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You hear the dreaded ‘click’ when you attempt to start your car and you instantly know that you’re not getting to your destination when expected. Your battery is dead, and while your immediate mission is to find a Good Samaritan with jumper cables (here is our selection of best booster cables on the market), you also know that you need to get to the root cause of the problem so that you can get to work the next day.
The good news is that battery problems can generally be diagnosed and solved without the aid of an expensive expert mechanic. All that is required is a very basic understanding of two vehicle electrical components and to use that knowledge while observing the vehicle’s behavior.
Diagnose a Dead Car Battery
The first electrical component is the battery. This is a rechargeable battery that is designed to provide energy for starting the engine and for powering accessories such as the head lamps for short periods of time.
The second is the alternator. This component uses the engine power to provide energy for all of your vehicle’s electrical components and to recharge the battery. The alternator is driven by a belt connected to the engine.
Common Battery and Charging System Failures and their Causes
Equipped with this basic knowledge, it is easy to apply it to solving some common vehicle electrical malfunctions. Below are some of the more common battery and charging system failures and their causes.
- When your car battery goes dead, try to determine if you left something on for a long period of time. While the most common error is leaving head lights on, other components like interior lights or components connected to 12 Volt receptacles can be the cause. In most cases, a jump start will get you back on the road. Keep in mind that continued mistakes of this nature will ultimately destroy your battery.
- If your car battery goes dead after leaving lights on for a very short period of time, it will likely need replacement. This is especially true if this occurs after you have been driving a long period of time at higher speeds. Your battery, while able to store enough energy to start your vehicle, no longer has the capacity to power other vehicle devices the way it was intended to.
- If your car runs perfectly after a jump start, but fails to restart after a lengthy drive, suspect your battery. However before you replace your battery, inspect the battery terminals. If they are covered with corrosion, clean them first. Sometimes it will be the electrical connections that fail.
- If your vehicle lights begin dimming while driving, suspect your alternator. This is an indication that your alternator can no longer power the vehicle electrical load. The cause might be the alternator itself or it may be that the alternator belt is loose or broken. Keep in mind that intermittent dimming or loss of electrical power may mean that the alternator, while not completely broken, is beginning to fail.
- Alternators generally deliver more energy at higher speeds. More, it takes some time for an alternator to fully charge a battery. Thus if you drive short distances in stop and go traffic, your alternator may never fully charge your battery. Continued vehicle operation in this way may cause your battery to go dead and give the appearance of requiring replacement while in fact being perfectly good.
- Occasionally a bad alternator will destroy your battery. Alternators include regulating circuits that keep the voltage from going too high. Charging a battery at a voltage that is too high will damage it. You can measure the output of the alternator at the battery terminals. With a fully charged battery and the engine running, the voltage will generally be between 13.5 and 14.5 Volts.
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Some of the links in this post are affiliate links. As an Amazon Associate, we earn from qualifying purchases. This means if you click on the link and purchase the item, we may receive an affiliate commission, at no extra cost to you. This helps us keep this website alive. Learn more here.