Someone help me understand this debate.

Post by **Bfowler** » Thu Mar 08, 2007 1:26 pm

the local "mr know it all" is trying to sell everyone that grounding to the battery is wrong.....

http://forums.bimmerforums.com/forum/sh ... p?t=700009

edit - btw the "debate" starts at post 7

and get more underway around post 20.

Mackenzie · Post by **Mackenzie** » Thu Mar 08, 2007 1:40 pm

Its a bmw forum what did you expect...

Post by **Bfowler** » Thu Mar 08, 2007 1:49 pm

psh whateva

Post by **Francious70** » Thu Mar 08, 2007 2:02 pm

Well, since a car is a closed circuit the best grounding point is the one of lest resistance, AKA the battery.

Unless you can magically make steel less resistive than copper, lead, and a battery.

*EDIT* You REALLY need to get ride of the body skirts mang. And who's X-kalade is that in the background?

Post by **VW337** » Thu Mar 08, 2007 2:03 pm

Third bullet point from the end............

http://phoenixphorum.com/trouble-shooti ... vt178.html

Capital_M · Post by **Capital_M** » Thu Mar 08, 2007 2:06 pm

so basically those amp power kits are useless, since the ground is only like 4 feet

Post by **Bfowler** » Thu Mar 08, 2007 2:11 pm

Francious70 wrote:Well, since a car is a closed circuit the best grounding point is the one of lest resistance, AKA the battery.

Unless you can magically make steel less resistive than copper, lead, and a battery.

*EDIT* You REALLY need to get ride of the body skirts mang. And who's X-kalade is that in the background?

i need to get rid of them? why? btw those are factory oem.....if i got rid of them there would be bare chasiss.

the Denali is my pops. he wont let me put in mad tite bumps

Post by **bdubs767** » Thu Mar 08, 2007 2:11 pm

fucktards

Post by **Eric D** » Thu Mar 08, 2007 2:27 pm

This debate depends on the vehicle in question. I have removed traditional grounds and ran equal sized cables from the amplifier in the rear to the battery up front for ground, and ended up with unbearable engine noise. In other vehicles it has helped.

In my opinion, the situation depends on the construction of the vehicle. Many older cars, newer cars with all steel underbodies, and all trucks, do not benefit in any way from running a separate ground cable. The steel of the vehicle is capable of passing “thousands” of amps of current with minimal loss, whereas even a 1/0 copper cable is limited to “hundreds” of amps.

If the battery is grounded well to a structural member, and the alternator, head unit, and amplifiers are also, there will be far less chance of noise.

I would not be surprised if this philosophy falls short on newer foreign vehicles. They tend to use more exotic materials such as aluminum, and likely isolate steel from the aluminum to prevent galvanic corrosion. These junctions are poor conductors, and would attribute to a high ground resistance.

I would suggest anyone in car audio DOES NOT install a separate ground cable, and then if they experience engine noise, or find a substantial voltage drop at the amplifier, they then invest the money in a large gage ground cable to see if the situation improves.

Why spend money on something you most likely do not need?

Post by **Bfowler** » Thu Mar 08, 2007 2:46 pm

well the debate in BMW is a little different because battery is in the trunk, so grounding to the batter is often as easy or sometimes even more easy then a traditional grounding point.

so i guess what im asking is....what is the downsize of grounding to a battery. (assuming the the amount of work, and cost are almost identical

Post by **Eric D** » Thu Mar 08, 2007 4:14 pm

If the battery is in the trunk, there really is no point in grounding to the chassis. Just ground to the battery.

If the battery is up front under the hood, then running a separate power cable for ground may limit your current capability, and increase ground resistance. This depends on the vehicle and its structural design.

In the case of a truck for example, there is almost never a reason to run a separate ground cable. The chassis of the truck is far more capable of transferring current than a tiny 0/1 gage cable is. This assumes you actually ground your equipment to the chassis, not to the body which is sometimes mounted with rubber isolation pads, and not really all that large or electrically conductive bolts.

I personally ground to the body first (very easy to do with minimal effort). If I then run into problems I will look for a better ground point or possibly drill a hole through the body and find a major structural member to ground too.

For the most part, all of this is just basic electronics. Copper is more conductive than steel, but not really by a whole heck of a lot. With low voltage DC, skin effect is not an issue, so the important part is the cross sectional area of your conductor. Generally a large power cable is still significantly smaller than the steel’s cross sectional area between your equipment, even at its most narrow point.

If my battery were mounted on the left side of my trunk for example, and I mounted an amp on the right, I would still ground to the body or chassis (which ever is more accessible) at both the amp and the battery. After all, all the steel in between is very likely much more conductive than a power cable alone would be.

jbondox · Post by **jbondox** » Thu Mar 08, 2007 4:46 pm

ground to the battery, if the guyhas an issue give him my phone number

something to ponder.....

you have a 4 gauge input to your amp.... but an itty bitty trace to the toroids....

it is all about current capacity of the wire,and voltage drops along the way. ground it atthe battery if it is available

brenzbmr@sb · Post by **brenzbmr@sb** » Thu Mar 08, 2007 11:27 pm

well after looking at my e36
that has to be the most crappeist ground ever to try to pass all that
current through the whole car.

i ran my battery into the front of the car and i ran better ground connections in the front(big 3 or 6 or what ever the new slang is)
i also ran a solid ground with my pwer wire to teh rear.

i have no noise issues and less voltage drops then when it was in the rear.

jbondox · Post by **jbondox** » Fri Mar 09, 2007 6:12 am

well the e36 ground point we used for 2 1200.1 ti's and a 900.7 worked fine for us with no noise issues. or any issues for that fact. the stud for the ground, like a benz, is equivelant to a 1/0 cable to the frame. plus who really cares when the battery is grounded properly, and one is more concerned about the output current of the alternator