​​Why Diesel Trucks Have Two Batteries​ 

Diesel trucks are a popular option for people who need a reliable, long-lasting truck to tow and haul heavy loads, such as large yachts, multiple horses, a number of cars, and more. It is well known that a truck with a diesel engine not only holds its value but can be driven for hundreds of thousands of miles with only standard maintenance. However, there are some questions that people have about them, one of which is, why do they have two batteries? 

Two Batteries Means Less Stress 

All vehicles need a 12-volt battery to start it. Once it’s running, the alternator takes over and recharges the battery. But in diesel trucks with large engines, automakers add a second battery to reduce stress on both the battery and the engine during startup.  

Diesel Engines Are Different Than Gas Engines 

Since diesel engines in trucks are typically larger than their gasoline counterpart, they need more engine to kick over. Gas engines use spark plugs to ignite the fuel during the starting process, while diesels use more compression instead. By adding a second battery, the cold cranking amps (CCA) are effectively doubled, increasing the power available when you turn the key to start the truck.  

Dual Batteries Are Great When It’s Cold 

While both batteries operate at 12 volts, manufacturers wire them in parallel to increase power while reducing stress on the motor and evenly distributing the load. This is incredibly helpful, especially in colder temperatures.  

Why Diesel Trucks Use Glow Plugs 

Diesels often have glow plugs when operating in regularly cold climates. These are small heaters installed in the cylinders to preheat the engine when it’s extremely cold outside. Having an extra battery ensures the plugs heat instantly.  

Two Batteries Means Longer Time Between Changes 

Diesel truck owners typically don’t need to change their batteries as often, since there are two that handle the load evenly. However, because these vehicles have two batteries, you will end up spending double when getting new ones. While this doesn’t seem ideal, it saves money in the long run. You can even extend your batteries’ life by attaching a battery charger to them and plugging it into a regular wall outlet. This keeps the batteries topped up and in excellent condition for longer.  

There are plenty of companies that make smart chargers, such as Noco, Battery Tender, Schumacher, CTEK, Hulkman, among others. You can also purchase adapters that allow you to easily connect the chargers to the batteries. Just make sure you get a charger designed for 12-volt batteries and that it offers at least 5 or 10 amps of charging. You will need to purchase two chargers, one for each battery.  

Which Battery to Attach Jump Leads To 

If you find yourself in need of a jump start for your diesel, make sure to connect the jump leads to the battery closest to the starter, as this is the one directly connected via a red, positive wire to the starter.  

Alderman Automotive Can Answer Your Diesel Questions 

If you have more questions about diesel engines, the helpful sales team at Alderman Automotive can provide the answers you need, along with test-driving various models to find the right fit for your budget and lifestyle.  

Why Choose Alderman Automotive   

At Alderman Automotive, we work tirelessly to give you the best possible price and service on every used car we sell, and our finance department will work within your monthly payment needs. Whether you are looking for a high-end luxury car or SUV, or if your budget is something under $15,000, we have a whole host of vehicles best suited for your wants and needs. Our state-of-the-art service department and helpful staff will ensure your vehicle is always in the best condition possible.