Winter whoas?

| August 31, 2006

Preparation ensures cold weather starting and running.

Many truckers idle to prevent starting problems on cold mornings. But with fuel only increasing in price and anti-idling laws popping up in many areas, overnight idling is no longer the easy way to operate in winter.

Everything works against diesel engine starting as the weather gets colder. The cold, thick oil slows the engine down so much that a starter that draws 700-900 amps at 70 degrees will draw 1,800-2,000 amps at frigid temperatures, says Bruce Purkey, president of Purkey’s Fleet Electric. A battery that works fine in warmer weather could let you down on the first cold day. Testing your batteries and the cable system that delivers the juice to the starter, and making necessary repairs, will help.

“Nobody ever checks the cables. You can’t just look at them,” Purkey says. You need to do an electrical test. For every 1-volt drop in voltage through the cables, you will lose 30 rpm at the starter.

There are sophisticated testers for doing this. But you can also use a clip-on ammeter and a voltmeter. Voltage measurements will be meaningless unless the engine is cranking and lots of amps are flowing through the circuit. That means you’ll need to get somebody to crank the engine for you while you take measurements. Have your instruments ready so you can read the voltage and amperage before the engine fires. Connect the voltmeter between the bare metal of a battery or starter connection and bare metal on or directly attached to the frame or engine block.

First, measure the voltage at the connection on the starter where the battery positive cable connects. Then go back and measure the voltage at the battery connection, and subtract the lower voltage from the higher one. Voltage drop should not be more than 1-2 volts.

“It’s just as important to check the ground,” says Purkey. Measure the voltage at the ground cable connections, too, in the same sequence. If there is a cable between the starter and a ground strap, and another at the frame or battery box, measure the voltage between both the battery and starter connections, and the frame, and then add the two figures. More than 1 volt between the starter and batteries shows high resistance in the system.

If you get a voltage drop, you might want to clean up the connections with sandpaper or steel wool and reassemble snugly, then retest before replacing the cables. Replace battery cables – both positive and ground – that show a voltage drop.

“When it comes to battery testers, you get what you pay for,” Purkey says. “A $45 hand-held unit will give you a test that won’t mean a lot. Go to a reputable manufacturer like Autometer, Midtronics or Argus Analyzers.”

Such testers are affordable for the serious do-it-yourselfer. Jim Hamann at Argus Analyzers reports that the company has two models appropriate for use on a big rig. The AA400 sells for $299 and the AA500 for $399. Hamann says these high tech testers apply a heavy load for a brief time and use that to calculate the battery’s internal resistance, “the holy grail of battery testing.” This works because batteries fail when something prevents the unit from passing enough current. The unit gives you a percentage figure that tells you how much of the battery’s life is left, Hamann says.

Once you know a battery is bad, replace it right way. The more evenly the load is shared among batteries, the longer you will go prior to having trouble, so “don’t mix and match,” Purkey says. Replace all the batteries in the box unless they are within six months of the same age. Also, stick with the same rating and brand so the performance characteristics are the same. This will pay off in reliability and long life.

Purkey says not to buy just by “CCA” or Cold Cranking Amps because the batteries with the most CCA often have only “half the cycling life.” Talk to your supplier and tell him how you use the truck. If you shut down and drain the batteries frequently, the best choice would be a Group 31, a “dual-purpose battery.” These can tolerate giving up a lot of their charge and having it replaced the next day, yet still have good cold cranking power.

Oil grades
Truckers are so used to 15W-40 oil, considered just about ideal from as low as +14 degrees F. up to well over 100 degrees, that they often forget it’s perfectly OK to run thinner stuff at the frigid times of the year. Detroit Diesel’s Scott Zechiel provides the standard SAE guidelines, which his company accepts as offering effective engine protection. Just dropping the oil grade to 10W-40 drops the minimum temperature all the way down to -4 degrees F.

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