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Jump Start Your Smart

Instead of bypassing the starter motor by push starting your smart, why not use the power from another car's battery to boost your own?

Modification Details




Important Information

Jump starting really is the last thing you should consider because the smart electrics are
very sensitive. I have seen ECU's and speedos fried after attempting a jump start from
another car. This can show up as many faults like:

Immobiliser not deactivating. (ECU fried)
Car not even trying to start. (ECU fried)
1 bar showing on speedo. (ECU fried)
Speedo dead. (Speedo fried)

To repeat

Not following the correct procedure can cause damage to your SAM, ZEE or ECU.
There have been quite a few reported cases of smarts being totally immobilised after being
boosted from another car's battery, therefore it is important to know and to get right.


Why Jump Start Your Smart?

If your battery is discharged below the level at which it can turn the engine and you are
sure that the starter motor isn't faulty then consider jump starting. Also if you do not have
the room or manpower to push start the smart then jump starting is the only option.

Why Shouldn't I Jump Start?

If the starter motor is the reason the car won't start, no battery will jump start it.
If the alternator isn't charging the battery then jump starting it will get the car started,
as soon as you disconnect the second battery the car will cut out again.

Prechecks

Find someone with the newest car you can, this is because newer cars have better batteries
and alternators meaning that there is less chance of a voltage spike killing your car.

Any normal car will have a battery suitable for starting a smart. Don't use a lorry or a truck as they
tend to be 24 volts. Check the voltage rating on the top of their battery. It must be 12 volts.


Find, borrow or buy some jump start cables. Let's be honest, you won't have some in the boot.

Fitting The Jump Start Cables

There is a subtle difference between what is stated in the fortwo manual to other models.

Smart Fortwo 450 And 451
  • Make sure both cars are turned totally off.
  • Turn off all unnecessary electrical items such as lights and heaters etc.
  • Gain access to your battery, make sure you know where it is.
  • Connect the red clamp to YOUR battery's positive terminal.
  • Connect the second red clamp to the positive of their battery.
  • Connect the black clamps to the battery negative terminals starting with their car.

    Smart Roadster And Forfour

  • Make sure both cars are turned totally off.
  • Turn off all unnecessary electrical items such as lights and heaters etc.
  • Gain access to your battery, make sure you know where it is.
  • Connect the red clamp to YOUR battery's positive terminal.
  • Connect the second red clamp to the positive of their battery.
  • Connect the black clamp to the battery negative terminal of their car.
  • Connect the remaining black clamp to the engine block or ground point of your car.

    Jump Starting The Smart

    Again, there seems to be a slight difference between the manuals on how this should be done.

    Smart Fortwo 450 And 451

  • Get the other car running in neutral and wait for a minute.
  • Press the unlock button to turn off the immobiliser.
  • Start the car as you would normally.

    If the smart doesn't start, wait another minute and try again.
    Once the smart has started, leave it running for two minutes before disconnecting the cables.

    Smart Roadster And Forfour

    The smart manuals do not call for the assisting vehicle to be running.

  • Press the unlock button to turn off the immobiliser.
  • Start the car as you normally would

    If the smart doesn't start, wait another minute and try again.
    Once the smart has started, leave it running for two minutes before disconnecting the cables.

    Disconnecting The Cables

    After allowing the car to idle for a few minutes, remove the cables in this order.

  • Black clamp on your own battery.
  • Black clamp on their battery.
  • Red clamps from both batteries, no special order.

    After Care

    Leave as many of the unnecessary electrical items turned off as possible, obviously don't drive around in the dark with your lights off. This allows more power for charging the battery.

    Get the battery checked out by a professional garage or even a muppet at Kwik Fit or Halfords.
    Consider replacing the battery for a new one, once a battery has gone flat it is never the same.

    If you didn't 'accidentally' forget to give the jump cables back, go buy some just in case.

    Just To Cover Myself

    Don't lean over the battery when connecting the jump leads.
    Cleanly apply and remove the clamps each time to reduce sparking.
    Do not let the clamps touch each other (like Ghostbusters, don't cross the streams, that would be bad).
    Don't park the cars too close to one another as it is possible to get sparks jumping from one
    car to the other, although this may sound and look great, it's no good for your bodywork.

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