Signs Of A Bad Car Battery vs. Alternator

Cars are interesting machines and worth owning. However, they can fail and require maintenance and repair. Sometimes, certain parts or components of your car may fail, and you will not know. In other cases, you may end up diagnosing the wrong problem.

A component that will bring many effects to your car in case of failure is your car battery and alternator. However, you need to understand exactly what happens when your car battery or the alternator goes bad. That will allow you to find the right solution at the right time. Here is all you need to know.

Common signs of a bad car battery vs. bad alternator

Signs of a Bad Car Battery

1. Corrosion on battery terminals

Look at your car battery terminals and examine them carefully. If you find a blueish green powder, then it is a clear sign the battery is going bad. This will mostly happen when the battery lifespan has shortened. Current will not be supplied effectively.

2.    Battery smells like rotten eggs

Normally, your car battery should be normal without any weird smells. However, when your battery goes bad, it starts leaking acid. As the acid leaks from the battery, hydrogen sulfide gas is also produced which comes and the battery smells like rotten eggs.

3.    Old battery

Car batteries also grow old. All car batteries have a lifespan, after which they become old their performance deteriorates slowly with time. Car batteries have an average lifespan of 4 to 6 years. If the battery has reached this age, it is a sign.

4.    Slow crank

A slow crank is when the engine takes a long time to fire up when you put the ignition switch on. For cars with a dead battery, it does not matter the weather or the state of the car. If the car engine is still warm and it struggles to crank, then the battery is bad.

5.    Car won’t start when turning the key

When you turn your car’s ignition key on, the car should start immediately. However, when you turn the ignition key on, car won’t start, no noise, then it is a sign of a bad battery. If there is no sound or any response, it means that the battery is actually dead.

6.    Dim headlights

Your car battery is responsible for powering the headlights. As long as there is power in the battery or the car is running, then the headlights will be bright. However, if the headlights are dim, it means the battery is not able to produce enough power even with the engine on, and it is bad.

Signs of an Alternator

1.    Odd Sounds

A car alternator is a device whose work is to turn the engine motion into electric power and store it in your battery. The alternator is connected to the engine using a belt. So, when the alternator is faulty, one of the areas affected is the belt.

When you hear some odd sounds coming from your hood, it is a result of alternator belt problems. This is when the belt rubs against other parts of the car. The odd sounds may also be coming from the inner components of the alternator if they are broken. You should check immediately.

2.    Smell of burning rubber

For the alternator to work, it is connected to several belt systems. One of the things that can lead to a bad alternator is broken or malfunctioning belts. So, when any of the belts do not move freely or have an obstacle, there will be friction.

The alternator belts run very fast. With time, the belt will start burning up and produce a rubber smell. In most cases, this happens when a belt slips off an alternator pulley.

3.    Dead battery

When your battery is dead and does not produce any power, it is a sign there is an issue with your alternator. Your car alternator should be able to charge your car battery at all times the car is running. So, when the alternator is not working, or bad, the battery will not get any power. Once all the power in the battery is used up, it will die.

4.    Dashboard warning lights

If your alternator is failing or has already gone bad, you will get warning lights on your dashboard. In most cases, you will get battery warning lights showing that there is a problem with the battery power system.

These warning lights are provided because the alternator feeds power directly to the engine. So, if the alternator is not able to provide this power, you will get warning lights. The alternator is also designed to operate at specific voltage levels of 13 to 14.5 volts, and when that changes, you will get a warning light on your car dashboard.

5.    Starting problem

This is a very simple sign to understand. You will experience a hard start, or your car will not start at all when you turn the ignition.

This means that there is no power on your car battery. Your car battery could be in good condition, but the alternator has not been working to charge it. Even after running the car for a long-distance, you will experience this problem.

6.    Dim headlights

Dim headlights are a clear sign that your alternator is bad. That is provided the car battery is good. Remember that the alternator is supposed to provide power to the battery and, in some cases, directly to other car components.

So, when the alternator fails, it means that the alternator is not able to supply consistent high power levels to light the headlights. In some, the light may keep on flickering, indicating the alternator is supplying inconsistent power levels.

How Do You Know if your Car Battery or Alternator is Bad?

A bad car battery or bad alternator is some of the serious car electrical problems you may experience. As a result, you should diagnose your car correctly to find out which problem it is. Most of the signs of a bad car battery and alternator are similar, however, there are some ways for you to tell the differences and know which one is bad. Here are the tips to follow.

  1. Start your car and let the engine keep running for about 10 minutes. This will alternator enough time to fully charge the battery. Here are two actions to take.
  • Disconnect the negative battery terminal while the car engine is running. If your car engine stops immediately, it is a sign of a bad alternator.
  • If the car engine stays running, it means you have a bad car battery that cannot support charge enough to crank the engine.
  1. For this second way, you will have to use tools to check your alternator voltage output when the car is running. Start by getting a voltmeter and setting it to a 2- a digit range or 12 volts. Place the red probe on your positive battery terminal and the black on the negative. You should get a reading between 13 and 14 volts indicating the battery is charging. If you get below or above this, then the alternator is bad.

Can a Bad Alternator Ruin a Car Battery?

Yes, a bad car alternator can definitely ruin a car battery. However, a bad car battery can also ruin the alternator as well. This happens when the battery fails and forces the alternator to overwork.

Here is how a bad car alternator can ruin a battery.

  1. It will produce ripple voltage. Ripple voltage is AC moving through the alternator’s rectifier and converted to DC. So, when any alternator’s rectifier faults, maybe from a diode shorting out, AC current will reach the battery instead of DC. This AC ripple current is dangerous and can easily kill your battery and other car electronics.
  2. The alternator will produce insufficient or no charge. This will not charge the battery enough hence making it run flat and end up poisoning a lead-acid battery.
  3. A faulty alternator can easily damage its voltage regulator hence leading to the output of the alternator defaulting to maximum, and this means that the battery is now being overcharged. In this case, the battery will get very hot, and the electrolyte can boil off. When this happens, the battery electrode plate will distort and buckle and finally destroy the battery.

Last Words

Many car owners will suffer the problem of a bad alternator or car battery and will not be able to tell the difference. If you cannot tell the difference, when one of them spoils, it will end up spoiling the other if not addressed early enough. As a result, make sure to regularly inspect your car’s charging system, and take proper care of your car battery — it will be all worth it in the long run.