​​Why Do Diesel-Powered Vehicles Have Two Batteries?​

The battery is one of the most essential parts of a vehicle’s operation. Without one, you cannot start your vehicle, let alone give it the energy to create a spark, run your climate control system, infotainment, power windows, doors, seats, and your tailgate.

Some vehicles can do well with just one battery. However, there is a special circumstance that allows for two batteries to be placed underneath the hood. If you run a GMC with one of two Duramax diesel engines, it requires two batteries to operate. The question arises as to why you would need two batteries for a diesel-fueled vehicle.

As the RealTruck website explains, diesel engines operate differently than gasoline ones. They are higher in compression and require more demand from their 12-volt batteries. A single pickup truck (or SUV) battery cannot meet the demand from the engine. A second battery is added to provide additional energy to the electrical systems, such as powering the glow plugs. Both batteries supply power to various vehicle functions, including ensuring that the glow plugs operate as intended.

The glow plugs help ignite the spark in a diesel engine – the Duramax engines, for example. They serve as engine heaters, preheating the combustion chambers to assist with engine start. This is required when running a diesel engine in colder temperatures. Operating two batteries ensures better operation in any weather. You need all the cold-cranking amps to get your diesel engine going. This is one of the reasons why you might feel a slight delay when firing up the engine.

You will notice that the batteries are interconnected. A crossover cable is installed to ensure both batteries operate as intended. That also eliminates the need to prioritize one battery over the other. They simply work in tandem to get your diesel-powered vehicle running properly.

There is one benefit to having two batteries under the hood of your Duramax diesel-powered GMC: longer life. When both batteries are operating in good health, they can reduce overall strain on the electrical system while sharing the load to keep all of your electronics running smoothly.

If you have a Duramax diesel-powered pickup truck or SUV, Ewing GMC is here to assist. We have replacement batteries available through our parts department. Also, our service department is ready to keep your vehicle running year-round. If you have any questions about your Duramax diesel-powered GMC, please don’t hesitate to contact us.