

Thank you for taking the time to read and i hope someone can point me in the right direction with this.
-S
Everyone missed the obvious, electrons are negatively charged and "move" from the negative terminal to the positive terminal. So, you need that big ground wire. You can add extra grounds between the engine and chassis, and you should even if you can't upgrade the negative battery cable.
What exactly is the problem anyway? Maybe we can help.

#### 156546

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You can use a smaller gauge of wire for the ground--usually--because the wire is often a lot shorter.

#### JohnnyOhh

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how much current will you be drawing and what size wires are you debating/thinking about using?

#### mrexcitement

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Ground wire AWG has to be the same as the positive wire AWG , it's a complete circuit which means the current flows through both cables equally so needs to be the same AWG.

You could possibly reduce the ground AWG if it's very short but I wouldn't , it's not worth it and keep the ground wiring the same.

As far as size goes it all depends on how much voltage drop you are willing to accept , for me I always want the minimum voltage drop across the cables which requires the largest AWG I can fit/afford.

For my 2 x 1200WRMS amps this requires 0 gauge from the battery to the distribution block which then splits into 2 x 4 gauge short cables for each amp , the ground on the battery to chassis is 0 gauge and also the 2 x 4 gauge grounds from the amps go to a joining block then a single 0 gauge to the chassis.

#### Thomasluke7899

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In a car resistance is what matters. Like already stated the ground wire can be a smaller size wire. The reason being is the resistance. It doesn't matter how big or how small the wire is.
It pretty simple. As the wire heats up the resistance goes up. Which makes the wire temperature go up. Which makes the resistance go up. See where this is headed?
Everything is fine up until the point at which the ground wire are any part or the closed circuit but we are just talking about the ground.
So for example if you have a 4 awg power wire and are pulling 50 amps you could theoretically use a 10awg wire as long as the wire is like 2 or 3 foot long and the circuit doesn't have more than 50 amps flowing through it your good.
But...as you go over 50 amps of currents that 10 awg wire begins to heat up.
60 amps hotter. Time also causes heat build up do to the fact the wire has no way to dissipate the heat.
So after a certain amount of time with a certain amount of current the 10awg wire will fail.
That will continue to happen until the ground wire has the same or close to the same resistance.
This is true for any part of the circuit.
Thats why fuses work so well. They burn through under a calculated amount of time and heat.
So you we have fast blow fuses. Slow blow fuses. Ect....

#### bbfoto

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You can use a smaller gauge of wire for the ground--usually--because the wire is often a lot shorter.
Dude! While true, decent Tinned OFC power & ground wire ain't all that expensive in the scheme of things. IME, it's a negligible cost compared to the overall installation, so why skimp?

OP, check out the cost/quality/performance power wire comparison videos on the HifiVega YouTube channel.

90% of the "system", or "amplifier", or "noise" issues we see in the install bay are due to poor ground (or power) connections, or insufficient wire gauge for the required current demand.

And many modern vehicles have a horrible ground plane due to the body & structural panels being "glued" together instead of welded, riveted, or other metal fasteners being used.

Maybe the OP is installing his system into a fiberglass/composite Corvette or a late model Aluminum body Ford F-150, which BOTH require Power AND Ground runs directly to the battery terminals (with proper fusing, of course).

OP: DC power circuits are a "continuous loop" or a "Round Trip" type of circuit of electron flow. Think of them as an oval race track with the power source and the power consumption device(s) being wired in series along the oval track. And all of the race cars (electrons) continuously travel in only one direction.

Any resistance to a given voltage and current supply or demand in the wiring, or through the vehicle's ground plane/body (and on either the Negative or Positive side) will be a bottleneck "in the track".

If the oval track becomes narrow at any point, only a single race car might be able drive through that section of the track at any given time, instead of multiple race cars being able to run side by side.

Perhaps a poor analogy, but that's all I got.

There are many car audio power wire calculators on manufacturer's websites...Rockford-Fosgate, Kicker, JL Audio, etc.

And though the website is dated, an excellent resource is

www.bcae1.com

#### jheat2500

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2020 Ram 2500 Mega Cab
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232 Posts
Hey all, I'm about to embark on a new build but have found issues which are getting in the way of me upgrading the Battery Negative to the Chassis (all other cable upgrading is fine).

I'm trying my best to understand DC circuits in regards to its Energy use throughout the loop from source positive to return negative.
I'm getting a lot of answers from assumptions and i feel i'm being misled!
I have spent time trying to research and do the math but i'm really not great at it.
I thought i'd ask those who understand better than i do.

I know the following is a true fact;
Larger current flow requires a larger AWG wire.

The statement in question for debate is this;
- The negative side of the DC Load can be a lower AWG than the Positive

Reasoning;

If the load is 'Converting' current into Light, Sound, Heat as i'm being told.. surely said current is spent/used during that process?
Therefore, there's little current flow coming out of the LOAD as it has been converted into other energy.
There's still a voltage of course.

Many people seem to think 'what goes out must come in' but if the current was the same going into a battery than it was coming out, the battery would never discharge, right?

Thank you for taking the time to read and i hope someone can point me in the right direction with this.
-S
What exactly do you mean by "upgrading" the battery's negative cable? Are you trying to replace it? Can you provide more specifics as to what you're trying to accomplish and what is preventing you from doing so?

#### jheat2500

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232 Posts
Dude! While true, decent Tinned OFC power & ground wire ain't all that expensive in the scheme of things. IME, it's a negligible cost compared to the overall installation, so why skimp?

90% of the "system", or "amplifier", or "noise" issues we see in the install bay are due to poor ground (or power) connections, or insufficient wire gauge for the required current demand.

And many modern vehicles have a horrible ground plane due to the body & structural panels being "glued" together instead of welded, riveted, or other metal fasteners being used.

Maybe the OP is installing his system into a fiberglass/composite Corvette or a late model Aluminum body Ford F-150, which BOTH require Power AND Ground runs directly to the battery terminals (with proper fusing, of course).

OP: DC power circuits are a "continuous loop" or a "Round Trip" type of circuit and electron flow. Think of them as an oval race track with the power source and the power consumption device(s) being wired in series to the oval track.

Any resistance to a given voltage and current supply or demand in the wiring, or through the vehicle's ground plane/body (and on either the Negative or Positive side) will be a bottleneck.
I think you may have missed the reasoning behind the OP's question, and subsequently, the context of Andy's response. OP doesn't appear to be "skimping", he/she is trying to work around an apparent road block.

#### bbfoto

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I think you may have missed the reasoning behind the OP's question, and subsequently, the context of Andy's response. OP doesn't appear to be "skimping", he/she is trying to work around an apparent road block.
Yeah, more detail regarding the specific vehicle, what the specific limitations are, the audio system's power requirements, and what problem he is trying to solve would be helpful.

Most likely something to do with trying to bypass/circumvent the OEM ECM's ammeter sensor on the negative battery terminal/ground wire.

#### Holmz

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7,703 Posts
I think you may have missed the reasoning behind the OP's question, …
What reasoning?

?This?:

Thank you for your time. This makes sense to me and i'm going to build a few circuits to test some theorys out.
Am I perhaps getting 'current' mixed up with 'electron charge' here?
Would a highly charged electron need the same amount of conductor material as one that has had most of its 'charge' used up?

#### dumdum

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4,515 Posts
Just use the same size for both, shorter runs can be smaller, but you don’t reduce current flow after a load, it’s the exact same, you don’t offload some current, that’s not how it works

If your amp draws 100a there will be 100a from battery to amp and 100a from amp to battery whichever path it has to take

for the sake of a 12” piece of cable or whatever just use the same

funny story, the Finnish guys got laughed at in db drag with 3kw amps with four awg power and earth… they were clever cookies and had 12” runs from batterys to amps, they didn’t need any bigger for such short runs even with 250a per run and set multiple world records

cable needs to be big enough for the current flowing and the length, I’d always go the same size for power and earth regardless though, it’s so cheap for short lengths why wouldn’t you?

#### haakono

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Maybe the OP is installing his system into a fiberglass/composite Corvette or a late model Aluminum body Ford F-150, which BOTH require Power AND Ground runs directly to the battery terminals (with proper fusing, of course).
Why does the F150 require that?

#### Grinder

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Why does the F150 require that?
Galvanic/dissimilar-metal corrosion (e.g. steel fastener-to-aluminum), and/or bonded chassis/body panels, I presume.

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