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  • Why not ground to battery?

    Just a quick question(s):

    With people having so many problems with noise and whatnot, wouldn't a configuration wherein all powered devices shared a common distribution block wired directly to the negative post aid in some of these issues? Is this overkill?

    It seems that if i'm running wire anyway i might as well run two. Ridiculous?

  • #2
    Well I guess the main reason is that the negative cable goes from the battery to the chassis so you don't have to worry about making hole in the firewall, running a cable etc.

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    Originally posted by bgoodman
    We're an international forum, post in whatever langauge you like.

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    • #3
      It's not necessary. Ground to the frame or chassis.

      I typically try to keep my ground less than 18 inches or so. I'm guessing it'd take you at least 5 or 6 feet of wire to ground to the battery.
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      • #4
        the battery's negative goes to the car's chassis, by electrical conductivity the entire metal frame of the car is now connected to the engative terminal on the battery.
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        • #5
          But which has less resistance?

          With vehicles these days comprised of metal just tacked together, one has to question the resistance from the rear of the vehicle to the front. It would be a great experiment to determine the delta between the two.
          Take my advice: Do not try to build a system that includes EVERY feature. Start with the basics, build it to a bug free state, and THEN add on.

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          • #6
            Originally posted by Will Albers
            But which has less resistance?

            With vehicles these days comprised of metal just tacked together, one has to question the resistance from the rear of the vehicle to the front. It would be a great experiment to determine the delta between the two.
            The shorter wire would have less resistance than a longer to the negative battery terminal. Running a ground wire all the way back to the battery is a complete waste of time, wire, and would have more resistance than an appropriate, shorter ground.

            It sounds to me like you're imagining the current going from a ground, through the frame, all the way to the battery's ground, then to the negative terminal. If so, this isn't how it works. The "flow" of electricity does NOT have to terminate at the negative terminal of the battery.
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            • #7
              Originally posted by ITL
              The shorter wire would have less resistance than a longer to the negative battery terminal. Running a ground wire all the way back to the battery is a complete waste of time, wire, and would have more resistance than an appropriate, shorter ground.
              You seem to be only comparing a ground wire back to battery only with the ground wire to chasis. Of course the latter, being shorter, will have less resistance. But the chasis has a non-zero resistance as well, and while I think it's really just an academic point, I don't think it's a given that one path is going to have a lower resistance than the other (depending on wire gauge, chasis material and construction, yadda yadda).

              Originally posted by ITL
              It sounds to me like you're imagining the current going from a ground, through the frame, all the way to the battery's ground, then to the negative terminal. If so, this isn't how it works. The "flow" of electricity does NOT have to terminate at the negative terminal of the battery.
              It sounds to me like you're imagining a circuit doesn't have to terminate at the battery ground? It most certainly does, or you won't have a circuit. If the chasis were not grounded to the battery, it would not serve as a grounding point for electronics powered by the battery.

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              • #8
                Grounding to the battery
                Originally posted by ghettocruzer
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                • #9
                  Originally posted by mushin
                  It sounds to me like you're imagining a circuit doesn't have to terminate at the battery ground? It most certainly does, or you won't have a circuit. If the chasis were not grounded to the battery, it would not serve as a grounding point for electronics powered by the battery.
                  No, it doesn't always terminate at the battery ground. If the engine is running, the circuit will terminate at the altenator ground which (through the engine block) is connected to the chassis. This means that there is no point in wiring all the grounds directly to the battery because the flow will have to go throught the chassis anyway when returning to the altenator.

                  I believe The Big 3 upgrade would be the best solution (certainly it was for me).

                  Rob.

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                  • #10
                    I have a big ?????? regarding to 1 part of the big 3 upgrade. And that is battery + to alternator
                    In my cars (and most other cars), there is a fuse (rated at 100A) between the alternator and the battery. If you put a wire directly between the alternator and the battery, what is the purpose of the fuse that the manufacturer put in there (disregard about liability ****)?

                    Now regarding to the original question. Running a wire from where you want to the battery is seem to be a waste of time/money. Just run do a big 3 upgrade (2 ground for me) and you will be fine (most part).
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                    • #11
                      Originally posted by gommino
                      No, it doesn't always terminate at the battery ground. If the engine is running, the circuit will terminate at the altenator ground which (through the engine block) is connected to the chassis. This means that there is no point in wiring all the grounds directly to the battery because the flow will have to go throught the chassis anyway when returning to the altenator.
                      Oh yeah, I forgot about the alternator . Of course not all routes through the chasis are equal, so on some nitpicky level there's some difference, but the whole discussion's kinda absurd .

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                      • #12
                        Originally posted by MatrixPC
                        I have a big ?????? regarding to 1 part of the big 3 upgrade. And that is battery + to alternator
                        In my cars (and most other cars), there is a fuse (rated at 100A) between the alternator and the battery. If you put a wire directly between the alternator and the battery, what is the purpose of the fuse that the manufacturer put in there (disregard about liability ****)?

                        Now regarding to the original question. Running a wire from where you want to the battery is seem to be a waste of time/money. Just run do a big 3 upgrade (2 ground for me) and you will be fine (most part).
                        You should also put a suitably rated fuse in the extra wire you put in, within 18 inches from the battery.

                        Rob.

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                        • #13
                          i always figured it was cause the alternator connected to the battery directly and the alternator's electrically noisy
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                          • #14
                            The battery(-) terminal is your only true ground. chassis at rear of car can rise a bit underload, not volts but enough to give noise on (cheap)amps etc, the engine block can rise quite sharply when cranking.

                            Saying that, I have all my gear grounded to a nut/bolt through the boot/trunk floor, with a real thick cable from the battery(+) for it all. (note to self, must fit fuse)

                            Dont take power from the alternator, its noisy and spikey and it can be noisy enough to cause problems with most items that need a smooth supply.
                            Lez, more widely known as flez1966

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                            • #15
                              Originally posted by lez
                              Dont take power from the alternator, its noisy and spikey and it can be noisy enough to cause problems with most items that need a smooth supply.
                              Hate to break it to you, but there is no difference between connecting your power cable to the alternator and connecting it to the battery when using modern internally regulated alternators. Any noise or spike will travel to your system regardless of where you connect it.

                              Now component location is a different story. Alternators do make significant magnetic fields that can mess with compnents which are normally isolated from the power supply. Decent power supply filtering and shielding usually protect from this though
                              Take my advice: Do not try to build a system that includes EVERY feature. Start with the basics, build it to a bug free state, and THEN add on.

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