600 or 800 Amp jump leads?

Discussion in 'Electronics' started by wemorgan, Oct 14, 2011.

  1. wemorgan

    wemorgan MB Enthusiast

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    My car battery is rated at 730 Amps. I presume this is the maximum current drawn? So do I assume I need 800 A rated jump leads?

    The reason I ask is that 800A leads are a lot more expensive than 600A, so would rather buy the 600A if they're good enough.

    Thanks.
     
  2. Dieselman

    Dieselman Banned

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    I would buy the highest rating as it's a one off purchase and a diesel really does draw some current.
    Mine are old and a bit lightweight and I've felt them get rather warm a couple of times.
     
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  3. OP
    OP
    wemorgan

    wemorgan MB Enthusiast

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    Thanks Will. £20 from Amazon wasn't so bad really.
     
  4. Dieselman

    Dieselman Banned

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    That £20 would pale into nothing if one cold day you couldn't start your car.
     
  5. fatdazza

    fatdazza Active Member

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    Sorry to hijack thread but a mechanic once told me not to try jump starting my W203 C180k -I was a bit surprised, but he said it could screw up the electrics. Can anyone support this (I think there tends to be better advice given on this forum:D)

    Thanks
     
  6. OP
    OP
    wemorgan

    wemorgan MB Enthusiast

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    £20 is a nice insurance policy to be kept in the boot. :)
     
  7. Dieselman

    Dieselman Banned

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    It can fry the SAM unit.
     
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  8. fatdazza

    fatdazza Active Member

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    Is there any way of protecting against frying the SAM unit. Or what do I do in the event of a flat battery?
     
  9. Dieselman

    Dieselman Banned

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    Pray...
     
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  10. fatdazza

    fatdazza Active Member

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    But to which God - there are so many:confused:
     
  11. Howard

    Howard MB Club Veteran

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    Turn on some consumers before you connect the leads , helps lessen the spike on connection.

    Headlights should do.

    Bahahahahahahahha !!!
     
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  12. grober

    grober MB Master

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    Car starter motors usually run around the 0.8-1.2 horsepower mark = 600 to 900 watts. In practice due to peak current loading and frictional losses this equates to a momentary load anything between 150-300amps. The key word here is " momentary" since current demand is greatest as the starter has to overcome the inertia in the system. This drops off markedly as the engine begins to turn over. I doubt if the starter cable in the car has much more than a 70amp continuous rating anyway. With starter jump leads the higher the cross section the lower the voltage drop for a given current over a fixed distance. So the thicker the better really. This is more marked of course the longer the leads are. What you are paying for is really raw copper and the quality of the clamps.
    The CCA or amp hours rating of the battery doesn't really come into it. THIS OLD REVIEW MIGHT HELP YOU. Jump Leads Review | Car Jump Lead | Battery Leads | Auto Leads | jump Start Battery | AutoExpress
     
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  13. CKLclive

    CKLclive Banned

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    you should have bought some HD ones lol:rolleyes:
     
  14. Danny DeVito

    Danny DeVito Active Member

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    According to WIS consumers should be off. Connect leads then start donor car. Careful attention to correct voltages and dont cross leads. IIRCWIR
     
  15. Dieselman

    Dieselman Banned

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    Yeah, well 20 years ago I didn't need such good ones and they have always worked OK, just got hot a bit hot a couple of times.

    Bigger diesels do suck some juice.
     
  16. Dieselman

    Dieselman Banned

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    Starters for diesels are generally 1.2-1.5Kw, so require significantly more current.
     
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  17. jaymanek

    jaymanek Authorised Forum Sponsor Authorised Forum Sponsor

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    Get that fattest ones you can afford! Trust me the thin ones just dont work!


    With reference to damage, I have never ever damaged any control unit by jumping.
    You need to connect the leads with donor car switched off, then start the good car and let it charge for a while.. Then have a go at starting the bad car.
    Then leave the leads connected for say 30 seconds so as not to cause a spike... then remove from the good car and then from bad.
     
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  18. DSM10000

    DSM10000 MB Enthusiast

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    The resistance of a wire is directly proportional to the length of the wire and inversely proportional to the cross-sectional area of the wire so the "thicker" the wire the lower the resistance and therefore lower the voltage drop and current loss.
     
  19. fatdazza

    fatdazza Active Member

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    So, short and fat is good - just like me :D
     
  20. WOODYTHEWISE

    WOODYTHEWISE MB Enthusiast

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    Hi,it says in my handbook (CL600) "ON NO ACCOUNT TURN ON THE HEADLIGHTS" this may not apply to your vehicle, but thought it worthy of mention.
     
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