Overdrive Magazine | Trucking Business News & Owner Operator Info
Issue link: https://read.dmtmag.com/i/85420
BATTERY MAINTENANCE Alternator maintenance is more about maintaining the batteries than the alternator itself. A good alternator lasts almost forever, but only if it doesn't overheat. One good way to prevent such overheating is to keep the batteries working efficiently. The alternator's main job is to handle the vehicle's electrical load, calling on 75 percent or more of its output. New batteries and good wiring reduce battery charging needs, making life a breeze for the alternator. As batteries and cables develop resistance, the alternator works harder and longer to replace what's used for starting or supplying overnight shutdown loads. Testing batteries once a year, preferably just before the weather gets cold, is critical. Testing reliable start power 1 Disconnect the cables to isolate the batteries. 2 Use a carbon pile load tester – a big electrical resistance – to put half the rated load on each. 3 Check the output voltage for 20 seconds of continuous loading with a voltmeter. If the voltage stays at or above 9.5 volts for more than 20 seconds, the battery will get you started. Voltage on a battery that is close to failing will fall off by the end of 20 seconds. If any battery fails this test, replace the entire set to ensure long life. You can inexpensively have this test done at a dealer or repair shop if you can't do it yourself. While this test will help ensure reliable starts, it's harder to determine whether batteries are gradually starting to tax the alternator by losing their reserve capacity, notes Bruce Purkey, president of Purkey's Fleet Electric. He suggests two ways you can check on this: Testing reserve capacity 1 Establish a baseline for good batteries by testing them when new. • Turn off the engine. Measure battery voltage. • Turn on headlights and let them drain the batteries for 30 minutes. Retest the output voltage and record the reading. • After a year or two, you can repeat the test. After 30 minutes, if voltage drops more than when new, it shows a reduction in reserve capacity. 2 Carefully monitor battery performance while shut down overnight if you have an inverter with a low-voltage cutoff. If your typical overnight load is fairly constant, note how long it takes to get a low-voltage warning or cutoff. When that interval becomes significantly shorter, it's time to replace the batteries. 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. FEBRUARY 2012 OVERDRIVE 35 Battery grime should be cleaned periodically. Corroded connectors need to be cleaned with an abrasive material or special battery post clean- ing tool. Resistance in these connections will reduce cranking power as well as prevent the bat- teries from being quickly charged after a cold start. Use a special, circular wire brush to clean battery posts. Some can be chucked into a drill to speed the pro- cess and do a more thorough job. John Baxter John Baxter