Does A Weak Battery Affect Car Performance?

Dying battery will cause how my car run?

Like people, a car suffers from a lot of maladies and its battery grows weaker as they grow older. A persistent question that plays in a car owner’s mind is “does a weak battery affect car performance?” Or, is there a direct correlation between the condition of the battery and the car’s efficiency. Let me answer that question and give you some insights on why it does or doesn’t.

Does a failing battery have an effect on the car’s efficiency? Directly, no. A weak battery has no direct bearing on the performance of a car’s engine since its major function is just to crank up and start the engine. But, indirectly, yes. A weak battery affects other parts of the car, such as the alternator and more, that are responsible for making the car perform efficiently.

Proof that a weak battery has no effect on the performance of the car is the fact that once the engine has been cranked you can disconnect the battery and the engine will still continue to run. It will only stop once you switch it off.

The Consequences Of A Failing Battery

A weak battery may not directly affect a car’s efficiency adversely, but it sure has negative repercussions on some car and engine parts that consequently impact on its performance.

1.Shortens the life of the alternator

Once the engine is running the alternator takes over. It runs the car, provides power to most of the electronic accessories, and charges the battery. If the battery is weak, or its voltage level drops below 12 volts, the alternator is made to work harder and this can lead to shortening the life of the alternator.

2. Increases gas consumption

An overworked alternator could also cause the engine to guzzle more gas than is usual. It is directly linked to the accessory belt or drives that the engine turns. When the alternator is working harder than it should, the increased exertion also increases the engine’s gas consumption.

3. Damages the engine’s internal parts

When the level of the battery’s voltage is low, the amps goes up and the temperature also goes up. Overheating could result which could cause damage to the engine.

4. Decreases the performance of car accessories

When the battery is weak the performance of car accessories which are partially powered by the battery suffers. This includes the seats, dashboard lights, power windows, fuel pump, heaters, and the like.

5. Poor delivery of fuel to the cylinders

When your engine sputters while it is in idle mode or the engine running a little rougher or lurching, this could be a sign that the fuel injectors are not delivering enough fuel to the cylinders. This is usually caused by a battery that is not charged properly.

6. Poor performance of the car’s computer

Although a car’s computer may be working adequately, the additional demand of the mechanical and electrical system because of a weak battery may result in a curtailed performance of some of its function.

Some gas sensors such as the oxygen sensor could not be working properly on a voltage lower than what is recommended by the car manufacturer. Because of this, the computer may not be able to correctly determine if the fuel consumption conforms with the rate of the produced exhaust. When this happens, the engine could be using and losing more gas via the exhaust.

The computer may also lose its ability to close some of the engine’s cylinders to conserve gas when driving under a low-intensity condition such as driving at a low speed.

Major Causes Of A Weak Battery

Here are the principal reasons why a battery fails:


Car batteries have an average normal life of three to five years. Some car owners claim that their car batteries last them for as long as ten years, but these are the exception. In general, after the third year, your battery will already be showing some signs of weakness, After every charge, a battery loses some of its ability to hold a charge so that after three years its capacity is no longer as much as when it was new.

2. Acid stratification

Battery stratification occurs when the electrolyte of a battery settles at the bottom, bringing about the lack of acid on the upper half of the cells. Remember that the electrolyte is a mixture of water and sulphuric acid. Since acid is heavier than water, it has a tendency to concentrate at the base of the battery.

Stratification happens when the correct charge (80%) of the battery is not maintained and it is not given the benefit of a full charge. Another contributory factor to this condition would be driving in only short distances while the electric heater and windshield wiper continue to work.

Stratification diminishes the efficiency of a battery and shortens its life.
This condition can be remedied or reversed.

Here’s how:

● Give the battery a top off charge by charging it for at least an hour or two to bring the charge of a 12-volt battery to 18 volts.
● Let the battery rest for several days
● Shake or tip over the battery to remove the acid concentration

When working with batteries be careful not to allow the battery to overheat and lose too much electrolyte from hydrogen gassing. Hydrogen is an odorless gas that could cause an explosion.

3. Sulfation

Sulfation is the accumulation of lead sulfate crystals. These crystals coat the plates and fill the pores of the active material of the lead plates of a battery. It is caused by undercharging, irregular recharging or when the state of charge is brought below 100%.

According to statistics, 85% or a majority of premature failure of batteries is due to sulfation. A battery that is sulfated can result in longer charging hours and reduction of cranking power. It could even cause the battery to stop working or die.

4. Loss of water

Almost half of early battery failures is because of loss of water due to overcharging, overheating, inadequate or poor maintenance, or evaporation because of excessive heat under the hood.

There are other reasons why a battery could fail prematurely, but the four causes above are the real root causes of the problem.

Clues That Indicate A Weak Battery

Before your car battery dies completely, it gives out signals to warn you that it is no longer healthy.

Watch out for these signs:

1.Slow cranking and starting

One sure sign of a weak battery is a slow or sluggish engine crank up. The main function of a battery is to crank up and start a car. Cranking and starting an engine requires enormous power from the battery, if the battery is weak or dying the engine could still crank up but rather slowly.

The engine takes a long time to start. You might even need to step on the gas before it starts, which you normally don’t do.

2. Low or non-existent power for the car accessories

If your battery is totally dead, your car won’t crank up and have accessory power; the headlights, radio, and interior lights won’t turn on. But, if it’s only weak, the lights could still come on, but it will be dimmer than usual.

3. Backfiring

When your engine starts backfiring, better have your car battery check. A weak battery can cause sporadic sparks which can lead to an accumulation of fuel in the cylinders. Once this build-up of fuel is fired up, it fires up abruptly and with great force, and this is the cause of your engine backfiring.

4. “Check Engine”warning

One reason why the Check Engine light in your dashboard is lit could be a weak battery.

5. Low electrolyte level

If the electrolyte level inside the battery is lower than the lead plates, get your battery tested immediately. This is another sign of a failing battery. You can check the electrolyte level from the translucent window in the casing.

6. A swollen or bloated battery case

The bloating or swelling of a battery case which can be due to excessive heat also weakens and shortens the life of a battery.


After reading this article and someone asks you, will a weak battery affect car performance, you can confidently tell him that, no it does not, at least not directly. A battery has very little to do with performance. Its main function is to crank and start the engine. However, a weak battery has a negative impact on some of the car engine parts that are responsible for the car’s efficiency.