AGM stands for Absorbed Glass Mat, indicating that the battery acid is absorbed into fiberglass mats instead of remaining as free-flowing liquid.
These fiberglass mats increase the surface area of the electrolyte in contact with the ultra-thin lead plates, while also providing cushioning against impacts, bumps, and vibrations. This design allows battery manufacturers to fit more lead plates into the battery, which translates to greater available power.
Originally developed in the 1970s for applications like telephone boxes and computer rooms (when computers filled entire rooms), AGM batteries feature a sealed design that makes them spill-proof. This quality makes them ideal for use in fighter planes, submarines, motorcycles, and as onboard power sources.
AGM batteries are particularly well-suited for vehicles with auto start-stop engines because they can deliver deep power cycles while still effectively starting the engine.
AGM batteries belong to the category of Valve-Regulated Lead-Acid (VRLA) batteries, which contributes to their durability. VRLA batteries incorporate a one-way valve that controls the release of hydrogen and oxygen gases during the recharging process.
In standard batteries, during recharging, electricity splits water in the electrolyte into hydrogen and oxygen. Most of these gases get reabsorbed, but the remainder escapes through vents, causing water loss. This water loss can reduce the lifespan of traditional car batteries, necessitating periodic refilling with distilled water.
VRLA batteries like AGM batteries, however, do not require the same maintenance. Their one-way valves trap the gases inside, preventing water loss effectively.
Due to their advanced design, AGM batteries often outperform conventional car batteries in numerous aspects.
AGM car batteries offer significant advantages over standard batteries, grounded in scientific principles rather than mere marketing hype.
The key innovation lies in the fiberglass mesh mats—integral to AGM (Absorbed Glass Mat) batteries. These ultra-thin glass fibers absorb the electrolyte (a mix of water and sulfuric acid) into thin cushions that surround the lead plates. Unlike the free-flowing liquid found in regular car batteries, an AGM battery stores its electrical charge in these soaked fiberglass mats, coating the lead plates.
The fiberglass mesh provides a more direct path for electrical current compared to the liquid in a standard battery. This characteristic, known as low internal resistance, enhances the AGM battery's performance capabilities.
In terms of power, speed, longevity, and durability, AGM batteries surpass standard batteries.
Typically, an automotive AGM battery can start your engine more than 60,000 times, which is over three times the number of starts achievable with a standard battery.
For drivers of auto start-stop vehicles, these additional engine starts are crucial. In a typical day, a conventional engine might be started three or four times—commuting to work and running errands. In contrast, an auto start-stop vehicle could require three or four starts during a single morning drive, depending on traffic conditions. Standard car batteries struggle to keep up with the demands of auto start-stop engines, regardless of how well they are maintained.
Moreover, each time the engine shuts off in an auto start-stop vehicle, the AGM battery powers essential systems such as air conditioning, fuel sensors, transmission, and radio, ensuring smooth operation.
Even non-auto start-stop cars strain their batteries due to the numerous onboard electronics like collision sensors and air conditioning. With these demands, the alternator has fewer amps available to recharge the battery, especially at lower speeds. This situation can lead to prolonged periods between recharges for a standard car battery, which is detrimental to its lifespan.
Conversely, AGM batteries can withstand deep discharges and still effectively start engines, making them highly suitable for modern vehicle electronics and demanding driving conditions.
Modern vehicle electronics such as backup cameras and Bluetooth connections can drain deep cycle AGM batteries in ways that standard car batteries cannot handle. Standard lead-acid batteries are traditionally used in cars because they can deliver a high burst of electricity to start an engine, but they require frequent recharging to maintain peak performance, or else they degrade over time.
Deep cycling refers to draining a battery to around 50% capacity before recharging. Regular flooded car batteries struggle with deep cycling, often requiring a jump start if left discharged, such as when headlights are left on without the engine running.
AGM batteries, however, can consistently deliver a steady stream of amps and still provide a robust burst of power to start an engine. They are designed with a tight fiberglass mat structure that allows them to perform well even at partial discharge rates.
This capability makes AGM batteries ideal for applications like boats and RVs, where a reliable power source is essential. For instance, RVs and boats typically use separate batteries—one for starting engines and another for powering electronics. AGM batteries are versatile enough to fulfill both roles effectively. RVs and boats rely on power for devices like fish finders, refrigeration units, cooking equipment, and entertainment systems, often in places without shore power hookups.
Instead of carrying two types of batteries (one for starting and one for deep cycling), owners often opt for a single deep cycle AGM battery that can handle both tasks efficiently.
The absorbed mats give AGM batteries a sponge-like resistance to vibrations. A regular car battery's sensitive internal components can break apart if you shake it hard enough. Its lead plates are hanging from a sturdy metal in liquid. Even if you don't break the plastic case, car batteries can often die from excessive rattling.
An AGM battery's fiberglass mats and special valve provide added protection for its performance in extreme weather conditions.
Heat weakens car batteries by evaporating the water in them. The more fully charged a battery is, the more acidic its liquid becomes, making it harder for the water to evaporate. However, the tightly packed fiberglass mesh in an AGM battery traps this water, and the sealed design retains water vapor. Only in cases of overcharging will water vapor escape.
In cold weather, car batteries struggle to generate the necessary cranking amps, working twice as hard. The tightly packed fiberglass mats in an AGM battery reduce resistance, enabling it to generate ample amps even when chemical reactions slow down due to the cold.
AGM batteries' sealed, spill-proof design meets specific transportation regulations, allowing them to be shipped by air or delivered by mail. Unlike standard car batteries, which can spill or leak like a cup with a sippy cup lid if turned over, AGM batteries are more like sealed soda cans. They can be transported safely without spilling, as long as they are handled gently.
To determine if your car has an AGM battery, you can:
1. Check Online: Look up your vehicle on a battery retailer's website to see the recommended battery type. If an AGM battery is suggested, your car requires an Absorbed Glass Mat battery.
2. Inspect the Battery: Pop the hood and examine the battery label for "AGM." If your battery has raised vent caps, it is not an AGM battery. However, the presence of a valve does not necessarily mean it's an AGM battery.
If you find yourself replacing batteries more frequently than every 3-5 years, consider upgrading to an AGM battery. Consult with an automotive professional before making the switch.
