How long do stop/start batteries last?

Every starting process is associated with a large amount of energy from a car battery. The battery must be in a very good condition to reliably supply a high starting current. Especially with modern vehicles with automatic start-stop systems, the engine is switched off several times during the journey. During these phases the battery continues to supply all of the electrical consumers with energy. A conventional starter battery (SLI) is not designed for this charge output (i.e. continuous discharging and charging).

Only a battery with start-stop technology can deal with these demands and withstand the strain.

The generator charges the starter battery while driving

In a car which is not equipped with an automatic start-stop system, the starting process is usually a one-off event. While driving, the generator supplies the electrical consumers such as the entertainment system and navigation device, so that if the generator is working, there is no discharge of the starter battery during the journey.

The start-stop battery has a double load

The case is different for cars with start-stop technology. During a journey through the town, the battery is subjected to a series of start and stop periods. If the car is stationary at traffic lights with the engine stopped, electrical consumers such as lights, windshield wipers, radio or displays still need power. The load is increased by continuous discharge and charging.

In particular, short journeys present a challenge for the battery. Especially with old batteries and in winter, the charge acceptance of the battery reduces, so that adequate recharging during short journeys is not always ensured. This can result in gradual discharge of the battery, so that at some point, the battery no longer has enough energy to start the engine. Due to the special technology, the internal resistance of AGM batteries remains considerably lower than that of conventional batteries over their entire life, so that sufficient charge acceptance is also ensured over a long period and short journeys with many start-stop phases can be handled better by AGM batteries.

Three advantages of AGM batteries

Excellent cold-start characteristics

AGM batteries have a large cold start current. They powerfully start the starter motor and reduce its running time. Thanks to the cycle stability of AGM batteries the engine can be switched off and started again several times at short intervals, without the risk of difficulties when restarting.

Balanced state of charge

With modern vehicles, the AGM battery is not only charged by the generator, but is also fed by the braking energy recovery system. Normal starter batteries must be kept permanently fully charged and can therefore not absorb the energy which is generated by recuperation. AGM batteries can be operated in the partial charge range and therefore provide sufficient “extra” capacity to store the energy which is generated on braking.

High reserve capacity

The high reserve capacity ensures the power supply for all types of electrical components. The cycle stability of AGM technology ensures the power supply to components while also providing a high starting power. Even if the battery is not fully charged, because, for example, electronic assistants and consumers which ensure comfort are supplied during a stop, or the generator has been temporarily decoupled to reduce the load on the engine.

Interesting facts about start-stop technology

Start-stop systems require a battery with modern technology, because normal starter batteries are not designed to meet the higher demands of these vehicles.

The architecture of the electrical system in modern vehicles requires a compatible battery technology in order to function properly and reliably. For this reason, in many vehicles, new batteries must be “registered” – the Battery Management System (BMS) must know what type of battery is installed in the vehicle in order to exploit its full potential. If an incorrect battery is installed in the vehicle or is not correctly registered, this can result in premature battery deterioration and another breakdown.

For this reason, only EFB or AGM batteries should be installed in vehicles with automatic stop-start systems. If an AGM battery is already installed in the vehicle, it must always be replaced with another AGM battery.

There is no simple answer, but based on decades of industry experience, we know that three key factors affect the life of a car battery: time, heat and vibration.

Car batteries have a finite lifespan

Batteries gradually deteriorate until they can no longer provide enough power to start an engine. This wear time could take three to five years and a vehicle's usage pattern is one factor contributing to the rate at which a battery will age. Batteries in cars driven mostly on short trips may not fully recharge and batteries in vehicles parked for extended periods naturally self-discharge. In either case, using a maintenance charger like AAA's Battery Tender will keep the car battery fully charged and extend its service life.

Where you live affects your car battery

Heat facilitates the chemical reaction car batteries use to generate electricity, but it also increases the rate of battery degradation. In cooler northern climates, a battery may last five years or longer, but in hot southern locales, a car battery will typically last approximately three years.

Batteries reside in a harsh under-the-hood environment where temperatures can easily exceed 200 degrees Fahrenheit in hot weather. To combat this heat, automakers may mount the battery in an isolated area, install a heat shield over the battery, or relocate the battery outside the engine compartment, often under the back seat or trunk floor.

Hold down hardware prevents excessive vibration

Vibration causes internal battery parts to break down. To minimize vibration effects, use special hold down hardware to secure the battery in place and prevent it from moving. Missing or loose hold down hardware can significantly shorten battery life.

Malfunctioning charging system reduces car battery life

While less common than the aforementioned factors, a malfunctioning charging system will also reduce battery life. Persistent under- or over-charging accelerates battery aging. Some newer cars with absorbent glass mat (AGM) batteries require careful control of charging rates for maximum battery life, and the automaker may even alter the charging strategy as the battery ages. Finally, allowing any car battery to go completely dead will take a big chunk out of its lifespan, even if you can recharge and put the dead battery back in service.

Weak battery warning signs

You may have a battery problem if the starter motor cranks the engine slowly or the Battery/Charging warning lamp illuminates on the dashboard. In older models, dim incandescent headlights, particularly when the car is idling, indicates a weak battery.

Not every failing battery reveals itself through obvious symptoms so take precautions to avoid a dead battery situation. Inspect the car battery at every oil change. Make sure the cable connections are clean and tight and the hold down hardware is secure. Once a battery reaches its third year, have it tested annually. A car battery test identifies the deterioration level so you know when it is time to install a replacement battery. More information available in the Things to know about your car battery article. AAA members in most areas can request AAA car battery service. A professional service tech will come to your location, conduct a free diagnostic test of your car's battery and starting and charging systems, and if needed, install a new battery on the spot.

Car batteries are not one-size-fits-all

You must consider the battery type, physical size, terminal configuration, and cold cranking amps (CCA) or amp-hour (Ah) rating to ensure you get a car battery that properly fits and functions for your make and model vehicle. Installing an incorrect battery can adversely affect the car's electrical system and cause major damage if the terminal locations create a short circuit with nearby components. If you are not sure which car battery to buy, ask your auto repair professional or consult your owner's manual.

Install the correct replacement battery

Batteries are either conventional lead-acid or the more advanced AGM design previously mentioned. Most cars on the road today use conventional batteries and some models use AGM batteries. These batteries are highly spill resistant and better able to handle repeated discharging and recharging, as occurs in cars that have engine stop-start systems to improve fuel economy. Auto manufacturers optimize car-charging systems for the battery type so AAA recommends that your replacement battery always be the same type as the original factory-installed battery.

What is a car battery group number?

The group number, for example Group 24, is an industry standard that defines the battery's physical size, its hold down configuration, and the type of terminals and their location. Selecting a battery with the same group number as the original equipment battery will ensure a secure fit, adequate clearance, and no cable/terminal issues. It will also allow for proper reinstallation of the important battery heat shield, if your vehicle has one. Some imported vehicles use batteries that conform to European or Asian battery standards. In many cases, a standard group number battery will fit with minor or no modifications, but pay special attention to ensure that the installation does not pose any problems. Refer to the application guide available where you purchase the battery. If you prefer, trust a AAA car battery service tech to install the correct part.

In a limited number of cars, the vehicle design makes a factory replacement battery the only possible option.

What is a cold cranking amps rating?

The cold cranking amps rating, for example 650 CCA, is an industry standard measure of how much electrical power a battery can provide at zero degrees Fahrenheit. Never confuse this rating with "cranking amps" (CA), a rating based on an easier test that produces inflated numbers. Some import automakers state battery power requirements using an amp-hour rating, for example 78 Ah. This rating is based on the number of minutes a battery can provide a specified level of electrical current, typically 20 amperes. To avoid electrical system problems and a visit to the repair shop, never install a battery with a CCA or Ah rating that is lower than what the vehicle manufacturer recommends. A higher-rated battery will work if it fits properly, but is usually unnecessary and may have a shorter service life in hot climates.

Purchase replacement battery from high-volume seller

When your car needs a new battery, always purchase one from a high-volume seller with fresh stock. You do not want a battery that has already lost a good portion of its service life sitting on a shelf. Also, look for a battery with an extended full-replacement warranty. Quality batteries offer free replacement for three or more years if there is a problem within that period. A warranty that enters a pro-rated replacement period sooner will require a partial payment to replace the battery once the full-coverage term expires.

Choose quality auto repair service

Use AAA's auto repair shop locator to find information on Approved Auto Repair centers near you that meet AAA's high standards for technician training and certification, insurance coverage, customer satisfaction and more. AAA regularly inspects every

Approved Auto Repair facility and surveys customers to ensure ongoing quality performance.

As a AAA member, you receive special benefits that include auto repair discounts, an extended 24-month/24,000-mile parts and labor warranty, and AAA assistance in resolving repair-related issues.