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Why Does My Battery Keep Dying?

Your vehicle battery is designed to provide enough juice to keep all the electronics in your car going when the engine is not running, but the primary purpose of the battery is to power the starter motor that gets the engine running on startup.

Not only is a dead battery frustrating, but it often indicates a repair is imminent. That can mean an unexpected expense of $150 and up to change the battery or something more expensive to diagnose and fix. If you’ve been asking yourself “why does my car battery keep dying”, continue reading for some helpful tips and tricks to maintain your battery.

Car Battery Life

Modern batteries have a typical operational life of between three and five years, but many can last beyond that if you keep them charged and maintain the connections. The older a battery is, the more likely you will begin to see issues with slow startup, or even electrical gremlins with accessories in the vehicle, so it’s wise to replace your vehicle battery before it dies completely.

Can I Test My Own Battery?

The good news is that you can do some quick battery tests in your own home, with some basic tools, that will assess whether the battery is at fault or perhaps you have an issue somewhere else in the vehicle’s electrical system. Follow this guide to do a basic check on your battery.

Complete a visual inspection

Often, mechanics can diagnose a problem simply by looking under the hood. If you see loose wiring, a frayed or severed cable, or even corrosion on the battery terminals, you may have found what drains the car battery. Replace any broken cables or connections, if you can, and clean the battery terminals and cable connections with a wire brush before applying some dielectric grease and reconnecting everything. It is surprising how many battery issues can be solved with a simple cleaning like this.

Test the voltage

testing a battery with a multimeter
Testing your car battery with a multimeter

If that doesn’t solve your problem, use a multimeter to test the voltage on the battery. A multimeter is an electronic tool that can measure voltage and amperage from a variety of sources, so it’s very useful to have around the house. Start by disconnecting the negative cable on the battery. Then set the multimeter to 20V on the direct current (DCV) mode and measure the voltage across the negative and positive battery terminals. If the voltage reading is between 12.4 and 12.6 volts, your battery is charged properly, and any electrical issues lie elsewhere in the system. If the voltage is below 12.4V, charge the battery fully and repeat the test.

Check the charging system

One other possibility is that your alternator is not functioning up to specifications and leaving your battery weak, even after long drives. To test your charging system (the alternator), have a friend start the vehicle and keep the engine RPMs at a steady 2,000. Place your multimeter leads on the positive and negative battery terminals to measure the voltage. If you are seeing between 13.5 and 14.5 volts, then your alternator is doing its job.

Should I Get a Trickle Charger?

Charging a battery with duralst battery charger

A trickle charger is a cheap way to increase the service life of your car battery by keeping it fully charged. In modern cars, there are so many electrical draws that even continue when the vehicle is turned off, so batteries take a beating. If you live in a climate with extreme temperatures, your battery will also live a rough life, so keeping it charged with an intelligent trickle charger is a smart move.

At AutoZone, you’ll find all the parts you need, batteries for all makes and models, and the tools to test them at a great price. If you decide that it’s too big a job to tackle on your own, let AutoZone help you find qualified professional mechanics through our Shop Referral Program

FAQ

What can drain a car battery when the car is off?

Modern vehicles have security systems and all kinds of electronics that continue to run even when the vehicle is off. Add to these draws a potential dash cam that is drawing electricity or even a radio that is left on after the vehicle is off, and you have several different potential draws that can explain why a car battery drains overnight.

Why is my battery dying so fast?

It could be a failing alternator. Get your alternator checked and replace it if needed. 

How do you fix a battery that won’t hold a charge?

Most modern batteries are sealed units that require less maintenance than older batteries but don’t allow for maintenance to be done on them. If you find that your battery is no longer holding a charge you should look into replacing the battery with a new unit and recycle the old battery in the process.

How can I tell if I have a bad alternator?

If you start with a fully charged battery, and the battery loses its charge over a matter of days or less, it’s a good bet that your alternator needs to be replaced, since it’s the alternator’s job to recharge the battery as the vehicle is running.

How do I know if my starter is draining my battery?

If your battery is low, you will notice that the starting cadence of your engine is much slower than usual, and if the battery is almost dead, you’ll hear nothing but a clicking sound coming from the starter.

How do you check for a parasitic battery drain?

With a fully charged battery, use a multimeter to measure the amperage between the negative cable and the negative battery terminal while you remove single fuses from the vehicle fuse block. When you remove the fuse that corresponds with the parasitic battery drain you will notice the amperage draw on the multimeter drop.

Advice, how-to guides, and car care information featured on AutoZone.com 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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