Your Car Battery Keeps Dying? Here’s the Entire Reason And What Can You Do

Has it ever happened to you to wake up to go to work, get in your car, turn the key to start the engine and nothing happens? No cranking sound, no lights in the dashboard, no radio, nothing. Well, you most certainly have yourself a dead battery case.

A dead battery is not an unusual thing. All types of batteries have a finite lifespan and will die at some point in the future. Just like brake pads and other suspension parts, batteries have to be replaced on a more or less regular basis. Some batteries will last longer than others depending on how they are built, the intended uses they are designed for and the quality of the materials used by the manufacturers but, sure enough, they will all die one day.

But, what if you own a very recent car with a brand new OEM battery and it’s dying on you every other morning for no apparent reason? What if you just replaced your old battery and you still have to jump-start it everytime you want to drive your car? Why does your new car battery keep dying over and over again and what can you do to prevent that?

How does a car battery work?

First, to understand why your battery doesn’t stay fully charged overnight even if it’s new or pretty recent, you need to understand how car batteries are made.

how does a car battery work

To keep it simple, a car battery is typically made of 6 cells containing an anode and a cathode immersed in an electrolyte. The chemical reaction they produce releases electrons, thus creating electricity.

The battery supplies the current needed to make the starter turn. Once the engine is running, the alternator begins to do its job and recharges the battery to keep it full and ready for the next start. All 3 elements of the car battery need to be kept in top shape to produce enough current to power up the starter fast enough to fire up the engine.

What are the main causes of a dying battery?

A number of events can cause the inner workings of a battery to prematurely deteriorate, inevitably leading to a battery failure. Some of these events are directly related to honest human errors, others are caused by electrical failures or defective parts, and some are simply due to variables completely out of your control.

Leaving the exterior lights on

This one is pretty much self-explanatory but it needed to be included here because it’s something that probably happened to everybody at least once. This is not rocket science and everyone can easily understand that leaving the headlights on for the whole night will eventually drain the battery completely dry and your car won’t start in the morning.

If your battery keeps dying and you double-checked your headlights and you are absolutely sure you did not leave them on last time you used your vehicle, be aware that newer cars are sometimes equipped with automatic headlights. You know, the type of headlights staying on when you leave the car and eventually shut down automatically after a minute or so? Well, this type of lighting system can sometimes fail to shut down and keep the lights on for no apparent reason. Always make sure this is not the case before rushing to go buy a new battery.

It’s worth mentioning that newer vehicles equipped with a keyless entry system or proximity sensors can also trick the car and make it “think” that you are close to the vehicle wrongfully and consequently trigger the lighting system and other electrical systems in the vehicle, drawing current all night long without you knowing.

Using the vehicle only for short distances

As said earlier, every time you start your vehicle, the starter uses some of the current available stored in the battery. The alternator then has to work hard to refill the battery with current. But the alternator also has to power up every electrical components used in the car while driving. Especially in winter, when you’re driving with the heater blower at full blast, the rear defrost, heating seats, and heated mirrors on for the whole trip, the alternator may have a hard time barely providing enough current to power everything up. If you only drive your car on short trips to the corner store, leave the car parked for days and drive it again to go the post office regularly, the alternator may not be able to fully recharge the battery every time, leading to a weaker and weaker battery and to an inevitable no crank condition.

If this is your case, the best advice I can give you is to take your car for a long drive every once in a while. Driving for 30-40km once a week should be enough to keep your battery in a good working condition.

Faulty charging system

check charging system

A bad charging system may also be the cause of a dying battery if no human interaction is to blame. The alternator’s job is to power all the electrical accessories and to charge back the battery after starting the engine at the same time. If the alternator goes bad, the electrical system will feed itself from the battery and will drain it until the car stalls.

Sometimes, an intermittent electrical problem can cause the alternator to go on and off. In such a situation, the alternator can provide just enough current to power the electrical system but not enough to charge the battery. Most of the times, the car will not stall and will be able to reach its final destination but the starter won’t have enough power to start the engine the next day.

Sadly, there’s not much you can do to prevent that. Alternators, just like car batteries, and every other electric component, have a limited lifespan and can simply stop working at any time. The only thing you can do is to replace the alternator when its time has come.

Defective alternator diode

A diode is a semiconductor located inside the alternator and its job is to allow the current to flow in only one direction. In an automobile, the current is allowed to flow only from the alternator to the battery. If the diode burns or simply stops working because of an internal problem, the current will be allowed to travel from the battery to the alternator when the car is turned off, eventually draining the battery completely.

When the car is jump-started, it may run fine for a while but the battery will definitely die every time it’s left unattended for a given period of time.

Overcharging Alternator

An overcharging alternator is a problem that can occur when the voltage regulator goes crazy. When the battery is supplied with more than 15v over a long period of time, it will tend to overheat. Overheating will make the electrolyte slowly evaporate from the battery. Once the level of electrolyte reaches a level too low for the chemical reaction to happen, the battery will simply stop to be able to do its job correctly.

The vehicle may keep running until you turn off the engine. If you jump-start the battery, the engine should be able to run until it is turned off again since the alternator is supplying everything with power but the battery will keep on dying and will need a boost everytime you turn off the engine.

Parasitic current drain

parasitic draw test
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A parasitic current drain is probably the most common cause of a battery repeatedly dying. A current drain happens when an electrical accessory doesn’t shut off when the ignition is turned off. The problematic element stays on and slowly drains the battery while the rest of the car sleeps. When you try to start it the next morning, the battery is totally empty.

If the car is jump-started, it will run great until it’s turned off and the process will start over again. Most of the time, the problem is caused by aftermarket security and audio systems installed in the car but it could also be pretty much any electric or electronic unit.

A parasitic current draw test must be performed in order to locate and fix the problem or the battery will keep on dying everytime the car is left parked for a little while.

Old battery

The last cause of a dying battery is simply its age. As said in the introduction, a battery has a limited lifespan and will need to be replaced on a regular basis. The electrolyte inside the battery is basically sulfuric acid and this causes the battery’s internal components to slowly deteriorate with time. The best advice here is to buy a good quality battery with a decent warranty. Buying cheap isn’t always the cheapest option as replacing the battery more often will end up being more expensive in the long run.


When a car battery keeps on dying, most people’s first reflex is often to replace the battery itself while the problem may really be somewhere else. Always have your car checked by a professional before replacing your dead battery. A quick check-up by a certified and trustworthy mechanic will help prevent misdiagnosis and will save you time and money … and tow truck rides!

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