The Covid-19 pandemic has been a real killer, not only of people but also car batteries and alternators. Several aftermarket suppliers have told us that battery and alternator sales have been up this year, and they attribute that to the change in driving habits that have occurred as a result of the pandemic. With more people working from home and many people out of work altogether, Americans are driving far less than they used to. And when they do drive, it is often just a short trip to a grocery store, Target or Walmart to stock up on groceries. With less commuting and pleasure travel, cars are sitting longer between trips and are not being driven often enough or long enough to keep the battery charged.
Lead-acid car batteries in late model vehicles can quickly run down when a vehicle sits for 5 or more days without being driven. All keep alive memories in many onboard electronics create a steady low current drain on the battery when the key is off. So over time, the current stored in the battery will gradually be siphoned down until the battery may be so low it won’t start your engine.
A chronically undercharged battery will often result in premature battery failure.
Changes in driving patterns caused by the pandemic is killing many car batteries.
Driving your car allows the alternator to recharge the battery. But it takes about 15 to 20 minutes of driving (not idling) to maintain battery charge. Alternators don’t put out much current at idle and need to be spun at higher speed to produce enough current to meet the electrical needs of the vehicle AND recharge the battery. If the headlights, heater, defrosters, heated seats and radio are on and pulling current from the charging system, they may not be enough amp output to also bring the battery back up to full charge. When lead-acid car batteries are chronically undercharged, the cell plates become sulfated and lose some of their capacity to accept and hold a charge. Over time, this results in a permanent loss of storage capacity and weakens the battery. The end result may be your engine won’t start or premature battery failure.
Less Driving & More Idling Is Hard on the Alternator Too
A low battery , infrequent driving and idling for long periods of time (as when waiting in line for a Covid-19 test or shot, or a fod pantry pickup) can really overwork and overheat an alternator. With normal driving or highway driving, the alternator is spinning fast enough to provide plenty of self-cooling (there is a fan on the alternator pulley for this purpose). But at idle, there is a high electrical load on the alternator and very little cooling taking place. Consequently, the alternator can overheat leading to failure of the alternator.
There are three pairs of diodes in the back of an alternator that are part of the “rectifier” assembly. The diodes convert the alternator’s Alternating Current (AC) output to Direct Current (DC). If one of the diodes in a diode pair gets too hot and fails as a result of being overworked, it reduces the alternator’s output by a third. That puts even more load on the remaining diodes, which will likely lead to more failures. If a second set of diodes fails, the alternator’s output will drop by two-thirds, which will likely soon lead to the complete failure of the third set totally killing the alternator.
A dead alternator can’t meet the electrical needs of your vehicle or recharge the battery, so the battery will quickly run down leaving you stranded when your engine quits running.
A fully discharged battery can be recharged but it won’t do you much good if your alternator is bad and can’t keep the battery charged. That’s why your charging system needs to be tested if your battery has run down or failed.
Charging System Checks
Most retail outlets and auto parts stores that sell car batteries will do a free charging system check. Two things need to be tested: charging voltage and current output. Charging voltage can be easily tested with a voltmeter when the engine is started. It should be about two volts higher than battery voltage (around 13.5 to 14.5 volts) if the alternator is producing normal voltage.
A current output test requires a charging system tester that can measure the maximum current output of the alternator and its voltage pattern. One or more bad diodes in an alternator won’t reduce charging voltage but they will reduce how much current the alternator can produce. One or more bad diodes in an alternator will produce an uneven ripple voltage when observed on a charging system tester.
If your alternator fails either a voltage or current test, you need a new alternator. Figure on spending $300 to $600 or more depending on the year/make/model of your vehicle and the labor required to replace the unit. Some alternators are relatively easy to change while others are not.
The cost to replace an alternator can range from $300 to $600 or more...
Related Articles:How To Test Your Alternator
Alternator Failure Causes
How To Replace an Alternator
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Battery Disconnect Problems (Read This BEFORE Disconnecting or Replacing Your Battery)
Diagnosing A Battery That Runs Down
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