What is AGM battery

Published On: July 11, 20220 Comments on What is AGM batteryLast Updated: January 31, 20245.7 min read

The lead-fleece battery, also known as an AGM battery (Absorbent Glass Mat), is a sealed, valve-regulated battery. Thanks to the built-in glass fiber fleece, the AGM battery is secured against leakage of the electrolyte (acid) when used in all positions. For the backup and security area and for many other applications, we offer AGM batteries between 2 V and 12 V and 0.8 Ah to 200 Ah – some with VdS approval as VdS batteries – from very powerful manufacturers.

AGM battery

AGM battery / rechargeable battery

Well, first of all, what is agm battery? An AGM battery is a vehicle starter battery designed to do two things: provide powerful starting bursts of electricity and keep the vehicle’s electronics running for a long time. And the decisive advantage: They usually last longer than conventional flooded variants. The acronym stands for “Absorbent Glass Mat” and this is one of the many improvements made to Planté’s original train battery. The glass mats that cushion the ultra-thin lead plates compress like a sponge. In return, manufacturers can squeeze more glass mats and lead into a battery. More lead also means more power. Plus, that squeeze factor means the inside of the battery is tightly packed.

Long Shelf Time

When not in use, the monthly self-discharge rate of this Renogy Deep Cycle AGM sealed battery is as low as 3% at 77℉ (25℃), which is 5 times lower than their flooded counterparts. These also have valves that regulate the amount of hydrogen and oxygen that is allowed to escape during charging. They belong to a broader category of valve-regulated lead-acid (VRLA) batteries, typically used to store a large amount of energy over a long period of time or for continuous operation. AGM batteries were developed in the late 1970s and were used primarily as backup power for telephone booths and early computer rooms. Over the decades, their use has expanded to include motorcycles, the military, airplanes, submarines, and office power banks. Now they are also appearing in everyday cars and trucks. And why? What is the big difference between AGM batteries and traditional flood batteries?

shelf life

How AGM batteries work

The battery’s superpowers stem from two novel additions to Planté’s invention and a series of small design changes that fundamentally expand the possibilities of car batteries. First, a valve prevents evaporated water from exiting the battery case. That might not sound like much more than the reverse of the one-way valves on coffee bean sacks. But this little trick is the secret to the long life of an AGM battery. The basic chemistry is still based on lead, sulfuric acid and water. When you draw electricity, the acid molecules migrate to the lead plates, leaving behind water and lead sulfate. They remove the sulfuric acid from the solution to allow a chemical reaction between the paste on the plates. When charging the battery, this process is reversed. However, there is always a chance that some water loss will occur as electricity splits H2O into hydrogen and oxygen gases. The loss of these water molecules means the electrolyte remains more acidic than usual – reducing the potential strength of the chemical reaction on the plates and ultimately reducing lifespan.

Power Most Appliances

The maximum 1100A discharge (5 seconds) is suitable for appliances that require a high startup current, like a fridge. With a consistent and stable discharge, the battery can power up most common home appliances, such as a microwave, CPAP, coffee maker, laptop, and more. The AGM valve prevents these gases from escaping. Unless you overcharge the battery. If you use the wrong charger for these, the current will have to flow through everything it can. This means more water molecules are broken up and too much gas builds up inside. Then the safety mechanism kicks in, releasing some gas to relieve the pressure built up in the battery. Remember to use deep cycle battery charger.

Second: mats made of fiberglass mesh. They are the GM in AGM (Absorbent Glass Mat) batteries. Ultra-thin glass fibers soak up all the electrolyte (water and sulfuric acid) in thin cushions that cushion the lead plates. Instead of the free-flowing liquid inside a regular car battery, the AGM battery carries its charge in saturated sponges that cover the lead plates. Full coverage by the glass mats makes it easier to get more power out of the starter battery – and makes recharging easier. In terms of performance, speed, longevity and durability, the AGM battery is superior to standard batteries.

powering appliances

What is an AGM battery: The optimal battery for your start-stop vehicle

The lead-acid battery has not changed much in 160 years. Ever since it was invented in 1859, the same 160-year-old technology has been powering your car and almost every car around the world, with minor tweaks here and there. It’s still thin sheet of lead, sulfuric acid, and water (plus a durable polypropylene case). Small improvements and adjustments have been made over the years.

What is the difference between an AGM and a normal car battery?

AGM car batteries have unbeatable advantages over conventional, flooded variants:

  • More starts per battery / per battery
  • Faster charging
  • Higher capacity than conventional batteries (capacity depends on battery wear)
  • More durable construction
  • Safer to handle
  • Leakproof and maintenance free
  • Special valves protect battery life
  • Over its lifetime, battery AGM can start an engine more than 60,000 times. That’s more than three times the launches you can do with a traditional variant.

In addition, they recharge faster than conventional batteries. When the engine is started, this is only slightly discharged before the alternator takes over. The alternator then recharges them – and ensures that all electrical components in the car work. Because of their absorbed mats, AGMs resist shock and vibration better than traditional batteries. They’re also considered leakproof, which means regulations are more lax about transporting them by air or road. That may sound like marketing hype. Instead, it’s pure science.

Where and how are AGM batteries used?

These are commonly found in off-grid power systems, including clean renewable energy systems such as wind and solar power. If you have read a complete guide about how to live off the grid, you will know they are also excellent for powering electric vehicles and uninterruptible power systems, as well as robotics and some ATVs and motorcycles. It is also installed as a start-stop battery in so-called start-stop vehicles. These have an automatic start-stop / start-stop function, which means that the vehicle’s engine is switched off when idling at the traffic light for environmental reasons, so that the environment is protected accordingly. With “standard” batteries, this constant switching on and off over a long period of time can lead to damage and, in the worst case, to complete failure of the vehicle.

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