Can I Jump Start a Semi Truck?

January 2, 2020

The Rolling Rig

Keep a worry-free truck with these maintenance tips!

If you’re considering taking up driving commercial vehicles, or becoming a diesel service tech, but are completely uninitiated – it certainly wouldn’t hurt to approach your new venture with some mechanical prowess in your repertoire. One of the simplest, but useful things you can learn is how to jumpstart a semi-truck. You might be thinking, “Well I know how to jumpstart a diesel truck – it’s virtually the same process.” While you may be right regarding diesel pickup trucks with one battery – the majority of larger diesel trucks, and certainly semis, carry more than one battery. Learning how to jumpstart a semi-truck is simple – but you must be mindful of how the two batteries are wired, as two separate methods depend on the configuration.

Is Your Semi-Truck Wired in a Series or Parallel?

A semi-truck with two batteries is wired either in a series or parallel. There’s a big difference between the two. When your 12V batteries are wired in a parallel scheme, the two batteries run alongside one another, giving you the power of 12V times two. Wiring them in a parallel scheme essentially turns the two batteries into one, allowing you to leverage the power of 24V instead of 12. This particular writing scheme gives much larger diesel engines the power they need to operate efficiently. We’ll start with the easiest and describe how to jumpstart a semi-truck wired parallel.

How to Jump Start a Diesel Truck with Parallel Wired Batteries

When you’re learning how to jumpstart a semi-truck, it’s critical that you’re aware of the battery layout. Parallel wiring looks and functions essentially just as the name describes – the batteries are wired side-by-side, with the positive of one battery wired to the positive of the next, then wired to the component. On the other side, running in the opposite direction, the ground is wired to the second battery on the negative side, runs to the negative post of the other battery, and finally, to the metal ground connection. This distributes voltage equally throughout the component but allows for a great number of amps. The higher the amps, the more overall current that’s allowed to flow through the system. Let’s get to the process:

  1. First, ensure that whatever you’re using to jumpstart the batteries is rated for 12V. Any less, and it won’t power – any greater, and you could ruin the batteries.
  2. It’s always best practice to hook the jumper cables to the battery closest to the starter. This sends the largest amount of energy to the starter initially, giving the truck the kick it needs.
  3. It’s worth noting that it’s easier if you know which battery is dead – you can hook directly to this one – giving it the additional power it needs.
  4. Attach one red clamp from the jumper cables to the red clamp of the dead battery, or battery you plan on jumping.
  5. Connect the other red clamp to the assisting battery (the vehicle that’s jumpstarting the truck).
  6. Connect the black clamp to the assisting vehicle’s negative post.
  7. Connect the corresponding black clamp to a piece of metal somewhere in the vicinity, preferably as far away from the battery as possible. This keeps it grounded.
  8. Start the assisting vehicle, allowing it to idle for about five minutes.
  9. Start your semi-truck, giving it a slight amount of gas if needed. When it finally turns over, allow it to sit connected for about 15 minutes and continue to charge.

How to Jump Start a Semi-Truck Wired In Series

When your semi-truck batteries are wired in series, you’ll need to wire the jumper cables in series also. This takes two sets of cables. Use the list below to complete the process:

  1.   Connect the red clamp to the positive post on one battery, and attach the black clamp to the positive of the assistive battery.
  2. Connect the red clamp to the negative post on the outside of the OTHER battery.
  3. Connect the black clamp to the negative post of the assistive battery.
  4. Allow it to sit for a few minutes as you would using the other method.
  5. Crank it, and let it sit for 15 minutes.

Get Additional Trucking Tips from International Used Truck Center!

Now that you know how to jump start a semi-truck, you can confidently drive around . International Used Truck Center is your best source for truck driving tips, including brake maintenance and tire maintenance! If you have additional questions about how to jump-start your semi-truck, contact us or visit us today!

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