One of the things that car owners dread is finding out that they cannot start their vehicles when they are rushing for an appointment. While there can be a host of issues as to why the engine doesn’t want to turn over, one of the most common culprits is a dead battery. This often-overlooked part of a modern vehicle starts the system that runs the engine as well as the electrical components of the car. With the battery dead, it would be almost impossible to start the car. But why did the battery die anyway? Here are 8 answers to the question, what can drain a car battery when it’s off?

Human Oversight

Regardless of how religious you are in your post-drive car checks, there will always be instances when you forget something. You may leave the headlight on or fail to close the trunk completely. You may also forget to switch off the dome light in the passenger cabin the moment you stepped out of your car. These things are examples of human oversight. The problem is that these “events” are also utilizing electricity from the battery. The car battery dies overnight because these “electrical” components are running all night long. While some modern vehicles now have alerts to warn the vehicle owner if something is still left on, older vehicles may not be so lucky.

Defective or Faulty Charging System

Whenever you’re driving, the electrical components of your car derive their power from the alternator. At the same time, this piece of automotive equipment is responsible for charging the battery. If there is a problem in this battery charging system, you can also experience battery drain. It is possible that the problem is not in the alternator itself, but the other components that run it. For instance, worn-out belt tensioners or loose belts can keep the alternator from functioning in an optimal manner. Hence, if your car battery keeps dying even while driving it, then there must be an issue in your vehicle’s charging system.

Farista Shop_Corroded Battery Cables

Corroded Battery Cables

Electrical Problems

Mechanics call it the parasitic drain. However, one has to understand that parasitic drain is a normal occurrence. There are some car components that have to run 24/7. For example, your car’s security system has to be on round-the-clock. If not, then how do you expect it to perform its security duties? Other examples are radio presets and vehicle clock. These devices rely on power from your battery to keep them operating. The real issue is when you have defective fuses, faulty wirings, or faulty installation of electrical components. These “trouble spots” can be the source of why a car battery dies overnight.

Bad Alternator Diode

As mentioned, the alternator is a critical piece of car technology that performs two basic things. It powers up the car’s electronics during vehicle operation and it also recharges the battery. In instances where the diode in the alternator has gone bad, then it keeps on charging the system though the engine is already shut off. When you start the engine in the morning, you will not be able to since you already have a discharged car battery. Other issues with the alternator can also lead to insufficient charging of the power cells.

Excessive Short Drives

This is related to the second function of the alternator: recharging the battery. Know that it takes time for the alternator to pump up the juice into your car’s power cells. And the only way you can keep the alternator running is by taking the vehicle on longer drives. But if you’re the type of motorist who uses his vehicle for only 5 to 10 minutes or for short distances, then you’ve found one possible reason for a car battery drain. If you turn off the engine before the alternator can recharge the battery, then the power cells will keep on draining.

Temperature Extremes

Extremes in temperature can also favor the buildup of lead sulfate crystals. This can lead to longer battery charging times, ultra-short battery life, and battery failure. Sulfation in batteries can impair the effective conversion of chemical energy into electrical energy. Because the battery will take a much longer time to reach full charge, it may not be 100% recharged by the time you turn off the engine. And if you take your car for very short drives, then you’ve found the culprit as to why the car battery keeps dying.

Farista Shop_Bad Alternator Diode

Bad Alternator Diode

Loose or Corroded Battery Cables

Corrosion can also be a major reason for your vehicle’s power cells not keeping their charge. Rust has a way of affecting the composition of the chemicals involved in the conversion of chemical energy into an electrical one. In other words, corrosion can prevent your battery from getting 100% recharged. It is best to check the integrity of your cables. If you see any sign of corrosion, then you should clean it up as soon as possible. As for loose battery cables, the problem here will be difficulty in starting your engine. This is very easy to fix, though.

Old or Weak Battery

Everything has an expiration. Even with the latest advances in car battery technology, we have yet to find a system that will last a hundred or so years. The reason is simple. The passage of time brings with it factors that can undermine the durability of these devices. For us humans, we call it aging. For non-living things, we call it normal wear. Most batteries come with a lifespan of about 3 to 4 years. However, this figure has its basis on normal driving conditions. Without the correct maintenance and with poor driving habits, don’t expect the battery’s lifespan to be that long.

Your car’s battery may still be in good working order. However, your knowledge of what can drain a car battery when it’s off can help you institute preventive measures. This should save you from the dread of not being able to start your car when you need it most.

Sources:

The Top 8 Things that Will Drain Your Car Battery – Your Mechanic

Why Does My Car Battery Keep Dying – Lifewire

CarBibles