Battery Failure: Six Reasons Why Your Car Won’t Start

Image of jumper cables attached to a battery

Several times a month, we get calls regarding vehicles that will not start. The symptoms range from a clicking noise when cranking to an engine that makes no sounds at all. The driver usually explains that the problem seems to have come from out of nowhere, or that their car won’t crank after several days of inactivity. There are several possible root causes of this problem, all of which relate to the vehicle’s battery.

Abnormal voltage levels

Infrequent use or overcharging causes abnormal voltage levels, which can make it much harder for a car battery to function properly. When a technician receives a repair request for a vehicle that won’t start, usually the first task is to test the battery’s state of charge. Normal battery voltage should be around 12.6 volts. Any voltage reading under 12.5 volts will raise an eyebrow, and a voltage reading significantly higher than 12.6 volts may indicate the charging system is overcharging the battery.

A recently-driven vehicle’s battery voltage might be a little higher due to what’s called a surface charge, which can cause a reading that is a couple tenths of a volt above normal. However, if the voltage is noticeably above that, it indicates a potential problem with the charging system.

A battery can also experience a certain degree of “self-discharge,” which means that it isn’t recharged frequently enough and will eventually lose some of its stored energy. Battery age can reduce the “standby” length prior to a failure to start. If the vehicle hasn’t been driven for four or five days, you can expect the voltage readings to be low. Voltage loss will be determined by the number of components the battery is supplying power to, its age and internal condition, ambient temperature, and how long the vehicle has been sitting. However, a charger at the correct setting can usually bring the battery back to life. 

Deep discharging and over-consumption 

Deep discharging, which happens when the state of charge is below 10.5 volts for an extended period of time, usually causes sulfating, or the accumulation and growth of lead sulfate crystals on the battery plates.  In simplistic terms, if a battery stays in a discharged state for too long any crystals that have formed under normal operating conditions will eventually combine to form larger crystals, which makes recharging even more difficult. Severe crystal formation eventually leads to a reduction of negative and positive plate capacity, which will one day lead to battery failure.

In addition, when your engine is off, the battery must provide all the necessary energy to power auxiliary functions such as interior lights, audio equipment, windows, door locks, etc. Leaving these components running for too long can deplete the battery’s state of charge and send you scrambling for your roadside assistance card.

Corrosion On Battery Terminals

Intense environmental conditions

Climate significantly affects battery life. In the Southeast, battery life averages three to four years, but in some areas of the country—including parts of the Midwest and Northeast—a battery may last for over five years.

In other words, increased exposure to excessive heat or cold (especially heat) reduces the life expectancy of a battery by increasing the intensity of what’s referred to as thermal cycling. The plates in the battery expand slightly when exposed to heat and contract slightly when exposed to colder temperatures. Over hundreds of cycles, this can warp the battery plates.

Extremely hot climates reduces battery life even further, to an average life expectancy of (approx.) 30 months. It’s especially important to keep track of your battery’s age in such climates. Battery failure is often unpredictable under these conditions.

Improper battery placement

If a battery is not secured properly in its housing (for example, due to a loose or missing hold-down clamp), the excessive movement and vibration that it is subjected to can cause the material on the battery plates to flake off, compromising the battery’s ability to function properly.

Water loss

Battery failure is frequently caused by loss of the water required to maintain normal discharging and recharging functions. In fact, water loss due to high ambient temperatures, hotter under-hood conditions, poor maintenance, and overcharging causes a good number of battery failures each year.

Poor connections

Corrosion and oxidation of battery posts and terminals can be a big problem. The gasses that escape the battery case when recharging is a major contributor to corrosion and acid formation. Dissimilar metals (battery posts, terminals and copper wiring) can also accelerate corrosion and acid build up. Corrosion is a poor conductor of electricity, because it increases circuit resistance, which in turn can have an effect on starting and charging.

This list isn’t exhaustive, of course. There are many other causes of battery failure, and some batteries are simply faulty, failing well before the end of their warranty despite proper care. However, the vast majority of the time, you can get the maximum value out of your battery’s life by taking some common-sense precautions to protect it from environmental, electrical, and physical damage. If you’re concerned about the condition of your battery, contact us to schedule an inspection.

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