Lead-Acid vs. Gel vs. AGM Batteries
Lead-acid batteries are the most common in the market.
But, there are several variations of lead-acid batteries, including:
- Sealed. These are also called valve-regulated lead-acid (VRLA) or sealed lead-acid (SLA) batteries
Usually, when talking about lead-acid batteries, people mean flooded lead-acid.
Whereas, gel and AGM batteries are types of sealed batteries.
So Is a Gel Battery Lead-Acid? And Are AGM Batteries Lead-Acid?
The answer to both questions is yes.
To recap, AGM, gel, and flooded batteries are all types of lead-acid batteries.
For the most part, the contents and electrochemical workings of these lead-acid batteries are very similar.
But there are some important differences, which we’ll cover next.
What’s the Difference Between Flooded and Sealed Batteries?
The main difference between flooded batteries and sealed batteries is the electrolyte.
Flooded batteries are filled with a liquid electrolyte solution.
On the other hand, sealed batteries have a solid electrolyte.
AGM batteries are filled with a glass mat substance.
And gel batteries are filled with silica to coagulate the electrolyte.
Besides that, sealed batteries are virtually immune from spills and leakage.
As a result, they can be used in any position or orientation without worry.
But flooded batteries are not sealed and thus liable to spills and leakage.
Furthermore, they require regular watering.
Conversely, sealed batteries do not.
And that makes them virtually maintenance-free.
What Are Flooded Batteries?
Invented in 1860, rechargeable flooded lead-acid batteries are the most common and widely used type of lead-acid battery.
Flooded batteries are composed of alternating lead and lead oxide plates along with liquid electrolytes (sulfuric acid and water).
Using an electrochemical process, these components react to produce energy.
How Do Flooded Batteries Work?
First, they are called “flooded batteries” because the liquid electrolyte is free to move within the cell.
What does that mean?
Inside the cell, the alternating lead plates are immersed in the electrolyte solution.
As the electrical current passes through the battery, the electrolyte interacts with the lead plates.
The plates are then converted into lead sulfate.
And it’s through this reaction that chemical energy is converted into electrical energy.
But this process is reversed once the battery is charged.
The charging breaks down the lead sulfate, turning it into pure sulfuric acid and lead.
Also, the water in the electrolyte splits, and hydrogen gas is released.
So, to prevent the hydrogen gas build-up (and avoid battery explosions), flooded batteries have a vent to exhaust the gas and relieve the pressure.
But this process also leads to water loss.
That’s because the hydrogen doesn’t have a chance to recombine with oxygen and settle back into the electrolyte solution as water.
Thus, it creates a need to regularly water the battery.
This process is why, although they are the cheapest, flooded batteries require more battery maintenance.
The user must access individual cells and top them up using distilled water as the battery dries out.
Flooded Battery Advantages
- Widely available
- Relatively cheap
- Available in different sizes and capacity
- Provides good deep-cycle performance
Flooded Battery Disadvantages
- Requires regular watering and strict maintenance
- Requires charging in designated and ventilated rooms
- Liable to cause injury and corrosion due to spills and leakage
- Requires the use of personal protective equipment (PPE) when handling
- Vents out substantial quantities of flammable hydrogen gas
- Easily damaged if left to over-charge
- Prone to high self-discharge rate
- Considered hazardous material when transporting
What Are Flooded Batteries Used For?
Large flooded batteries are often used in industrial equipment, like forklifts.
Additionally, they’re a popular solution for cars, solar power energy, and uninterruptible power supplies (UPS).
What Is A Gel Battery?
Before you can determine the pros and cons of a gel battery and how they will affect you, it’s important to understand what exactly a gel battery is. A gel battery is very similar to a traditional lead-acid battery with the addition of silica to the electrolyte to create the gel like substance.
A gel battery is a maintenance-free, valve-regulated, sealed lead-acid (SLA) battery.
First conceived in the 1930s, gel battery technology wasn’t perfected and commercialized until the 1980s.
This thickening of the electrolyte means that gel batteries can be installed in a variety of positions and don’t emit as many fumes.
Pro Tip: This allows for gel batteries to be used in applications where ventilation is limited.
How Does It Work?
A gel battery (often referred to as a gel cell battery) is a lead-acid battery that is valve regulated. When the electrolyte is mixed with sulphuric acid and silica, it becomes a relatively stationary gel substance.
This gel mixture allows the battery to utilize the acid and electrolyte in the same way it would with a traditional lead-acid battery, just without the added maintenance.
- Maintenance Free: Because the batteries are comprised of gel instead of liquid, there is little to no maintenance to keep the battery working properly.
- No Leaks: Even though wet cell batteries are sealed in a plastic encasement there is still the chance that it will leak. Gel batteries are also sealed but with a valve that removes excess pressure. This means that between the gel substance and the removal of pressure, there is nowhere for the mixture to go.
- Install Them Anywhere: Gel batteries have the advantage of being able to be used in virtually any position, because they don’t leak and are generally maintenance free. This greatly increases the number of applications gel batteries can be used for.
- Minimal Risk: When damage occurs to a traditional lead-acid battery you are faced with a massive and dangerous clean up (not to mention the impact on anything the battery acid may come into contact with during the process). Gel batteries will not leak out if the casing becomes damaged, so there is a reduced risk of harm coming to the equipment and clean up hazards.
- Vibration Resistant: One of the biggest complaints with wet cell batteries is that they are very susceptible to extreme vibration and other impacts. Gel batteries absorb the impact and vibrations, making them great batteries for items such as four wheelers.
- No Fumes: Because these batteries are comprised of a gel substance there are minimal fumes created as a result of use. This means that there is a reduced need for ventilation which increases the potential applications gel batteries can be used for, as well as making them easier to charge anywhere.
- Resistant To Discharge Death: When using a wet cell battery it’s important that you don’t allow the battery to discharge too much. Otherwise, it will never recharge. Gel cell batteries aren’t that way. They are deep cycle batteries which means that they can discharge more and still be recharged like new.
- Offer more resistance to extreme temperatures
- Classified as non-hazardous materials for road transportation
- Offers extremely low self-discharge rates
- No gassing, making them safe to install in places with limited ventilation
- They do not experience corrosion
- Can be installed or used near sensitive electronic equipment
- What Are Gel Batteries Used For?
Gel batteries are used in low power demanding equipment like:
- Floor scrubbers and sweepers
- Walkie pallet jacks
- Cell phones
How Long Can a Gel Battery Last?
The answer to this question depends on:
- How it’s charged
- How it’s used
- The working temperature
- The charge capacity
If you charge a normal 12-volt gel battery to 90% charge capacity and keep it unused in the charged state, it will last up to 6 years and while retaining up to 80 % of its original capacity.
Now, what is the life expectancy of a gel battery?
Gel batteries can last up to 20 years with up to 5,500 charge cycles.
Compared to flooded batteries’ 1,000 to 1,500 charge cycle (3 to 5 year) lifespan, that’s much longer.
And that’s because gel batteries resist sulfation and are maintenance-free.
Charging Gel Batteries
Charging gel batteries is a little more complex than charging flooded lead-acid batteries.
Here’s what you need to know…
You’ll first need a specialized gel battery charger (or SMART charger).
Because gel batteries are susceptible to voltage spikes.
And these specialized chargers have specific settings that prevent these spikes.
Secondly, when charging a gel battery, you need to give it extra time.
That’s because gel batteries require slow, constant voltage charging cycles.
And charging the battery at the wrong voltage can damage it, cause battery failure, or shorten its lifespan.
Third, you’ll need to constantly monitor the charging process and take off the charger as soon as charging is complete.
If you don’t, you can create pockets in the electrolyte.
And this can cause irreversible damage to the battery.
Can You Charge a Gel Battery With a Regular Charger?
Yes, you can.
But, charging gel batteries with a flooded lead-acid charger is risky.
Gel batteries like to be charged slow and low.
So, when charging a gel battery with a lead-acid charger, you must be extra cautious.
Ensure that the peak charging voltage does not exceed 14.7 volts.
Otherwise, you can end up with a dried-out, non-conductive gel.
How to Charge a Gel Battery With a Regular Lead-Acid Charger
Attach the lead-acid battery charger to your gel cell battery. Ensure you connect the terminals correctly. The red cable goes to the positive terminal. And the black cable goes to the negative terminal
Switch the charger settings to deep cycle (for example, to 2 amp /12 volt). This will help mimic the charging characteristics of a constant voltage charger (CVC) that is used to charge deep cycle gel batteries
Next, switch the charger to manual instead of auto. If you leave it on auto, it may taper its voltage when the battery reaches full charge
Now, monitor the battery closely as it charges for 7 to 12 hours. Make sure the voltage output never exceeds 14.7 volts
Once the battery charging reaches 95%, remove the charger
What Are AGM Batteries?
AGM (or absorbed glass mat) is a type of sealed lead-acid battery.
AGM batteries were invented in the late 1970s for use in military aircraft, traffic signals, telecommunications systems, and other devices.
But they were not used commercially until the mid-1980s.
How Do AGM Batteries Work?
First, the composition of AGM batteries looks likes this:
- Fiberglass mats
- Lead plates
- Pressure control valve
The microfibre fiberglass mats, placed between the lead plates, absorb and immobilize the electrolyte.
The glass mats also act as separators and insulators between the positive and negative plates.
This design is what makes AGM batteries spill-proof.
Like gel batteries, AGM batteries are recombinant.
What does this mean?
The safety pressure relief valve prevents the release of hydrogen and oxygen gases.
Instead, they’re able to recombine during charging.
And this helps prevent subsequent water evaporation from the cells.
Also, the glass mats wrapped around the battery’s positive plate help prevent damage from vibration and impacts.
They also help extend its cycling.
Plus, AGM batteries have a lower internal resistance.
This lower resistance reduces losses to heat as power flows through the system.
And that’s why AGM batteries have more output voltage and lower charging times.
AGM Battery Advantages
Sealed, allowing gasses to recombine and eliminating the need to add water
- Spill- and leak-proof design. There’s no mess while charging and no corrosion risks
- Impact-resistant and greater vibration resistance, reducing battery failures
- Superior cold-weather performance
- Well suited for high current applications
- Little internal resistance for more power output. That means less charging time and reduced losses due to heat
- Not considered hazardous material
- Do not require ventilation
- Flexibility to mount in any position or orientation
What Are AGM Batteries Used For?
AGM batteries can be used in many of the same applications as gel batteries.
Some popular uses include:
- Solar power
Are All AGM Batteries Deep Cycle?
No, not all AGM batteries are deep cycle.
But many are.
After all, they do have a greater ability to deep cycle discharge.
In fact, AGM batteries’ specified depth of discharge (DoD) stands at 80% compared to the 50% DoD of flooded batteries.
Moreover, they can charge up to 5 times faster than flooded batteries.
Do AGM Batteries Last Longer?
An AGM battery can generally last between 3 and 5 years and up to 8 years if the battery is used properly.
That’s about two to three times longer than a flooded battery.
But overall, their lifespan depends on several factors, including:
- How it’s charged
- How it’s used
- The working temperature
If these items are done improperly, that will shorten the battery’s useful life.
Are AGM Batteries Better Than Gel Batteries or Flooded Batteries?
The fact is, AGM batteries are better than flooded batteries – if you’re prepared for the extra cost.
However, they are comparable with gel batteries.
Despite their different composition, both offer benefits like:
- Better charge capacity
- Prevention of spillage and leaks
- Better electrolyte volume
- Superior life expectancy
- No maintenance requirements
Overall, the debate between AGM vs. gel batteries comes down to your budget, needs, and what serves you best.
Gel or AGM: Which is better?
From a theoretical point of view, the answer is simple: gel is the superior of the two technologies. However, if you look at it from a practical point of view, the price tag of gel batteries is only justified if the battery has to be good at withstanding jarring or vibration.
The use of gel batteries is quite prevalent in the industry of performance vehicles—off-roading bikes, jet skis, ATVs (All Terrain Vehicles), quad bikes, etc.—areas where jarring and heavy vibrations are commonplace. For applications like these, choosing gel batteries over AGM and FLA units is a sensible decision.
However, when it comes to most other applications, such as emergency lighting, regular automobiles, emergency lighting systems, and solar energy storage solutions, AGM batteries are the better choice due to their lower costs.
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