Why do Diesel Trucks Have Two Batteries?

If you’re a new diesel truck owner, you may pop the hood for the first time and find yourself in for a shock! Diesel trucks have two batteries , as opposed to most cars, which have only one. Diesel trucks need two batteries so they can crank at a higher amp. This is needed because a diesel engine demands a high-resistance load to start successfully. In simple terms, a diesel engine needs much more power to turn the engine over than a gas engine ; just under double the amount of energy, in fact.

The pair of batteries in a diesel truck can either be connected in parallel or in a series. Below, let’s take a closer look at these two setups and what they mean for your truck.

Most modern diesel trucks use a parallel-joined battery set up in a 12-volt system. A parallel connection means that both the positive and the negative terminals of each battery is connected to the others, meaning that the wiring has a criss-cross appearance. The benefits of a parallel set up include an increase in the rating of the current with a consistent voltage. What this means it that the overall energy output of your truck is high, but it will not surge. This safeguards the other electrical components of your truck. Conversely, the main drawback of this type of battery layout is that, in order to avoid burnout, your batteries will need to use a heavy-duty cable , which can be more costly to replace.

It is very rare that truck batteries are configured in a series, and many truck specialists would advise to steer well-clear of this setup. When batteries are connected in series, the voltage of each battery is added together but the amperage is kept the same. Batteries connected in series have a linear appearance and are perfect for use when a higher voltage is required. However, it can be very costly if incorrectly installed within your truck, as the high amount of voltage is likely to fry the electrical systems of your vehicle.

Truck batteries can be expensive to replace, which means that it is always best to care for your existing set to ensure they last you as long as possible. While the warranty on most truck batteries is 3 years, battery life could extend beyond that timeframe. You should pay a mind to how your batteries feel and perform and use this as a guide to decide when a new pair is required.

Driving in excessively cold or excessively hot weather can reduce the overall projected lifespan of your batteries, as they tend to place greater strain upon them. Corroded connections can also be a leading reasons as to why you may need to replace your truck’s batteries faster than usual, as corrosion impedes the voltage from the battery reaching the starter. An overcharged alternator can also be catastrophic for projected battery life.

You can be proactive in looking after your truck’s battery life by undertaking checks to the connection ports as well as the batteries itself. For example, checking the charging rate of the alternator as well as the water level can help reduce the rate of battery deterioration. Keeping the batteries clean can also help extend their lifespan, as it can help to reduce the risk of corrosion forming . If your battery is already showing early signs of corrosion, you can carefully clean this to extend the lifespan of the batteries.

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