Car Battery Dead? 8 Signs of a Dead Car Battery

Not all batteries will give you warning signs that failure is coming, but sometimes they do. While a “dead” battery is often defined as a battery that simply cannot start the car, Below are several things that could indicate a bad battery, and if you see them, you can always visit an AutoZone store for a free battery and charging system test.

Signs of a dead car battery

1. A Sudden, Slower Start

When temps drop below 20 degrees, generally any car’s starting cadence will slow down. Get below 0 and it gets even slower. If you notice this behavior suddenly and the temperature hasn’t dropped – a slow, dragging start suddenly begin, get your battery tested as soon as possible and don’t ignore it. Eventually, the car will not start.

If a slow starting battery seems to be able to take a charge and test fine, it’s likely that a parasitic drain, or draw is discharging the battery while the vehicle sits, and the electrical system will need to be looked at.

2. Headlights and Power, But No Start

Your lights work, the radio works, but you get a click or buzz once you hit the key. Or, your headlights are very dim. The purpose of the battery is to crank the engine by providing a full dose of high-amperage power to the starter. When the battery is low, it cannot deliver that power but often can still supply enough power for lights or accessories, that don’t require as much amperage.

Keep in mind, jump-starting the car in these situations should only be done in an emergency. Get the battery tested as soon as possible, and do not rely on the alternator to charge the battery back up!

3. No radio

Your radio doesn’t turn on. Don’t mistake it for a minor inconvenience. When the ignition is in the ON position, the battery will run the radio, windshield wipers, and headlights, among other electronic devices. If these flicker or dim before starting, your battery charge is weak.

4. Swollen battery size

The battery is fat, or swollen. The manufacturer designs your battery to have a specific footprint, and if the battery swells in size, you should be able to see it. If you have a bloated battery, the alternator has a faulty voltage regulator and has over charged the battery. This over charging of the battery is caused by a buildup of hydrogen gases faster than the battery can dissipate. Damage to the battery has already been done and cannot be reversed.

5. Odd smell from your battery

If the battery smells – This is a warning sign that your battery is ready to fail, if it hasn’t already. Usually, a battery has no smell, by design. If you smell rotten eggs, this means that your battery has vented gas. It has also released sulfuric acid that could harm other parts of your engine. So this smell is potentially the costliest problem listed here if you aren’t proactive in fixing it. AutoZone recommends replacing the battery quickly.

6. Your battery is old

Your battery is old. The average life span of a car battery is typically between four to six years. At around the four-year mark, you should pay more attention to it. Have a technician check to see how much charge it has. AutoZone provides this service for free.

7. Check engine light flashes

The check engine light flashes or stays on constantly. Generally, this light identifies serious problems in your engine that will require costly maintenance. But you may get lucky and discover that it’s only your car battery that needs replacement. Visit your local AutoZone store for a free diagnosis.

8. Vehicle Starts, Then Dies Immediately

This is a very strange issue that can indeed happen on certain makes / models of vehicles. The battery will have enough voltage to start the vehicle, but then it immediately dies and will not idle. If you encounter this issue, there are a multitude of things that could be wrong, but doing a simple battery check is the first and easiest place to start. The basis behind this is when a battery fails, it can cause interruptions to the constant signals it sends to the ECU. Then if the battery can muster enough might to start the car, the sensors controlling engine idle, speed, and fueling have already lost signal, and the car immediately dies.

If you’re having car battery trouble, it’s time to head to your local AutoZone for free battery testing. If the battery is discharged but still technically sound, we can charge up the battery so you can be on your way. If the battery fails the test, we can help you find a suitable replacement.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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