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  • Hooking up to battery.

    This is my first new/modern vehicle & I'm a bit paranoid about hooking up my air compressor to the battery with alligator clips.

    I've read that you hook the positive straight to the terminal (would the nut right next to it be sufficient?)
    The negative shouldn't be hooked up to the terminal? (would the nut right next to be sufficient? See photos)
    But hooked up to a bolt that is near the battery that is earthed to the body?

    The bolt that the battery earth's to is almost inaccessible as are most of the others near the battery.

    Any help would be much appreciated, I don't want to burn anything out.

  • #2
    First of all, I am not an electrician...

    I think the risk you are referring to is a spark igniting vented gas from the battery (which can then explode) and is not related to the type of vehicle or its electronics.
    This a genuine risk when attaching jumper leads from another vehicle as there *will* be a spark when attaching the final cable.

    I'm not aware that this is a problem when attaching a compressor. Everyone I know (myself included) go straight to the terminals. Maybe someone else knows better?

    In any case, I cant see how this advice would have anything to do with the type/age of vehicle. Attaching the negative clip to another ground shouldn't make any difference as far as the cars electrical system is concerned.

    Dave

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    • #3
      Originally posted by DaveC View Post
      First of all, I am not an electrician...

      I think the risk you are referring to is a spark igniting vented gas from the battery (which can then explode) and is not related to the type of vehicle or its electronics.
      This a genuine risk when attaching jumper leads from another vehicle as there *will* be a spark when attaching the final cable.

      I'm not aware that this is a problem when attaching a compressor. Everyone I know (myself included) go straight to the terminals. Maybe someone else knows better?

      In any case, I cant see how this advice would have anything to do with the type/age of vehicle. Attaching the negative clip to another ground shouldn't make any difference as far as the cars electrical system is concerned.

      Dave
      Thanks Dave.
      So the compressor hookup straight to the terminals should be okay.
      But if anyone knows where I should I jump start from in the case I do or someone else does get a flat battery it would be appreciated.

      Thanks.

      Comment


      • #4
        Hi Benicio, I'm not a auto electrician too.. But hey... this is what I would do... If I'm jump starting someone else's car, I will connect positive & negative terminals directly to the respective terminals of the battery (make sure the other ends of cable are not touching), but on the car with the flat battery, I would only connect positive cable to the flat battery's positive terminal. The negative cable, I would connect to a large bolt on the unpainted engine block of that car. Likewise the other way around if my car had a flat battery,

        For compressor, get one with or I'd make a inline fuse (just to be sure). I would connect the clamps straight to the battery. Run the engine, then switch on the compressor.

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        • #5
          Originally posted by Kiat View Post
          Hi Benicio, I'm not a auto electrician too.. But hey... this is what I would do... If I'm jump starting someone else's car, I will connect positive & negative terminals directly to the respective terminals of the battery (make sure the other ends of cable are not touching), but on the car with the flat battery, I would only connect positive cable to the flat battery's positive terminal. The negative cable, I would connect to a large bolt on the unpainted engine block of that car. Likewise the other way around if my car had a flat battery,

          For compressor, get one with or I'd make a inline fuse (just to be sure). I would connect the clamps straight to the battery. Run the engine, then switch on the compressor.
          Thanks Kiat

          This makes sense.

          Comment


          • #6
            I'm an elec eng not an auto elec so I may be corrected, but my understanding is that electrically any chassis connected point is equivalent to the negative terminal. Therefore technically you can connect the negative alligator clip to any of the above options.

            As Kiat said, I highly recommend using a fused connection, I've seen a few compressors with damaged cable insulation from wear and tear. Compressors pull a lot of amps and therefore have reasonablly heavy gauge wire. If that cable shorts to any part of the vehicle you'll be lucky if all that happens is the cable just melts. I use an Anderson plug mounted on top of my trailer electrical connector, other end connected to battery in engine bay via 50amp fuse. An auto Elec can do this for you in 30 mins.

            jump starting a car is a whole other can of worms. The last (negative) connection is usually to a substantial metal point in the engine bay away from the battery ( and moving parts) due to the spark generated. Again electrically it's all the same. Problem is the ecus, jump starting introduces electrical spikes that can smoke all sorts of sensitive electronics. When I've had to jump start I will hook up the batteries as discussed and run the starting vehicle for at least 5-10 minutes with the revs above idle, this will provide some charge to the flat battery and reduce the starting in rush current. Not claiming this is correct, it's just what I do...

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            • #7
              Thanks Gary.
              My compressor (Dr Air Pro Flow 150l) has a circuit breaker on it.
              Not sure if it does the same thing as a fuse tho.

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              • gary
                gary commented
                Editing a comment
                Yes the circuit breaker will do the same as a fuse. I assume your breaker is on/at the compressor? If so this will protect the compressor from over current situations, but if you short something "upstream" from the breaker then the breaker won't "see" the over current. That's why I always run my accessories off a fuse as close to the supply battery as possible. This fuse should have sufficient capacity to run all of your accessories. I have 3 seperate anderson plugs around the vehicle all running off one 50amp fuse mounted on the second battery.

            • #8
              Thanks Gary.
              ​​​​​​Yep the circuit breaker is on the compressor.
              Might look @ getting an inline fuse.

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