When your car battery dies once, it can be tempting to simply write it off as an accident. Batteries may fail for a variety of reasons. and there’s always a chance that whatever went wrong won’t hurt again. But when your car battery keeps draining over and over again, it’s likely that there’s an underlying problem that needs to be addressed before you end up stuck somewhere.

An illustration of six reasons why a car battery is constantly dying

Why do car batteries die?

The list of problems that can lead to a dead car battery is so long that it is close to endless, but almost everyone battery killer can be divided into three main categories: battery problems, electrical system problems, and simple user error. Some of these can be dealt with at home, and others will likely require a visit to your mechanic, but it’s impossible to know for sure until you roll up your sleeves and dig around.

It’s also important to note that when most people talk about a battery dying all the time, they’re talking about a situation where the vehicle won’t start after it’s been parked for any amount of time. If your battery is draining while you’re driving on the road, it’s more likely that you have some kind of problem with the charging system (we’ll also look at this situation).

What causes a car battery to keep dying?

Some of the most common causes of frequent car battery drain include loose or corroded battery connections, constant electrical discharges, charging problems, constantly requiring more power than the generator can provide and even extreme weather conditions. Some of these problems are enough to kill the battery on their own, while others are usually related to an already dead battery or its last legs.

  1. Headlights or dome lights remain on.
    1. Headlights, or even a very dim dome light, will drain the battery overnight.
    2. Be sure to check for indoor lighting when it’s dark outside.
    3. Some headlights are designed to last for a while, but a faulty system can leave them on forever.
  2. The battery is weak or in poor condition.
    1. A poorly maintained or weak battery may not hold a charge well.
    2. Even a small leak, such as your car radio’s memory function, can kill a very weak battery.
  3. Corrosion or loss of battery connection.
    1. Corroded battery connections can prevent the system from charging the battery while driving.
    2. Loose battery connections can also cause problems.
  4. Other parasitic drains in the electrical system.
    1. It can be difficult to find parasitic drains, but they are fully capable of killing dead batteries.
    2. Common drains include the glove box and trunk light, which turn on or stay on when they shouldn’t.
  5. Extremely hot or cold temperatures.
    1. Hot or cold weather will not kill a battery that is new or in good shape, but a weak or old battery can fail under extreme conditions.
    2. Extremely hot or cold weather can also exacerbate other underlying problems.
  6. Problems with system charging.
    1. If the battery drains while driving, the charging system may be faulty.
    2. Loose or tight belts and worn tensioners can interfere with generator operation.

Checking headlights, dome lights and other accessories

Car batteries are designed to power headlights, dome lights, and various other accessories when the engine is off, but their capacity for this is very limited. This means that if there is anything left after the engine is turned off, the battery will almost certainly die.

Leaving the headlights on can waste a weak battery in the time it takes you to do short jobs like grocery shopping, but even a small interior dome light can drain the battery overnight. So if you’re dealing with a battery that runs out over and over again, it’s worth checking it out at night when it’s getting dark, when a weak or dim dome light would be easier to spot.

Some new cars are also meant to be left turned on for a while lights dome lights, or even the radio after you turn off the engine and remove the keys. When everything is working properly, you can walk away from the vehicle like this and everything will turn off on a timer. If you come back half an hour or an hour later and things like headlights are still on, your battery is probably dying.

Servicing and testing a car battery

An auto mechanic diagnoses a car engine.

If you don’t see anything obvious, like headlights or dome lights on, then the next thing to check is the battery itself. Many battery problems can be fixed with basic maintenance and a poorly maintained battery won’t hold a charge like it did when it was new.

If your battery isn’t sealed, it’s important to make sure each cell is properly filled with electrolyte . If you look inside the elements and see that the electrolyte level has dropped below the top of the lead plates This is problem.

The battery cells should be filled with distilled water, but it’s usually okay to go to the faucet, depending on the quality of the water you live in. You can also test your battery with an inexpensive tool called a hydrometer, which allows you to check the specific gravity of the electrolyte in each cell. If one or more cells are empty after the battery is fully charged, the battery needs to be replaced.

Another way to test your battery is to use a more expensive tool called a load tester. This tool creates a load on the battery that simulates a starter pull and allows you to see the voltage of a charged and discharged battery. Some stores and parts stores will test your battery for free if you don’t have a load tester, while others charge a nominal fee.

If you decide to choose your own load tester, it is important to remember that batteries that are internally shorted can explode under the right conditions . That’s why it’s so important to wear protective gear when running on battery power.

Check for loose or corroded car battery connections

When visually inspecting your battery, you may notice corrosion around the battery terminals, cables, or connectors. In some situations, corrosion may not even be noticeable, or you may see large white, blue, or green patches of corrosive material.

If there is any corrosion between the battery terminals and the cable connectors, this will affect the ability of the starter motor to draw current from the battery and the ability of the charging system to charge the battery.

Elimination of corrosion from battery connections and cables

Corrosion on a car battery terminal
Jorge Villalba/Getty Images

Battery corrosion can be cleaned with baking soda, water and a stiff brush. However, it is extremely important to avoid getting baking soda inside the battery cells. It’s also important to note that if you let the baking soda/corrosion mixture stay on the surface of your driveway or on your garage floor, you may end up with a stain that is difficult or impossible to remove.

Corrosion can also be removed from battery terminals and cable connectors with sandpaper or a special tool. These tools are usually in the form of wire brushes which are very easy to use. After using one of these tools, the battery terminals will look bright and clean and you will get a much better electrical connection.

It is also very important that the battery connections are tight. If you find that the battery cables are loose, there’s a good chance you’ve found most of your problem.

If you can ensure that your ground and power battery cables connect to the frame, starter and junction box or fuse box, you should also make sure that these connections are secure and not subject to corrosion.

Check for parasitic drain

If your car battery keeps draining over and over again, one of the simplest explanations is that there is some sort of discharge in the system that persists after you remove the keys and close the doors. Even if you’ve already ruled out obvious things like headlights and dome lights, there could still be a leak in your system.

The easiest way to check for a discharge is to disconnect the battery cable and check the current. If you are using a multimeter for this purpose, it is very important to use the highest amperage setting possible. Otherwise, you risk blowing an expensive fuse inside your meter. Some meters also include an inductive clamp that can test current without shutting it off.

You can also check the drain with a test light, which is less accurate. This is done in the same way by disconnecting the negative battery cable and completing the circuit between the negative battery terminal and ground. If the control lamp lights up, then there is some type of drain in the system.

The problem with using a test lamp is that it is very difficult to determine how much of the drain is present from the brightness of the light alone.

Some of the most common causes of a parasitic drain include trunk, glove compartment, and other lights that are on due to some type of malfunction. These and other indoor lights are designed to turn off automatically, and if they don’t, they can completely drain the battery overnight.

In most cases, the only way to track down a parasitic leak is through a cleanup process. The easiest way to diagnose this type is to connect a multimeter or test light and remove the individual fuses until the leak is gone. You will then need to identify the appropriate circuitry to help you track down the specific component that is causing the problem.

Dealing with extreme weather, charging system problems and weak batteries

Extremely hot or cold weather can also cause problems for your battery but this will usually be a problem if the battery is already dead. If you check the battery and it’s fine and the connections are solid and clean, then the weather shouldn’t cause it to die multiple times.

Issues with the charging system can also cause the battery to drain repeatedly, although you’ll usually notice some handling issues as well. The easiest thing you can check at home is the alternator belt, which should be relatively tight and free of cracks. If the belt seems to be loose, it may actually prevent the alternator from generating enough power to charge the battery in addition to everything else.

What to do if your battery dies while driving?

If your battery seems to keep draining while you are actually driving, the root problem is probably not the battery. The purpose of a car battery is to power the starter motor and provide electricity to run accessories such as headlights and radios when the engine is off. When the engine is running, the charging system takes over. So if the battery seems to die while the engine is running, the problem might be with your charging system.

As mentioned earlier, the only part of the charging system that you can really check or test without special equipment is the strap. If your alternator belt is loose, you can tighten it. You may also have an auto-tensioner belt, in which case this can be a problem. Straps can also stretch with age.

The problem with checking the charging system at home

If you have an inductive clamp multimeter, you can technically check the output power of a generator, but this type of diagnostic is difficult without more specialized tools and a generator-specific knowledge base. For example, trying to test the alternator by disconnecting the battery cable while the engine is running is not a good idea if you drive a modern car.

Some parts stores and repair shops will test your alternator for free, while others will want to charge you for diagnostics. However, it is important to note that there is a difference between a simple test and an in-depth diagnosis that actually helps to understand the cause of the problem.

In most cases when generator not charging and the engine does die, it’s just a case of a bad alternator that needs to be repaired or replaced. However, there are actually several reasons why the vehicle’s electrical system may shut down while driving and even more reasons why the engine just dies.

How to protect the battery from multiple deaths

While it is true that every single battery must eventually run out, the key to extending battery life is a lead acid battery like the one in your car, is to keep it in good condition and serviceable condition. If you are facing a situation where your battery is being drained over and over again, there is a good chance that every time it dies, the terminal life of the battery is shortened.

By maintaining a top layer of corrosion, making sure the battery connections are tight and secure, and keeping the electrolyte from falling into an unsealed battery, you really you can extend the term services batteries .

There is little you can do to avoid other problems such as a sudden parasitic drain, but addressing this problem in a timely manner can also help extend the life of your battery. The battery can also help in the winter if it’s especially cold outside or if you don’t plan on driving for an extended period of time.

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