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A little bit of planning will keep those batteries charged

By on July 1, 2013

Imagine waking up before sunrise filled with anticipation of a great day of trucking ahead of you, only to notice that your cab is far hotter than expected. You have a sick feeling about what’s coming next, but you go ahead and try to crank your vehicle.

All you hear is a frustrating clicking noise coming from your starter. Your voltmeter is noticeably lower than it should be. Yes, another set of batteries have delayed your delivery and taken hard-earned money out of your pocket.

You can avoid this scenario with just a little attention to your cranking and charging systems.

Drain, drain go away

Even when the key is in the off position, unplanned and unseen electrical pulls on the batteries may occur. These are known as parasitic drains and can often be traced back to one of the 10 or more computers on modern vehicles that operate the engine, A/C, lights and other systems. Many of these computers are turned off by a manual switch or programmed to go to sleep when not in use. Sleep mode helps prevent major parasitic drains but does not eliminate them.

If you notice that your vehicle seems sluggish, bring it in for service. A skilled technician will hook up a meter to your battery cable and monitor amp flow while unplugging circuit protectors until the unwanted amp flow goes away. Once the problematic circuit is identified, detailed troubleshooting will unveil the defect so a proper repair can be made and your batteries live to see another day.

Hidden rot

“Green cheese,” as the common green-colored corrosion that develops on batteries is affectionately called, can make it very difficult for the cranking system to obtain proper voltage from the batteries, especially in extreme temperatures. Though we tend to think of batteries straining in cold temperatures, hot weather is equally destructive. Extreme heat or cold will chemically damage the battery, causing it to go below the acceptable 80 percent charge state.

Corrosion makes it difficult for the alternator to charge the batteries effectively. It can cause the alternator to charge a clean battery at a higher rate than one with corroded cables. When the chemical reaction needed to charge a battery is exceeded by the discharge rate, that battery is doomed.

But the corrosion may be impossible to detect by a visual inspection, so this condition will likely require volt drop testing by a skilled technician. The connections and cables filled with “green cheese” can be corrected, and you will find that your batteries will choose to stay in that battery box for years to come.

Charged too much

Overcharging is a life sentence for the battery. It is typically caused by a bad alternator, loose or bad connections, or it could be one bad battery in a set of batteries. Some charging systems use a remote sense wire from the alternator to the batteries so the alternator can react directly to the electrical demand of the batteries. This remote sense wire has a fuse in it to protect the circuit. If this fuse blows or the circuit opens, the alternator will likely default to an overcharge condition and destroy your batteries. If you smell an odor similar to rotten eggs, your alternator is likely overcharging the batteries.

There’s also the age-old problem of slipped belts. When your belt slips, the alternator does not generate enough rpm to keep up with the electrical demand while the vehicle is running. That will result in the battery dropping to unacceptable charge levels.

Staying power

As you can see, your batteries are very sensitive to many different types of defects that can shorten their life. A standard electrical system check is very effective in helping to spot issues before they become a problem and so maximize the life of your batteries. This electrical check should include an evaluation of your alternator, all cranking and charging system cables and connections, alternator belts, alternator mounting, parasitic drains, battery condition, battery box and hold down condition, and a starter and mag switch circuit volt drop test.

A little electrical system evaluation and maintenance check twice a year will keep that clicking nausea away and keep your vehicle uptime and on time!

Homer Hogg, Technical Training Manager for TA and Petro, has worked as a truck technician for more than 30 years. He is ASE Master-certified, a Daimler Certified Trainer and a member of the Nashville Auto Diesel College Hall of Fame.


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One Comment

  1. Don Williams

    July 1, 2013 at 4:53 pm

    I visited with you at Skills USA on the diesel instructor opening we have at Washburn Tech in Topeka. You asked me to contact you as you may have some suggestions on ways to find instructors. Please contact me by e-mail at or by phone at 785-228-6305.

    Thank you,

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