Advice

Is My Car Battery Dead?

By 11/29/2023 8:00am

Corrosion on car battery terminals

Quick Facts About Car Batteries

A car battery usually isn’t on a driver’s mind until it’s a dead battery. And, like those in your flashlight, failing car batteries are never convenient. However, the battery in your vehicle may show warning signs of its demise. Read on to learn about the symptoms of dying car batteries and how to deal with a dead battery.

Car batteries are essential to starting vehicles and supplying power to assorted accessories when the ignition is off. We’ll give you maintenance tips, advice on choosing a replacement, and how much you can expect to pay for a new battery. And without getting too deep into the weeds, our car battery overview explains how they work.

Let’s get into it.

Signs Your Car’s Battery Is Dying

A failing battery’s symptoms might be attributed to problems with other components, such as the starter, alternator, or other electrical parts. However, for our purposes here, we will assume all the listed symptoms are battery-related.

Although a new battery failing is not unheard of, the older your battery, the more likely one of our warning signs below indicates it is failing or dead. Signs include the engine won’t crank, or it’s slow to start. Read on for more.

1. Illuminated Battery Warning Light

Unsurprisingly, you have a battery-related issue if the battery warning light in your gauge cluster illuminates. It may not be a complete battery failure, but whatever the problem is, it will probably eventually impact battery efficiency or life.

2. Engine Won’t Crank

You turn the ignition key, and nothing happens. Or maybe you hear a clicking sound. The engine not cranking is a signal that either your battery is already dead or there is very little power left in it.

3. The Engine Is Slow to Crank

Hearing a low moan or a series of moans when you turn the ignition key — even if the engine eventually starts — might indicate you have a dying battery.

4. The Engine Starts But Immediately Dies

As a battery fails, it may have enough juice to start the engine but not enough to keep it idling for a few seconds until the electric system fully functions.

5. No Dome Light

Unless you’ve turned off the function or the fuse is blown, if you open a car door and the interior lights don’t illuminate, that’s a sign of a failed or failing battery.

6. Dark, Dim, or Flickering Headlights

Your car’s headlights losing their brightness, flickering, or not illuminating at all are issues that point to battery failure. The likelihood of battery trouble is stronger when dim lights happen with one or more of our other warning signs.

7. Signs of Fluid Leakage

Evidence that your car’s battery is leaking or previously leaked (such as dried fluid on the battery or in the battery tray) indicates something amiss with its operation and structural integrity.

8. Battery Box Integrity

If the battery’s structure is swollen or cracked, it’s time to replace the battery.

What Causes a Dead Car Battery?

There are plenty of signs of a dead car battery. However, a top cause is the age of the car battery. Other causes include extreme temperatures, corrosion, leaving lights on inside or out, a bad alternator, and more.

What To Do if Your Car’s Battery Dies

How to jump start a dead car battery.

When faced with a car that won’t start, the first thing to do is pop the hood and check for a dead battery. You may be lucky and find the issue is a loose or dirty connection at one of the terminals. If so, correct the problem and try starting the engine again.

If a terminal connection isn’t the answer, you will need to start your car with another process — this typically means jump-starting it using the battery in another vehicle or a portable jump-starter. Again, you may be lucky if your vehicle is still under warranty with a roadside assistance feature. Getting your car started should be among the covered services. Some car insurance policies also include roadside assistance. If you belong to a car club like AAA, roadside assistance is a covered service.

Take Action

Otherwise, you must jump-start the vehicle yourself. You should keep a set of good-quality jumper cables in your car (and know how to use them). You’ll also need to call a friend or flag down a friendly motorist willing to help you jump your car using their battery. A portable jump-starter can be another solution and is a handy device to keep in your vehicle.

The bad news is that the alternator responsible for keeping your battery charged while the engine is running isn’t engineered to charge a completely dead battery. However, once you have successfully jump-started the vehicle, drive it around for 20 minutes or more to ensure the battery is charged.

Unless you know the battery died because of accidentally leaving the headlights on overnight, you should have the car battery tested as soon as possible. Any repair shop, dealer service center, and many auto parts stores can test the battery. If such a test reveals that the battery is failing, replace it. A weak battery wreaks havoc on other electric components, including the vehicle’s alternator.

How To Choose a Replacement Car Battery

One size fits all doesn’t even always work with baseball caps, and there certainly isn’t a single solution for a replacement car battery. A battery needs to be the appropriate size to function efficiently, have sufficient cranking power, and have the terminals in the correct position for your car.

5 Things To Consider

  • Battery group size – This refers to the battery class that will best fit the physical dimensions of your vehicle, including the terminal location. Your car’s year, make, and model requires a specific battery group size. Usually, the larger the size, the higher the level of starting power. You can find the group size on the battery you are replacing or in your car’s owner’s manual. They look like 24, 24F, 27, 34, and so on.
  • Reserve capacity – This is a measurement of the actual time a car battery can power essential accessories on its own. Why is that important? It tells you how long that battery can keep devices operating and so forth once the engine stops running. The figure also indicates how long the power will last if the alternator dies.
  • Cranking amperage – In battery terms, cranking amps are basically a cold weather measure. It’s the number of amperes (a base unit of electric current) a battery can deliver for 30 seconds at 32 degrees Fahrenheit. You will also hear the term “cold cranking amps,” which sounds redundant but isn’t. This is a separate rating for the number of amperes a battery can deliver for 30 seconds in a zero-degree temperature. The second measure is crucial if you live in the Snow Belt.
  • Freshness date – We don’t think much about a new battery’s freshness as we do for a gallon of milk. Still, the more recent a battery’s manufacture date, the more distant its “best by” date would be — if they had them. Six months probably won’t make much difference in the greater scheme of things, but a year or more could.
  • Warranty – Batteries fail. Some fail sooner than others. As with anything else, there’s no certainty regarding longevity. When purchasing a new car battery, buying one with a warranty spanning at least two years is best. Several battery manufacturers have warranty coverage for more extended periods. For example, Interstate Super Premium and DieHard Platinum batteries have 48-month free-replacement warranties.

How Much Do Car Replacement Batteries Cost?

With so many aspects to weigh, zeroing in on an average price for a new battery won’t tell you much. Moreover, when it’s time to replace a battery, you have little choice but to buy one, right? You can then choose to skimp (a relative term) or go big.

We searched the websites of several major car parts stores and found conventional batteries for as little as $45 to more than $250. We recommend you budget at least $200 for a conventional battery replacement.

An absorbed glass mat or AGM battery (discussed below) uses newer technology and costs more. You should budget at least $300 for an AGM replacement battery.

How To Extend Your Car Battery’s Life

It’s worth repeating: Every battery will eventually die. That death may be permanent or, in some cases, temporary. In many respects, there isn’t much you can do to prolong the inevitable. However, you can take a few precautions, like ensuring all the interior and exterior lights are off when you exit the vehicle. Newer vehicles may have exterior lights that turn off automatically, but manually controlled systems leave this task for you. Even an interior map light left on overnight can drain an older battery.

In colder climates, a battery blanket is a must-have accessory. Freezing temperatures sap a battery’s power and can even damage it. Insulated battery blankets and heated electric blankets can prevent the cold from draining power.

Performing some battery maintenance as part of routine car maintenance can also forestall issues down the road. Ensuring the terminals are clean and corrosion-free is a good starting point. If the battery has fill ports, checking the fluid levels and topping them off with distilled water helps prevent lead plate corrosion.

What Shortens a Conventional Car Battery’s Life?

A conventional car battery’s multi-plate design allows for the shaking and vibrating of plates as the car drives along the road. All that jostling of the plates and sloshing of the electrolyte solution creates wear and tear.

Moreover, the electrolyte solution can leak out of the battery or boil out if the alternator malfunctions and overcharges the battery. Reduced levels of the battery solution can expose the lead plates, leading to corrosion and reduced battery efficiency.

Extreme temperatures can also shorten a battery’s life and performance.

Conventional Batteries vs. Absorbed Glass Mat Batteries

AGM batteries use a bit of technology from the aerospace industry. They are more compact and lighter than conventional car batteries and are literally maintenance-free. Although they still use lead plates surrounded by an electrolyte solution, a glass-mat separator is between the lead plates. These fiberglass mats attract the electrolytes and store them in a dry state. As the need arises, the electrolytes transfer to the lead plates to create a charge.

Because of the glass-mat construction, AGM batteries discharge slower than conventional ones. In other words, they retain their charge longer. This makes them ideal for today’s highly technological vehicles with many devices and electronics. AGM batteries also recharge more quickly than conventional batteries. Furthermore, because of the tighter packing of the battery elements, there is much less vibration than in conventional batteries. This design reduces wear and tear.

The average AGM battery costs more, is more efficient, requires less maintenance, holds more charge longer, and will outlive a conventional battery by two to three years.

How Does a Car Battery Work?

The way a conventional battery works is relatively simple. In fact, it’s so simple that the basic principle of an electric storage battery has remained unchanged since a French physicist invented it more than 160 years ago.

The Anatomy of a Conventional Car Battery

All car batteries use lead-acid technology, as they have since 1859. Today, some conventional batteries provide removable caps for adding distilled water. Others are “closed” and don’t require adding water.

In either case, they are composed of a series of lead plates alternating with plates of other materials. Surrounding the plates is an electrolyte solution of sulfuric acid and water. Engaging the ignition causes the electrolyte solution to react to the lead plates. Such a reaction discharges sufficient electric current to start the car.

How a Car Battery Recharges

Although a reaction within the battery provides an extra burst of electric power to start the engine, a battery merely stores electric energy. An alternator is key to recharging and maintaining a battery’s charge.

Once the engine runs, the alternator siphons off some of the engine output via a belt and pully. Thus transforming mechanical energy into electrical energy. It then transfers that electric energy to the battery to recharge it.

A healthy new battery can repeat the discharging-charging process tens of thousands of times. However, it will eventually lose its capacity to recharge. Therefore a conventional battery will fail in three to five years under average conditions.

Here’s the catch: A conventional battery’s core efficiency lies in starting the engine. It will produce a trickle current to keep the headlights, radio, and so forth running for a limited period after the engine disengages. However, the battery is not engineered for that. Therefore, whatever charge rapidly runs out in the battery when the engine stops, just like the battery in your flashlight.

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