Waking up to your semi truck not starting can put you in a pickle. Now, you’re asking yourself, “How many amps to start a semi truck?”
Semi trucks require 1,500 to 2,000 amps and 24-volt batteries to start. However, some models may only need as low as 400 amps to ignite their engines.
Different factors can also affect the required amperage to start a semi truck’s engine. Read on and learn more about the necessary amps to ignite this vehicle’s engine.
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How Many Amps Does It Take To Start A Semi Truck?
As mentioned earlier, semi-trucks generally draw 1,500 to 2,000 amps to start their engines. However, note that this amp draw range is typically for using 24-volt batteries.
On the other hand, 12-volt vehicle batteries, especially those for North American trucks, generally have different amperage requirements. In particular, the amp draw will be as much as international 12-volt batteries.
In addition, the available power or voltage in the truck’s battery will affect the power required to crank the engine. You’ll find the typical power requirements to start a semi truck’s engine:
| Available Power from Battery | Power Required to Start Engine |
| 100% | 100% |
| 65% | 150% |
| 40% | 210% |
| 25% | 350% |
For example, the two 12-volt batteries of a semi-truck are now at 65% power. If the engine normally draws 1,500 amps, it may now require 2,250 amps to start. Also, a truck may only start with 4 batteries, especially on a cold day.
Factors Influencing Starting Amperage
Various factors can affect the amps needed to jumpstart a semi truck, as explained below:
- The starting amperage reduces in cold weather. It’s because it would take more power than usual to let the battery reach normal operations due to the reduced temperature.
- Also, the condition of the semi truck jump starter plays a vital role in this procedure. A weak starter may have issues drawing the necessary amps to start a truck’s engine.
- The battery’s cold-cranking amps can also play a role in the amperage needed to start a truck’s engine. This rating measures the effectiveness of a battery to crank an engine when in cold temperatures.
- Engine size is another factor that directly influences starting amperage – the larger the engine is, the more amperage you’ll need.
For instance, semi trucks have bigger engines than pickup trucks, resulting in their higher amps requirements.
| Pickup Truck | Semi Truck | |
| Cold Cranking Amps (CCA) | 400 to 600 CCA | 800 to 1,000 CCA |
| Moving Amps | 40Ah to 70Ah | 100Ah to 250Ah |
| Volts | 9 to 12 Volts | 12 to 24 Volts |
Conclusion
Remember, finding out how many amps to start a semi truck often requires looking at different factors. For instance, check the engine’s size and the ambient temperature. Also, don’t forget to inspect the temperature in the immediate environment.
It’s also possible to jump-start a semi truck’s engine using another car’s battery. But you must typically match the number of batteries with the truck’s power source to ignite the engine successfully.
I am Andrew Wright. With 8 years of experience designing, installing, and maintaining electrical power systems. I love my job, and I have always wanted to offer others the necessary help so they can take care of their houses.