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Bad car battery vs. Bad alternator

Bad car battery vs. Bad alternator

The battery provides the power for your vehicle’s engine to start each day. When the battery begins to fail, it is simple to replace. A bad alternator, on the other hand, fails to properly recharge your battery as the car runs. If the alternator fails, it will cost more to repair than a dead battery. The symptoms of a bad alternator are like those of a bad battery, making it difficult to pinpoint the exact problem. Knowing the various warning signs of each going wrong can be beneficial.

Symptoms of a Bad Battery

Almost everyone has had to jump-start a car battery or witnessed someone else do so at some point. Assume you try to start your car in the morning, and it won’t start. Perhaps you left an interior light on all night, causing your battery to die, but it could also indicate that your battery is failing.

According to Matthew Hart, owner of, the following are signs that your battery is failing:

  • It’s difficult to start the car.
  • Once started, the car’s battery does not last long.
  • Taillights and headlights that are dim or flickering.
  • Reduce the brightness of the interior and dashboard lights.

Car batteries typically last three to five years, but other factors can reduce their lifespan. Additional accessories connected to a car battery, such as an internal inverter, can shorten its overall lifespan. If you’re having problems with your car, check the battery. “There may be corrosion around the points on the battery,” says Patrick McCann of This corrosion can be a sign of degradation, but the battery may also require cleaning. If your battery is starting to fail, your vehicle may have a warning light indicator on the dashboard.

Symptoms of a Bad Alternator

The battery in your car is charged, but the alternator works to recharge it while the vehicle is running. That’s why you can drive all day without recharging your battery but leaving the lights on overnight will drain it. If the alternator fails, the battery will no longer be able to recharge while the engine is running.

Here’s how to tell if your alternator is malfunctioning. If the car dies after a jump start, this is one of the most obvious signs. Even if the battery fails, the alternator should provide enough current to keep the vehicle running. If it doesn’t, your alternator should be checked.

“If your alternator is going bad, you might see the voltage meter on your dashboard start to drop, or your car might start to vibrate while you’re driving,” says Matthew Hart. The vibrations are typically caused by misfires within the spark plug caused by a lack of current from the alternator.

According to McCann, another way to tell if you have a bad alternator is to check the battery voltage after charging it. “If the [battery’s] voltage is low, replace it with a new battery or charge it to the recommended 14.2 to 14.7 volts,” he recommends. “Then try to start the vehicle and see if the voltage after that falls outside of that range.” If it is, it indicates a faulty alternator.”

How to Repair a Faulty Battery or Alternator

If your battery dies, you can replace it at almost any auto parts store. Many stores include battery replacement as part of the purchase price. If your know-how, you can also replace it yourself. Conduct research to find the best battery for your requirements. Repairing an alternator may be more expensive than replacing the battery. The price you pay will be determined by the make and model of your vehicle, as well as the cost of parts and labor.

If your battery or alternator fails, you should have your vehicle inspected by a mechanic. While the symptoms of a bad car battery versus an alternator are obvious, they can also indicate other, more subtle mechanical issues.

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