Jump Starting

Discussion in 'Top Tips & Tricks' started by Munchie, Sep 12, 2007.

  1. Munchie

    Munchie Funster Life Member

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    In the hope this avoids damage to vehicles.

    Do not ever connect the earth from battery to battery as this can cause damage to the Engine Management system!! :Eeek:

    Always consult the vehicle manual. :thumb:

    The AA recommended method is:
    Before connecting any leads make sure the vehicles are the same voltage and that they're parked with their handbrakes on and ignition off. The vehicles must not touch as this can cause sparks or an explosion.


    Use the red jump lead to connect the positive terminal of the donor vehicle's good battery to the positive terminal of the flat battery.
    Then use the black lead to connect the negative terminal of the good battery to a suitable earthing point on the engine or chassis of the other vehicle. This earthing point must be away from the battery and fuel system.
    With both leads connected wait three minutes for the voltages to equalise before starting either engine.
    Start the engine of the donor car and allow it to run for a minute then, with it still running, start the engine of the other car and leave both running at a fast idle for ten minutes. Do not remove the jump leads while the engines are running as this can cause serious damage to the electronics on either car.

    If the jump leads get hot, then avoid a possible fire by switching off both engines and allowing the leads to cool.
    Turn off the ignition on both cars and then disconnect the leads carefully in the reverse order to the way that they were connected. Be careful not to touch the clips against each other or against the car bodywork. :Smile:
     
  2. GeorgeTelford

    GeorgeTelford Deleted User

    Even if you connect from chassis to chassis for the negative it still connects one battery negative to battery negative.

    Do not trust anyone who calls negative on a vehicle "earth", its the first clue that they have not got a clue what they are talking about.


    Have they been watching to many American TV shows/films, in the real world cars do not explode on contact.
     
  3. GeorgeTelford

    GeorgeTelford Deleted User

    PS this is not a dig at you Ken:Cool:
     
  4. RockieRV

    RockieRV Deleted User


    Hi George

    I am glad you have said that, because your first post does read as if you are :Wink:
     
  5. Jim

    Jim Ringleader

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    Sharon, that's is George's writing style but we are slowly bring him around to using smileys, as much as he hates them:BigGrin:
     
  6. steve&barb

    steve&barb Deleted User

    damn and there was me jump starting of me leisure battery
     
  7. Munchie

    Munchie Funster Life Member

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    What I posted was the recommendations of the AA.

    I had an XJ6 jag which was in the garage for service and an apprentice used it to jump another car off. The end result being it "fried" my engine management card. The garage replaced this at great cost. This prompted me to read the "manual" and Jaguar had a paragraph warning against used the "negative" terminal on the battery, but to attach the lead to the engine "body" I think they would know. :BigGrin:
     
    Last edited: Sep 12, 2007
  8. GeorgeTelford

    GeorgeTelford Deleted User

    BTW that AA guide does not allow for positive earthed vehicles, the look of surprise when people find out the hard way is priceless.

    So be sure that both vehicles are negative earth first (in this case earth is the conventional term, unfortunately)

    Just researched the reason for not using the negative terminal. Its to idiot proof the connection procedure, ie if you were to do it properly connecting via negative terminal would not be a problem with igition off....
     
  9. Munchie

    Munchie Funster Life Member

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    Out of interest could some of you look in your car manuals re jump starting and see what they say?
     
  10. RockieRV

    RockieRV Deleted User


    What's a car manual? :Rofl1::Rofl1:
     
  11. Munchie

    Munchie Funster Life Member

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    Posted the tip with good intentions based on info from engineer who serviced my jag and what I read in the manual and what AA had to say.

    Methinks I'll keep my own councel from here on in.
     
    Last edited: Sep 12, 2007
  12. GeorgeTelford

    GeorgeTelford Deleted User

    Hi Sharon

    You know, its the book the male looks at when everything else as failed :Doh:
     
  13. RockieRV

    RockieRV Deleted User

    Hi Ken

    Sorry, I'm in a jovial mood - didn't mean to rub you up the wrong way. It was a good tip, but as I am technically challenged I thought I would still partake :Smile:
     
  14. Munchie

    Munchie Funster Life Member

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    Hi Sharon, you didn't rub me up the wrong way. :Rofl1:
    I was posting and had to go do something when I finished the post yours had beat me to it. :BigGrin:
     
  15. pappajohn

    pappajohn Funster Life Member

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    hi,
    during my short lived apprenticeship(cant take orders) i was always told to connect the neg lead to a suitable engine/body point on the dead car LAST as, if the battery had been gassing, there was a chance of explosion if the lead sparked on contact with the battery neg. if connected to a different point it should be far enough away from the battery not to really matter if it sparked.

    im sure with the advent of the ECU/EMU connecting to all terminals could cause a power surge and 'spike' the ECU, but i have my own views on this and i've never experienced it, after all, the handbooks state ignition MUST BE OFF when connecting, presumably to isolate the ECU.

    the other point about not touching vehicles goes back to the days of chrome bumpers ect. if the cars were touching you already had an 'earth' connection so when the pos lead was connected this could spark and do the same as in explaination one.
    plus in the days of pos earth you would certainly know you got it wrong. if one car was pos earth and the other neg earth it would be the same as connecting two batteries POS-NEG and NEG-POS.(BANG)

    john.
     
  16. GeorgeTelford

    GeorgeTelford Deleted User

    Hi Ken

    Keep your own council? The beauty of forums is that info can and will be checked by others, nobody should expect their posts to be right all the time or even info they are passing on, I dont expect that and apreciate any effort to improve the info thats posted.

    The AA should know better than to assume all vehicles are Neg Chassis and explosions from Cars touching is ludicrous, that doesnt mean that you did wrong by posting it.

    Pappa

    The look's on the faces when they do get crossed is priceless, I have seen 2 instances of people crossing over
     
  17. pappajohn

    pappajohn Funster Life Member

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    done it myself when i worked on breakdown recovery. 4am, snowing, middle of north yorks moors. courting couple with radio on (dont know why)for hours and flattened battery. got pos and neg reversed for about 50 millisecs. in my tired state i scared myself stupid. never done it again.:Blush:
    john.
     
  18. Brambles

    Brambles Read Only Funster

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    It is my opinion, and through experience you should not use a vehicle with an electronic management sytem to start another vehicle with it's engine running. You should actually stop the engine of the donner vehicle after allowing the 'dead' vehicle to charge for a few minutes. The reason is the voltage dip that occurs when starting. The management sytems are desined to be immune to this large dip while starting, but once running any large voltage dip can really upset it as it will be up an running in full operational mode and doing all sorts of operational checks and looking for faults and doing it's job. It can easily detect faults that do not exist and lock out certain functions. It may even lock up the processor completely and fail to work until given a full power up reset by disconnectimg the battery for a few minutes and reconnecting.

    Regarding the negative connection lead it is normal to connect that second in case you drop the last clip you put on. Imagine connnecting the neg 1st, then the positive and when doing the second pos clip you drop it or even accidently rub it against a metal object. BANG!. If you drop the neg clip then it will be a lot safer as you will only have the charge current flowing.

    If you connect the leads with the doner engine running and say the 'dead' car has a shorted battery, then you will be putting a massive load on your alternator and it could damage it.
    So wise way is to cautiously connect the final lead. If the 'dead' battery is shorted, you will know about it. The reason recommendation is to connect to part of the chassis/engine is so you do not get a large spark next to the battery.

    In summary. If the vehicle you are tryingto jump has been attempting to start but just flattened the battery in doing so or is a result of lights being left on etc, then fine. Battery should be ok and should not cause damage to doner vehicle.

    If 'dead vehicle is an unknown, say for example been sitting for a week and you have no idea of the condition of the battery and appears very dead. DO NOT even attempt to jump start from your good vehicle .. just not worth the risk. Best way there is to use a spare battery to give a jump, but better still to initally put a battery charger on to make sure battery wil start to charge. After it is brought up to 12 volts approx, then you can jump start.

    I think that all makes sense, over to George T to comment if it makes sense as easy to write what I think is right but can be read differently, especially at this time of night.
    Jon.
     
  19. kands

    kands Read Only Funster

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    Very nice, clear and concise post Jon, thanks. I am sure that there is no room for confusion on this important subject now.

    Keith
     
  20. Supertractorman

    Supertractorman Read Only Funster

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    Many LGV Transport Companies recommend to Drivers when jump starting, that the Donor vehicles engine is running and all lights, heaters and other electrical equipment is switched on on both vehicles in case of surge damaging ECU units etc
     

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