Electrical PM

John Baxter | February 01, 2012

Conventional batteries require regular addition of distilled water. Keep the cells filled for maximum performance and life, doing so once a month. When doing your monthly check of electrolyte level, carefully wipe off the top of every battery. Do this for maintenance-free batteries, too. Keeping batteries clean reduces the loss of charge during shutdowns.

Conventional batteries have the advantage that the density of the electrolyte liquid in the cells can easily be tested with a hydrometer. Remove the cap from each cell, draw a sample of electrolyte into the hydrometer, and watch what the indicator balls do. If they rise to the top of the fluid, the cell is charged. If they sink, the cell is bad, and the battery should be replaced. Always return the electrolyte to the cell once tested. Testing every six months is an excellent way to anticipate battery trouble.

Maintenance-free batteries have an indicator that changes color when they deteriorate. Check your owner’s manual for a description of how the indicator should look. When its color changes, have the battery checked and, if necessary, replaced.

More battery PM tips

• Clean and tighten connections. Twice a year, disconnect all the battery connectors and use a powered brush to clean both the inside diameter of each connector and the post. Reconnect all connections securely and then protect them with di-electric grease or a spray protectant. Note that typical, soft lead connectors continually stretch. Tighten the fastening bolts once a month to ensure maximum conductivity, or get plated brass connectors that are much harder.

• Beware cold temps. Cold weather affects a battery’s ability to give up stored power and to allow recharging. “A battery will lose 35 percent of its cold cranking amps at 0 degrees Fahrenheit,” Purkey says, “so you need a full battery charge to ensure reliable starting. Also keep in mind that a jumpstart may not be enough to get the truck ready for a shutdown even a few hours later. At cold temperatures, it can take as long as two days for batteries to become fully charged.”

This means connecting the truck to a battery charger is the best way to get the truck back to reliable operation, says Tim Ruth of Warehouse Battery Outlet. “To bring a discharged battery to its full 12.6-volt charge, charge it at a low rate for 18-24 hours, not just 2 or 3 hours,” he says.

Wiring maintenance

Purkey says many a battery cable has been the real culprit when truck owners believe they have a charging or battery problem. So when checking your batteries before cold weather, inspect the cables, as well. The Technology and Maintenance Council’s Recommended Practice 129 calls for a voltage drop of 0.5 volts or less at 500 amps of current flow. If the voltage drop is greater than this, the cable needs to be replaced.

However, you can’t tell much by just putting a voltmeter on connections because resistance doesn’t show up until there is high current. So Purkey recommends having a professional test each cable with a special instrument that uses electronics to measure resistance. In four seconds a technician can tell whether a cable needs replacement.

Alternators and heat

As the wiring inside the alternator heats up, resistance increases, reducing the unit’s output. The windings inside have insulation and soldered connections that are sensitive to heat. As loads increase beyond what the unit was designed for, it can fail. An unusual load can have the same effect as inefficient batteries, producing a snowballing effect that means long hours at maximum loads, overtaxing the alternator.

You could also do this yourself. Measure voltage at the starter positive connector while the engine is being cranked by someone else. Then take a similar measurement at the battery positive terminal and subtract the first reading from the second. “It makes a lot more sense to replace a $4 battery cable than an $80 battery when the cable is actually the problem,” Purkey says.

He also recommends checking wiring quarterly, or whenever you see corrosion starting to develop. “If you can see green, there is more of it from corrosion that is still invisible,” he says.

More wiring PM tips

• Starter and alternator positive and ground connections and any ground wires on the chassis need to be checked to ensure connections are clean and tight. Inspect and, as necessary, clean any wiring connections, whether voltage or ground. You can clean the contacting surfaces with an abrasive like sand paper. Then reinstall fasteners tightly, replacing them if corroded.

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