EnerSys® Experts Answer Auxiliary Battery Frequently Asked Questions

For today’s technologically advanced vehicles and their lavish onboard accessories, there’s a new approach to starting up the engine while helping to ensure all in-cabin applications stay in operation. In addition to the main battery source, an auxiliary
battery – such as the ODYSSEY® Extreme ODS-AGM14 battery from EnerSys – provides long-lasting back-up power for anything from lighting and navigation to the latest state-of-the-art stereo systems without running the vehicle’s motor.

As with any new product that comes to the market, it’s only natural that costumers will have questions about what an auxiliary battery is and what makes it different from other battery chemistries such as Lithium-ion and traditional flooded lead acid batteries.

To ease the confusion, our team of ODYSSEY® battery experts at EnerSys® weigh in on our customer’s frequently asked questions. As always, be sure to follow the manufacturer’s guidelines for battery care and handling and direct all questions to a battery professional.

What is an auxiliary battery?

Auxiliary batteries are typically small 12-volt batteries that are used in your car or light truck to offer additional power when the engine is not running. This is usually the case on cars equipped with a start-stop feature, which is when the engine shuts off when the vehicle is sitting idle.

How do I know if my auxiliary battery is bad?

Most cars that are sophisticated enough to have an auxiliary battery also have a computer system in the car that can alert you when there are issues with the battery or it’s starting to fail. An error on the dashboard is usually the first indication that something isn’t right.

Can an auxiliary battery stop my car from starting?

While the main battery is the one that will be primarily in charge of starting the engine for your car, an auxiliary battery can help run other systems in the car that can be adversely affected if it is not functioning properly. In some cases, it can assist if your main power source fails, but may not actually provide any “starting” duties itself.

Do all cars have an auxiliary battery?

No, not all cars have auxiliary batteries. It all depends on the vehicle size and model as well as the location, design and number of onboard accessories. Always replace your auxiliary battery with the proper size and type battery for your application. Just because a battery may look similar to another battery, it is not wise to assume that they are interchangeable. When in doubt, defer to your vehicle manufacturer for more information.

How do you charge an auxiliary battery?

Typically, charging will be done within the vehicles normal charging system. If a vehicle is left to sit idle for a long time, especially in extreme temperatures, it might be necessary at some point not only to charge the main battery, but also the auxiliary battery. Since both sources of power are 12-volt batteries, they would be charged in a similar manner. Please refer to the original manufacturer for proper battery charging guidelines.

What makes an ODYSSEY® battery from EnerSys better suited for an auxiliary application than other products on the market?

ODYSSEY® batteries are made from pure lead. This construction allows the battery a unique ability to deep-cycle (deeply discharge, and recharge). The proprietary Thin Plate Pure Lead (TPPL) technology found within ODYSSEY® batteries enables them to recover faster and are not damaged by extended discharges. This is something that cannot be said for the competition, even the original battery that came with the vehicle.

In particular, the ODYSSEY® Extreme ODS-AGM14 model has the proper vent designed into the battery that is compatible with the factory venting system which is needed in some models when the battery is mounted inside the vehicle. It is an excellent option if you’re looking to take your technologically advanced vehicle to the next level of luxury and performance.

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EnerSys, the global leader in stored energy solutions for industrial applications, designs, manufactures and distributes energy systems solutions and motive power batteries, specialty batteries, battery chargers, power equipment, battery accessories and outdoor equipment enclosure solutions to customers worldwide. The company goes to market through four lines of business: Energy Systems, Motive Power, Specialty and New Ventures. Energy Systems, which combine power conversion, power distribution, energy storage, and enclosures, are used in the telecommunication, broadband and utility industries, uninterruptible power supplies, and numerous applications requiring stored energy solutions. Motive power batteries and chargers are utilized in electric forklift trucks and other industrial electric powered vehicles. Specialty batteries are used in aerospace and defense applications, large over-the-road trucks, premium automotive, medical and security systems applications. New Ventures provides energy storage and management systems for various applications including demand charge reduction, utility back-up power, and dynamic fast charging for electric vehicles. EnerSys also provides aftermarket and customer support services to its customers in over 100 countries through its sales and manufacturing locations around the world. More information regarding EnerSys can be found at


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