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What Is an AGM Battery?

A Kia Telluride factory AGM battery.

The absorbed glass mat battery (AGM) is a recent battery technology that is increasingly common in today’s cars. It’s an alternative to the well-known wet cell, or flooded, battery that has been in use for years. Read on to learn the difference between these battery types and why you might want to consider an AGM battery for your car.

What Is a Flooded Battery?

A flooded battery is the traditional type found in most vehicles. Inside these batteries there are thin lead plates and a solution of sulfuric acid and water. Car owners used to have to top off this water regularly, but many of today’s flooded batteries are sealed and don’t need this type of maintenance.

What Is an AGM Battery?

An AGM battery still has the lead plates and the solution of sulfuric acid and water. The difference is an added spongy glass mat separating each plate. The glass mats press up against the plates, holding them firmly in place and allowing for more of them to be packed into one case.

Since the liquid solution is held in the sponges, there’s never a need to fill these batteries. This design also reduces the risk of spillage in the event that the case is broken or tipped on its side.

Which Battery Is Best?

NAPA The Legend Premium AGM Battery

The AGM battery is a newer technology, but that doesn’t make it better in every situation. Each type of battery has pros and cons to consider.

A flooded battery has the advantage of being able to discharge to 80% without causing any harm to the battery. An AGM battery can only be discharged to 50% without risking a shortened lifespan. Overcharging an AGM battery can also shorten its lifespan.

An AGM battery is safer to handle since it won’t leak caustic fluids like a flooded battery, and it can have a longer lifespan. On the cons side, AGM batteries can be more expensive than traditional flooded batteries, which may put an AGM battery out of reach for people on a budget.

While both batteries can power your car sufficiently, be sure to find a battery that’s rated for your vehicle and fits securely in the engine compartment. Not every battery fits in every car, so do your research before you decide whether an AGM battery is the right choice for you.

Check out all the batteries and battery accessories available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information about automotive batteries, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Nicole Wakelin View All

Nicole Wakelin covers the automotive industry as a freelance journalist for a variety of outlets. Her work includes news pieces, podcasts, radio, written reviews, and video reviews. She can be found in The Boston Globe, CarGurus, BestRide, US News and World Report, and AAA along with lifestyle blogs like Be Car Chic, The Other PTA, and She Buys Cars. She is active on social media with a large following on both Twitter and Instagram and currently serves as Vice President of the New England Motor Press Association.

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