This is why diesel trucks need two batteries
- Diesel trucks are known for their ability to do the heavy lifting
- The torque and power provided by diesel trucks make them perfect for heavy industries
- However, many people might not know that they use two batteries – and this is why
Published on May 19, 2025 at 12:09 PM (UTC+4)
by Keelin McNamara
Last updated on May 15, 2025 at 1:25 PM (UTC+4)
Edited by
Kate Bain
For those who don’t know, humans use diesel trucks for very good reason.
Unlike petrol engines, diesel engines are much better suited for heavy/powerful work.
The torque and power produced by diesel trucks make them ideal for the job.
But what you might not realise is why diesel trucks need two batteries under the hood.
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If you’ve ever looked under the hood of a gasoline-powered car, you’ll have noticed that the engine has a single battery.
However, diesel trucks and cars will actually have two batteries.
The majority of cars and vehicles have, for decades, used a 12-volt electrical system.
Naturally, you might think that this equates to a 24-volt system for diesel trucks.
However, that is not actually the case because the batteries are arranged differently.
In a diesel vehicle, batteries are connected in parallel in order to double the amperage.
At this point, you’re probably wondering why a diesel vehicle needs more amperage.
Interestingly, it is all to do with a topic called compression ratios.
Diesel engines have a much higher compression ratio than standard, gasoline engines.
This then makes diesel engines much more difficult to turn over and start.
That, in turn, means the battery has to work much harder to bring the diesel engine to life.
Most gasoline vehicles today currently have around 400 – 1000 amps in their batteries.
This means that a diesel car or truck with two 800-amp batteries would have the same 12 volts.
However, it would now have a mammoth 1,600 amps of electrical cranking power.
As we explained above, diesel engines require many more amps of power due to the compression ratio.
The parallel layout of the batteries allows for double the power whilst maintaining the same voltage.
If you think about it, it’s actually quite an ingenious setup for diesel engines.
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Keelin McNamara is a content writer at Supercar Blondie from Ireland, covering cars, technology, and lifestyle. Despite being a Law graduate, he discovered his passion for journalism during the COVID-19 pandemic, and has worked in the industry ever since. Outside of work, he is an avid MotoGP fan, and is a self-confessed addict of the sport.
