The lead-acid battery hasn’t needed to change in 163 years. Then the driving experience evolved. The lead-acid battery hasn’t changed much in 163 years. Developed in the late 1970s, AGM battery mostly served as backup power for telephone boxes and early computer rooms.
Since it was invented in 1859, the same 160-year-old technology still starts your car and nearly every car around the world, with minor changes here and there. It’s still thin lead plates, sulfuric acid and water (plus a durable, polypropylene case.) Small tweaks and adjustments played out over the years. Some are even sealed so you don’t need to add water.
Despite these tiny developments in across a century and a half, French physicist Gaston Planté could step out of a time machine and still recognize his invention in 92.4% of the US automotive market. He might be surprised how little the lead-acid battery changed in 160 years.
Because everything else has.
What sparked the next generation of car batteries?
Driving in 2019 just isn’t the same experience it was in 1969.
Touchscreens. Artificial intelligence-assisted driving. Seat warmers. Vehicles capable of fuel economy fuel economy in the high 20s to mid-30s. Autonomous driving. Auto-tensioning seat belts. Start-stop engines. Remote starting, even phone-operated starting. Backup cameras with calculated guidance routes. Satellite-connected radio and wireless-fidelity internet connections. Bluetooth-enabled sound systems to play music from your smartphone (which you barely use for calls anymore. Poor Alexander Graham Bell.)
Here’s the problem: Planté’s lead-acid battery can’t handle all those power needs for long.
Lead-in-acid batteries used to fit the bill for cars because they can throw a lot of electricity into a starter in a short burst. They’re also inexpensive to make. However, a standard, flooded battery can’t run a light bulb for more than a couple hours in one stretch. Much less your air conditioning.
The next generation of batteries can. Enter the absorbed glass-mat (AGM) battery.
What is an AGM Battery?
What does “AGM battery” mean? Although they have been around since the 1970s, most people don’t know what AGM stands for. The term AGM battery is short for Absorbed Glass Mat. AGM batteries have become increasingly popular in recent years. The wide use of AGM batteries is largely due to their unique design. The way in which they’re constructed provides AGM batteries with a higher voltage output, which allows them to support the increasing amount of technology found in modern and heavy-duty vehicles.
Are you looking for the best battery for your car, truck, RV, golf cart, boat or powersport vehicle? An AGM battery may be the answer. Today, we’ll be discussing how AGM batteries work, looking at the various features of AGM technology and what advantages AGM batteries have over traditional lead acid batteries. We’ll also be talking about deep cycle AGM batteries and what to look for in an AGM battery charger.
An AGM battery is a car battery designed for two jobs: delivering powerful bursts of starting amps and running electronics for a long time.
And here’s the big deal: They tend to last longer than a regular flooded battery.
The acronym stands for “absorbed glass mat” and that’s one of many improvements made to Planté’s original train light battery. Glass mats, cushioning the ultra-thin lead plates, will squish like a sponge. In turn, manufacturers can squeeze more glass mats and lead into one battery. More lead equals more power. Plus, that squish factor means the battery’s insides are packed tightly.
AGM batteries also have valves regulating the amount of hydrogen and oxygen gas allowed to escape during charging. They fall under a broader category of valve-regulated, lead-acid (VRLA) batteries, typically used for storing a lot of power for a long time or for long-running power uses.
Developed in the late 1970s, AGM batteries mostly served as backup power for telephone boxes and early computer rooms. Their use expanded over the decades to include motorcycles, military, aircraft, submarines and power banks for offices.
Now, they’re showing up in everyday cars and trucks. Why? What’s the big difference between AGMs and a standard, flooded battery?
What’s the Difference Between an AGM and a Regular Car Battery?
AGM car batteries have unbeatable advantages over standard, flooded batteries:
- More starts per battery
- Faster recharging
- More durable construction
- Safer to handle
- Special valves protecting the battery’s lifespan
Over the course of their lifespan, AGM batteries can start an engine more than 60,000 times. That’s more than three times the starts you’ll get out of a conventional battery.
And AGMs recharge faster than typical batteries. Starting your engine depletes your battery only a small amount before the alternator takes over. When it does, the alternator recharges the battery — and keeps all the electrical components running in the car.
Because of their absorbed mats, AGMs withstand shaking and vibration better than typical batteries. They’re also listed as spill-proof, meaning the regulations are more relaxed about transporting them by air or by road.
This might sound like marketing hype. Instead, it’s just science.
Here’s how AGMs work.
How Do I Know if My Battery is AGM?
AGM batteries are constructed a bit differently than flooded batteries. They still contain plates and an electrolyte, however, in an AGM battery, the plate separators are made of a special fiberglass material.
What is AGM Battery Technology?
In a traditional flooded battery, the electrolyte is a free-flowing liquid, but an AGM battery absorbs the electrolyte in its separators and holds it there in suspension. It is the fiberglass material that helps enable AGM batteries to store the electrolyte in a dry state rather than in a liquid free form. This is what the term “absorbent glass” is referring to.
How AGM Batteries Work
The superpowers of an AGM battery come from two novel additions to Planté’s invention and a host of small design changes that fundamentally expand what car batteries can do.
First, a valve prevents evaporated water from leaving the battery case. This might not sound like much more than the inverse of the one-way valves on coffee bean bags.
But this little trick is the secret to an AGM’s long life. Here’s how.
Its fundamental chemistry is still based on lead, sulfuric acid and water. When you draw power, the acid molecules move to the lead plates, leaving water and lead sulfate. You are removing the sulfuric acid from the solution to enable a chemical reaction between the paste on the plates. This process is reversed when you charge the battery.
However, there’s always a chance some water loss can happen when electricity splits H2O into hydrogen and oxygen gases. Losing those water molecules means the electrolyte stays more acidic than usual — cutting into the potential strength of the chemical reaction on the plates, and ultimately shortening the life span.
The AGM’s valve stops those gases from leaving.
Except if you’re overcharging the battery. When you use the wrong charger for an AGM, the current must pass through anything it can. That means breaking up more water molecules and building up too much gas inside. That’s when the safety mechanism kicks in, releasing some gas to reduce the pressure built up inside the battery.
Second: fiberglass mesh mats. They are the GM in AGM (absorbed glass-mat) batteries.
Ultra-thin glass fibers soak up all the electrolyte (water and sulfuric acid) into thin pillows cushioning the lead plates. Instead of the free-flowing liquid inside of a regular car battery, the AGM carries its charge in soaked sponges coating the lead plates. The glass mats’ complete coverage makes it easier to summon more power from an AGM battery — and make it easier to recharge.
In power, speed, long life and durability, the AGM battery has standard batteries beat.
So, why are AGMs in fewer than 9% of the cars on American roads?
Are AGM Batteries the Same as Valve Regulated Lead Acid Batteries?
You might have heard AGM batteries referred to as Valve Regulated Lead Acid batteries or VRLA for short. AGM batteries are one kind of VRLA battery. The key thing about VRLA batteries is that they’re constructed with a special valve that prevents gases from escaping the battery’s casing.
So, why is that important? Lead acid batteries work by converting stored chemical energy into electrical energy. This is done through a series of chemical reactions that take place between the battery’s plates and the electrolyte. During this process, the water in the electrolyte is split into hydrogen and oxygen gases. When that happens, it’s possible for a flooded battery to lose some of its water due to evaporation. That’s why flooded batteries require you to occasionally add distilled water to them in order to prevent them from becoming too acidic over time, which will shorten the battery’s overall lifespan.
Because a VRLA battery is completely sealed, it prevents any gas from escaping, allowing it to recombine into water during the recharging process. This preserves the electrolyte’s proper chemical concentration, giving the battery a longer life.
What are the Advantages of an AGM Battery?
Due to their unique design, AGM batteries have a lower internal resistance than flooded batteries. This provides them with a number of advantages.
- Higher voltage output – AGM batteries provide more electrical energy than flooded batteries, making it easier to start vehicle engines and providing additional power for technology such as touchscreens, backup cameras and fuel-saving start-stop systems
- Faster recharge rates – AGM batteries recharge up to five times faster than a flooded battery.
- Longer lifespans – How long do AGM batteries last? AGM batteries can last up to two to three times longer than flooded batteries. Their long lifespans can be cost-effective in the long run for consumers.
- Slower discharge rates – An AGM battery holds its charge longer when it’s not being used and is more likely to be recovered if it becomes completely drained.
- Spill-proof – Because the electrolyte is held in place by the plate separators, AGM batteries are spill-proof. This allows you to mount an AGM battery in a variety of positions that aren’t possible with a flooded option.
- Weather resistance – AGM batteries do a much better job of standing up to the negative impact of extreme cold and heat.
- Vibration resistance – AGM batteries are more resistant to vibration, making them ideal for boats and personal watercraft.
Driving evolved. So have our expectations.
Today, 91% of the cars on the road don’t need an AGM battery.
However, AGM batteries won’t stay in the fringes for long. Proud owners of these advanced batteries are on American highways.
They just don’t know it until they drive into a shop.
Hybrid electric vehicles and start-stop vehicles need an advanced battery to keep the air conditioning running, even if the engine turns off. So do vehicles with futuristic-level technology: lane-keeping assistance, pre-collision warnings, remote engine starting and keyless entry and ignition.
In 2014, you could count the number of vehicle models that needed an AGM battery on your two hands.
Today, at least 15 million vehicles from their manufacturer are equipped with an AGM battery. Plenty of 2015 and 2016 models still use a standard battery, but more and more vehicle models are employing always-on tech. That means battery power. And that’s an AGM.
However, consumer expectations rarely stand still. The more that we expect from our phones, the more we expect from our cars.
Safety, reliability, comfort always mattered to drivers. Technology and new inventions merely expand how engineers and car companies express these values.
How might tomorrow’s tech look in these cars? Auto-buckling seatbelts. DNA-coded locks. Touchscreen windows. Engine parts using super-materials to avoid breaking or ever needing to be replaced. Maybe a flying-mode, too.
The possibilities are endless. As long as you have the right battery.
Can AGM Batteries Be Used for Deep Cycle Applications?
One of the unique things about AGM batteries is their ability to function as both SLI (Starting, Lighting & Ignition) and deep cycle batteries. SLI batteries are the type of battery that’s used to start the engine in your car, truck or RV. They’re built to provide short intense bursts of energy. Deep cycle batteries are engineered to provide smaller, more reliable amounts of power over a longer period of time. You can commonly find deep cycle batteries in applications like golf carts and floor scrubbers. They’re also commonly used as the house battery in RVs and boats.
Are AGM Batteries Good for RVs and Boats?
It’s common for owners of RVs and boats to have two different types of batteries on board, a starting/cranking (SLI) battery to start the engine and a deep cycle battery to power additional applications such as clocks, lights and appliances. Due to their higher voltage output, AGM batteries can serve as dual purpose batteries that do a bit of both. AGM batteries have the strong starting power you need to start your engine, along with enough cycling power to run additional applications. Because of this, many RV and boat owners rely on a single dual purpose battery instead of having both a starting/cranking (SLI) and deep cycle battery on board. Want to learn more about RV and boat batteries? Read our blog articles entitled “Starting, Deep Cycle & Dual Purpose: Breaking Down Your RV Battery Options” and “Which Brand of Battery is Best for Your Boat?”
Can You Charge an AGM Battery with a Regular Charger?
One important thing to keep in mind is that you can’t charge an AGM battery using a standard battery charger. This is because AGM batteries have different charging requirements than standard flooded batteries. AGM batteries require a slower, more stable charge than flooded batteries and can’t sustain the high charging speeds used by standard battery chargers.
If you charge an AGM battery with the wrong type of charger, you will end up under or overcharging your battery. Undercharging can cause sulfation on the battery’s plates, reducing its ability to accept a full charge. Overcharging cooks the components inside the battery, which can shorten its lifespan or kill the battery entirely.
When shopping for battery chargers, be sure the model you select is compatible with the chemistry and voltage of the battery you’ll be using it on. For instance, if you have a 12 volt AGM marine battery, you need a charger that works with 12 volt AGM batteries. Many modern chargers come with settings for a number of different battery types.
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