Battery Maintenance FAQs

How does a battery work?

Your battery does what it does best when it’s sitting idly under your hood. It stores chemical energy when it has nothing else to do, and waits to release it as electricity when you need it. When you put your key into the ignition and turn it to the “ON” position, your battery receives a signal to go into action. It releases that stored chemical energy as electricity. This is what allows the engine to crank.

Why won’t my car start?

One of the reasons is a weak or dead battery. If you have a battery tester that can measure cranking amps, use it to see if the battery is weak. If you can’t test the battery, try jump-starting . If the car starts right away, your problem is most likely a dead battery. Charge the battery and clean the terminals and cable connectors to ensure good contact. If your car does not start by jump-starting, you may have a problem with your starter, alternator or another component of the electrical system. Be sure to read and follow all safety and handling instructions on the battery and this website.

How do I charge a lead-acid battery?

To charge an automotive battery, refer to your owner’s manual and your battery charger manual for instructions. Read and follow all safety and handling instructions that came with your charger and battery. Battery chargers will charge a battery based on its condition and at a rate appropriate for its state of charge. Charging voltages run from 13.8 volts to a maximum of 15.5 volts for most applications. Finally, remember that batteries contain sulfuric acid that can cause severe burns, and hydrogen-oxygen gases that can be explosive. Charge in a well-ventilated area. Be sure to follow all safety and handling.

How do I jump-start my vehicle?

See the step-by-step instructions on our Jump-starting page. You’ll need a set of jumper cables and another vehicle with a charged battery. You can find cables at gas stations, auto parts stores or just about anywhere you buy car parts. Be sure to read and follow the safety and handling information on the battery, this website, and on the jumper cables.

Do I need to charge my battery after I jump-start my vehicle?

We recommend fully charging your battery at the first opportunity after its being jump-started.

When fully charged, what should the voltage of my battery be?

A 12-volt battery is considered fully charged at 12.6 volts.

Will letting my vehicle idle charge my battery?

Idling or frequently making short stop-and-go trips will not recharge the battery effectively.

Should I remove the vent caps before charging my battery?

Charging should never occur without vent caps. In general, vent caps should always remain tightly in place and in a level position.

What should I consider when buying a battery?

There are several key factors you should consider. If you are unsure of the requirements in any of these areas, check your vehicle owner’s manual or ask your mechanic about the original equipment manufacturer’s recommendations for:

Technology Type
Battery group size
Cold cranking amps (CCA)
Reserve capacity (RC)

Find the right battery for your vehicle with our Battery Selector. Consult a replacement guide to ensure that the replacement battery fit properly (with the correct clearance) under the hood or trunk lid.

What is the difference between deep-cycle and starting batteries?

Starting, Lighting, Ignition (SLI) – These batteries deliver a large burst of power for a short time as needed for normal engine starting. The battery is then recharged by the alternator. Unlike a deep-cycle battery, starting batteries are not designed to withstand multiple discharge/recharge cycles, and draining it can significantly shorten its life.

Deep-Cycle – These batteries are designed to provide a steady amount of current over a long period of time. Deep-cycle batteries can be repeatedly discharged and recharged without causing damage or shortening their life. They are well-suited to power numerous electronics and plug-in accessories, or other applications that place high demands on them.

Some deep-cycle batteries can be used for engine starting as well (these are sometimes referred to as dual-purpose), but be sure to check the CCA rating to ensure the battery has sufficient starting power.

What kind of preventive maintenance can I do for my battery?

Check your battery every now and then to make sure the battery terminal connections are clean, snug and protected from the elements. Signs of corrosion or leaks could mean that the battery is no longer operating optimally.

Secure the hold-down bar. This ensures that your battery is snugly seated and will help minimize vibration which can be detrimental to certain types of batteries.

Routinely test your battery to make sure it is correctly charged. This allows you to recharge your battery, if needed, to maintain its peak performance. It’s important for your battery’s health to get it tested at least once a year to keep it at its optimal performance level.

Be sure to read and follow all safety and handling instructions on the battery and this website.

How should I store my batteries?

If storing your vehicle or battery for an extended period of time, aim to keep the battery charged at full capacity throughout the storage period. You can do this by using a battery maintainer – a device that will monitor your battery and keep it at full capacity during storage. If it is not possible to use a maintenance charger, you should fully charge the battery prior to storage and then disconnect it from the vehicle to prevent small electrical drains (such as in-car clocks, security systems and so on) from draining it. Check the battery voltage periodically and recharge it if it falls below 12.6 volts.

What are the main causes of battery failure?

Common Causes:

High temperatures: Heat is the No. 1 cause of battery failure. Heat accelerates grid corrosion and grid growth in the positive plate. As heat corrodes the positive grid, the battery loses capacity and starting power, which weakens its ability to start an engine – particularly in colder weather.
High vibration: Vibration can damage and separate internal components, which ultimately lead to reduced starting performance or even battery failure.
Deep drains/failure to recharge after drops in voltage: When a battery is discharged, the active materials produce lead sulfate crystals inside the plate that are called discharged material. If these crystals are not recharged, they eventually combine to form larger crystals. These bigger crystals are harder to dissolve and recharge, and eventually they lead to battery failure by disrupting the plate structure.
A faulty alternator: A faulty alternator will lead to an undercharged or completely discharged battery. An undercharged battery has reduced capacity and starting power. If the battery is continuously undercharged because of a weak alternator, the battery will become deeply discharged and sulfation will occur.

Other Possible Causes of Failure:

Battery application and installation
The battery is not being used in the application for which it was designed. A common mistake, for example, is using an SLI (starting-lighting-ignition) battery in a vehicle that requires a deep-cycle battery.
The battery is not sized properly for the application.
The vehicle has too many electrical accessories.
The battery is not properly installed.

Service and maintenance
The battery cables have not been cleaned and properly adjusted to fit the battery terminals.
The vehicle’s electrical system has been repaired or altered.
The vehicle has been in long-term storage.

I only drive my car a short distance to work every day and have no accessories, yet it keeps going through batteries. What’s the problem?

If your driving style is mostly short trips several times a day, you might not be giving your alternator enough time to recharge the battery after starting the car, which causes a quick voltage drop. There are several factors that affect an alternator’s ability to adequately charge a battery, including:

How much current (amperage) from the alternator is diverted to the battery to charge
How long the current is available (drive time)
Battery temperature (in cold climates batteries take more time to charge)
Battery age

If the vehicle is not driven far enough to let the alternator fully recharge the battery, use a battery charger to restore it to full capacity.

Should I add water to my battery?

Under normal conditions the battery should not require adding water during its life. Certain circumstances, however, such as a charging system failure or extreme high temperatures for an extended length of time, can cause the electrolyte level to drop. Should these occur, take the battery to a mechanic or an auto service professional to determine if it needs water.

Note: There is no free electrolyte in a VRLA (Valve Regulated Lead-Acid) battery. No effort should be made to test or adjust its electrolyte level.

What is sulfation and how do I prevent it?

The term sulfation describes the accumulation and growth of lead sulfate crystals inside the plates when a battery is in a discharged state for an extended period of time. Sulfation begins as soon as voltage level gets too low which, in the case of a 12-volt battery, is below 12.6 volts. If the crystals are not recharged, they eventually combine to form larger crystals. These bigger crystals are harder to dissolve and recharge, and eventually they lead to battery failure by disrupting the plate structure. Sulfation decreases battery performance by blocking the chemical reaction that allows the battery to hold its charge.

Sulfation can be reversed by using a charger that has a de-sulfating mode, which will slowly dissolve the lead sulfate crystals and recharge them back to active material.

How do you perform a load test?

To pass a load test, the battery must maintain 9.6 volts at 15 seconds when tested at one-half the CCA rating and 70°F (or above). This test must be done with a true load (carbon pile) and not one of the hand-held testers that work off a conductance algorithm. The test must be run with the battery in a high state of charge. Be sure to read and follow all safety and handling instructions on the battery, this website and your battery tester.

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