Ground connection

[icedbimmer 10+ year member]

Is it ok to hook up the ground cable of an amp to the negative terminal of your battery?

My brother took his car to Circuit City and that is what they did? We both have BMW's which have the battery in the trunk, but I hooked up my ground wire to the chassis.

Thanks.

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[chris229 10+ year member]

ALWAY connect to the chassis. Don't run the wire back to the battery as you will be adding resistance due to the added wire.

 

[jlaine 10+ year member]

Originally posted by icedbimmer Is it ok to hook up the ground cable of an amp to the negative terminal of your battery?

My brother took his car to Circuit City and that is what they did? We both have BMW's which have the battery in the trunk, but I hooked up my ground wire to the chassis.

Thanks.

Sounds like circus city decided to get more $$ out of you. Unless you are running on a galvanized/fiberglass body, you don't need to do that...

Your installation procedure is fine... theirs was just added time really...

 

[bootleg 10+ year member]

Yeah, I think you got fuucked by Circutous City. Personaly I would never allow any of my freinds or family get there stuff installed there.

 

[more_spl 10+ year member]

his battery is in the trunk. i heard the negative side is as good or better than a chassis gorund. and since it's already close enough (in the trunk) why not?

 

[jlaine 10+ year member]

Originally posted by more_spl his battery is in the trunk. i heard the negative side is as good or better than a chassis gorund. and since it's already close enough (in the trunk) why not?

I missed that portion...

If the battery is in the trunk, hell, I'd connect it straight to it.. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[icedbimmer 10+ year member]

I guess it's OK then. Thanks.

 

[chris229 10+ year member]

guys the car body will conduct current better at ANY length over wire. The car body is the biggest gauge wire you can get. This will cause LESS voltage drop than ANY gauge wire your going to use.

 

[Billyf17 10+ year member]

So Chris you're saying that running a yard of ground wire to the chassis, which the current has to find the negative terminal on its own, is better than running 6 inches of wire to the terminal?

 

[blackgeltabs 5,000+ posts]

Chris im sorry but your wrong. You see in a perfect world that might just possibly be true. But there things like rust and corrosion that can get in the way. You see all ground has to go back to the battery anyways, your car sitts on 4 rubber tires, thats why they say cars are safe in lightning storms. The way circuit city did it is great becasue you have the battery in the trunk. A couple of my automotive teachers have asked "why dont you run a ground wire straight to the battery for all of your amp thingies, instead of grounding them to the rusted a$$ body" Iv been wanting to try this and poke around with the volt meter just to see where it would get me. Running the ground wire to the battery would truly be completeting the circuit in electrical theory.

 

[chris229 10+ year member]

Originally posted by blackgeltabs Chris im sorry but your wrong.

sure I am

You see in a perfect world that might just possibly be true. But there things like rust and corrosion that can get in the way

you clean ALL connections no matter if they are rusted or not. solves that problem.

You see all ground has to go back to the battery anyways, your car sitts on 4 rubber tires, thats why they say cars are safe in lightning storms.

no one was ever saying that the ground is an earth type

The way circuit city did it is great becasue you have the battery in the trunk.

no it really isn't and that is way they are circuit city installers

A couple of my automotive teachers have asked "why dont you run a ground wire straight to the battery for all of your amp thingies, instead of grounding them to the rusted a$$ body"

first if they knew anything about automotive electronic they would know ALL circuit use the body as a ground. Runing back to the battery is a waste of time AND would cause more resistance. Ask your physics teacher about electrical theory NOT the auto tec guy. The auto tec guy should know that no one is intending a rusted connection. This would defeat the purpose of trying to eliminate resistance.

I'v been wanting to try this and poke around with the volt meter just to see where it would get me.

yea try it and post back

Running the ground wire to the battery would truly be completeting the circuit in electrical theory.

well either way is completing the circuit. If you don't understand that then you cann't possibly understand THIS thread. The point is to eliminate resistance.

 

[Billyf17 10+ year member]

Dude you're making this harder than it is. I don't care about your petty little explanations but you in this instance are not correct. It would lose less voltage if you run straight to the battery in this case. Like I said a foot of pathway is a lot better than a navagating to the negative lead in the body.

Just quit while you're a head.

 

[jlaine 10+ year member]

Originally posted by chris229 guys the car body will conduct current better at ANY length over wire. The car body is the biggest gauge wire you can get. This will cause LESS voltage drop than ANY gauge wire your going to use.

Sorry, but the battery is an arms length away, so explain why it would be better than:

1. Jumping off the battery to a connection to the chassis.

2. Running through the chassis to the other side of the vehicle.

3. Jumping off the chassis onto whatever pickup point you've isolated.

4. Running to the amp.

OR....

Direct connect to the battery.

Cleaning connections will not prevent future oxidation. Ask any EE, what they'd prefer.

7 feet of travel path with two resistant prone junctions, or 5 feet of travel path, with a direct connection.

No brainer.

The voltage drop across such a miniscule lead is pathetic and is going to be impossible to read under normal circumstances. (Read, proper gauge wire installed). In this case, CC did the wise thing.

The vehicle chassis loses this battle, because the battery is in the back already. Sorry...

 

[blackgeltabs 5,000+ posts]

quote:

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You see in a perfect world that might just possibly be true. But there things like rust and corrosion that can get in the way

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you clean ALL connections no matter if they are rusted or not. solves that problem.

No No, I mean rust spots through out the body of the car and in the under carriage, they create resistance when the current is on its travel path to the battery.

quote:

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You see all ground has to go back to the battery anyways, your car sitts on 4 rubber tires, thats why they say cars are safe in lightning storms.

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no one was ever saying that the ground is an earth type

No but I am saying that it travels back to the battery, therefore haveing the battery in the trunk would BE to YOUR ADVANTAGE.

quote:

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A couple of my automotive teachers have asked "why dont you run a ground wire straight to the battery for all of your amp thingies, instead of grounding them to the rusted a$$ body"

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first if they knew anything about automotive electronic they would know ALL circuit use the body as a ground. Runing back to the battery is a waste of time AND would cause more resistance. Ask your physics teacher about electrical theory NOT the auto tec guy. The auto tec guy should know that no one is intending a rusted connection. This would defeat the purpose of trying to eliminate resistance.

See this is where I really had to laugh, You see my teachers are not idiot mechanics. Infact they are quite intelligent and they do know what they are talking about. Especailly when It comes to autoelec. But you see your comment about the circuits, most car circuits are 5volts NOT 1400+ watts.

This is just getting to a point where its completely off topic.

 

[nismboy6986 10+ year member]

chris no disrespect but you are soundling like the type of expert that can't admit they are wrong. normally it would be better to connect it to the chassis than directly to the battery because techincally you are using a line that would be about -100 gauge in size compared to 0 gauge which would mean less resistance. but in a bmw the battery is in the back so their isn't any real voltage loss using a direct connection since the direct connection is shorter than the chassis connection. The situation is kind of like you are saying its better to take the 4 lane highway to a place because the traffic is less congested than the 2 lane. But its a 10 mile trip with 2 lane compared to 50 miles with the 4 lane so the distance from point A to point B is shorter using the 2 lane so you will get to the place quicker on the 2 lane with less aggrivation (resistance) because you don't have to get off exits and what not (traveling through the whole chassis)