How Often Do You Need to Replace the Batteries in a Diesel Truck?

by K.K. LowellUpdated July 13, 2023
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It takes a lot of battery power to start a diesel engine, which is why these trucks generally have two batteries. The batteries should be replaced in pairs, but because It's expensive to replace two batteries at once you want to be sure you're getting maximum life from them. Replace them too often and you're wasting money. Wait too long and you might need a tow.

Factors to Consider

Battery life doesn't follow a schedule. Just because the warranty on a battery is three years does not mean the battery will suddenly go bad when three years is up. Many factors help determine when to replace the batteries in a diesel truck, or any vehicle. The first factor is frequency of starting and duration of running time. A higher load is placed on batteries that start the engine often, especially if the weather is cold and the running time is short. The glow plugs, small devices within each cylinder, have to be more frequently heated to the point where the incoming fuel will be ignited because the engine never reaches operating temperature. This is a major current draw. Short durations of running time mean shorter periods of recharging, which could leave the batteries in an undercharged state.

Temperature itself is a factor in battery life. Battery output is greatly reduced in winter -- especially in areas where winter is very harsh -- placing a much heavier load on the starting batteries. Here again, glow plugs factor in as during really cold-weather starts as the computer keeps the glow plugs on for a longer period. Conversely, hot weather places a strain on batteries, too. Summer heat evaporates water from the battery, which, unattended to, leads to internal damage.

The condition of the vehicle wiring and charging system also greatly affects battery life. Corroded connections may mean the full voltage from the battery is never delivered to the starter and electrical system, or that the voltage generated by the alternator is reduced in its trip to the battery. Additionally, an overcharging alternator can dramatically shorten a battery's life by boiling the water out of it, causing the same type of damage as summer heat, only faster.

Even something as simple as the condition of the battery terminals can affect battery life. Keep them clean and corrosion-free and the batteries last longer. One of the problems with dirty batteries is that the corrosion helps keep the top of the battery moist, possibly allowing a small current drain across the battery terminals.

Check These Things First

If you suspect that you have a battery problem, first check the alternator charging rate, the water level and the condition on all the battery connections on both the battery and starter or engine end. Remove the bolt and completely clean the connection if signs of corrosion are noted.

And Finally

The average life of an automotive battery is three to five years. If your truck is older than that, and there is a possibility of being stranded somewhere remote where help might be a long time coming, you might want to replace the batteries just as a precaution. Consider the cost of the batteries as an insurance policy against being stuck alone with no way to start your truck or get help.

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