Here you’ll find an easy-to-follow step-by-step guide to jump starting a 12 and 24 volt battery system.

Most cars will have a 12v battery. 24v batteries are typically found in small commercial and light goods vehicles. Cars/small vans that have a 24 volt battery systems use two 12 volt batteries alongside each other, therefore the system needs to be treated as two separate batteries.

How to Jump Start a 12 Volt Battery

Using another vehicle

  • Before starting, make sure any electrical systems or devices in the car are turned off (Lights, CD player, internal sat-nav etc).
  • Remove the key from the ignition and keep the key away from the car.
  • When using another vehicle to jump start the dead car, ensure the working car is turned off before connecting the jump leads.
  • Connect the positive lead to the positive battery terminal of the dead car, then the other end to the positive terminal of the working battery.
  • Attach the negative lead to the negative terminal of the working vehicles battery, and then connect the other end to the negative terminal of the dead battery or any exposed fixed metal part of the non-working cars engine.
  • Make sure that the jump leads do not fall into either engine compartment.
  • Turn the engine of the working vehicle on and let it run for roughly five minutes to allow it to charge the dead battery.
  • Start the dead car and carefully remove the cables in reverse order.

Using a battery charging/booster pack

  • Ensure all electricals are switched off and remove the key from the ignition.
  • Make sure the battery charger is turned off.
  • Attach the positive lead to the positive terminal on the battery.
  • Connect the negative lead to either the designated terminal or a non-moving uncovered metal part of the cars engine.
  • Turn the booster pack on and allow to charge the battery.
  • Switch on the engine, turn the battery pack off and disconnect the cables, starting with the negative one first.

How to Jump Start a 24 Volt Battery

Use the above processes for each of the batteries. Make sure that when you’re changing the cables over from one battery to the other that you turn the engine of the assisting vehicle or the power of booster pack off before disconnecting and reconnecting the cables.

Both batteries can be charged at the same time using another vehicle and booster pack simultaneously.

As before, ensure all electrical units on the car are switched off and the key is removed from the ignition.

  • Ensure the charging pack is turned off and connect it to one battery. Attach the positive cable to the positive terminal and then attach the negative cable to the negative terminal of the same battery.
  • Using regular jump leads, attach the cables to the other battery. Do not attach the other ends to the working vehicle yet. Connect the negative cable to the negative terminal first, followed by the positive.
  • Turn on the booster pack and now attach the jump leads to the working vehicle and turn the engine on, allow the working car to run for five minutes.
  • Start the engine of the dead vehicle and turn the engine off of the rescue vehicle. Let the ‘dead’ (now hopefully working) car run for a few minutes.
  • Turn off the engine of the dead car and disconnect the booster pack. Switch it off and remove the negative cable first. Do not remove the cables of the battery pack whilst the engine is running.
  • Switch the car back on, and remove the remaining cables.

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