Sealed Lead Acid Battery: What to Know?

Sealed Lead Acid Battery: What to Know?

Here is a complete guide to sealed lead acid batteries, you can learn their pros and cons, and how to store and maintain your sealed lead acid batteries.

A lead acid battery with the sulfuric acid electrolyte coagulated (thickened) to prevent spilling is known as a sealed lead acid battery or gel cell. Although they have vents, they are only partially sealed in case gases are unintentionally released, such as through overcharging.

You can find out more about sealed lead acid batteries by reading this blog.

Further Reading:

What Exactly is a Sealed Lead Acid Battery?

An original name for a sealed lead acid battery was a VRLA battery or a valve-regulated lead acid battery. These batteries are 100% rechargeable and based on a lead-acid design. These batteries are designed to be maintenance-free (do not require the user to add water to the cells), and spill-proof. No matter how the batteries are mounted, they will still work to their full potential without leaking any acid.

You might be wondering how the valve-regulated component of the sealed lead-acid battery functions. An exclusive safety release valve is built into every Sealed Lead Acid battery. When the Sealed Lead Acid battery begins to build up gases, these valves act as an emergency pressure release system and open.

During a period of an extremely high rate of charge (extreme over-charging), gases will be generated inside the battery that could potentially build up to critical levels and force their way out – via exploding a side of the battery or a simple crack in one of the cell dividers. All Sealed Lead Acid batteries feature these tiny pressure-release valves as part of their design to avoid this scenario.

Sealed Lead Acid Battery: What to Know?


  1. Lower cost of acquisition.
  2. No part replacement.
  3. Sealed Lead Acid batteries don’t experience the memory effect, so they don’t need to cycle as frequently as nickel-cadmium batteries do. So there will be less downtime.
  4. AGM batteries don’t need to be filled with water because gases combine again.
  5. There is no threat of “Thermal Runaway” and therefore overtemperature detection systems are not required.
  6. As good as or better than nickel-cadmium in cold weather performance.
  7. According to independent laboratory testing and compliance with DOT shipping requirements for hazardous materials, 49 CFR Section 173.159, sealed lead acid batteries are not considered to be dangerous. They can be shipped without restriction.
  8. 100% recyclable.


  1. shorter lifespan than lead acid floods.
  2. Concerned about being overcharged.

Sealed Lead Acid Battery Construction

The most popular kind of storage battery is the sealed lead acid battery, which is well-known for its many uses in things like UPS, cars, medical equipment, and telecommunications. The battery is made up of cells, each of which consists of plates submerged in a solution of diluted sulfuric acid as an electrolyte. The construction of the lead acid battery is illustrated below.

Sealed Lead Acid Battery: What to Know?

Battery Terminals

AMP Faston-type terminals made of tin-plated brass, post-type terminals of the same composition with threaded nut and bolt hardware, or heavy-duty flag terminals made of lead alloy are all options for battery terminals, depending on the model. As a sealing substance around the terminals, a special epoxy is employed.

Read More: How Do Lead-acid Batteries Work?

Battery Plates (Electrodes)

The small amounts of calcium and tin in the grid alloy give the plate strength and ensure durability even under heavy cycle use. The grid is mixed with lead dioxide paste to create the electrically active substance.

The paste on the negative plate is pure lead in the charged state, while the paste on the positive plate is lead dioxide. To maximize surface area and thereby capacity, both of these have a porous or spongy form. In both cyclic and float applications, the heavy-duty lead calcium alloy grids offer an additional performance and life margin and offer unmatched deep discharge recovery.


Sulfuric acid in the immobilized form: H2S04.

Battery Relief Valve

In case of excessive gas pressure build-up inside the battery, the relief valve will open and relieve the pressure. The one-way valve serves as both an essential safety device in the event of excessive overcharging and ensures that no air enters the battery, where the oxygen would react with the plates and cause internal discharge. Neoprene rubber makes up the seal ring, and the vent release pressure ranges from 2 to 6 psi.

Sealed Lead Acid Battery: What to Know?

Different Types of Sealed Lead Acid Batteries

There are two different types of Sealed Lead Acid batteries out on the market today – AGM, and GEL batteries. AGM batteries use a unique plating procedure that maximizes the amount of electrolyte that reaches the lead plates of the battery. AGM, or absorbed glass mat, is the abbreviation for what the entire procedure entails.

Between the battery’s internal lead plates is a mat made of incredibly fine glass fibers that have been woven together. For the duration of the battery, this glass mat can absorb and hold the ideal volume of electrolyte between the plates. By using less electrolyte, this technology improves battery performance and power.

Read More: Are AGM Batteries Better Than Lead-acid?

The infamous GEL battery uses a special gel-based mixture in place of the typical electrolyte present in the common flooded lead acid batteries (think car batteries), which is frequently confused with AGM Sealed Lead Acid batteries.

In this instance, the gel is made by mixing silica fume with regular sulfuric acid to form a special kind of gelified electrolyte. This design enables the battery to suffer much less internal corrosion, thus increasing the overall life of the battery – assuming you take care of it properly.

How Long Does An Sealed Lead Acid Battery Last?

The life of a Sealed Lead Acid battery will depend on a number of factors, including what it’s being used for, the operating temperature, and how well it’s been maintained. Cycles of charging are used to gauge battery life.

A single charging cycle refers to the process of going from the battery’s full charge capacity to a complete discharge. A Sealed Lead Acid battery should last between 50 and 500 charging cycles as a general rule.

How Do You Maintain A Sealed Lead Acid Battery?

It goes without saying that you’ll want your battery to last as long as possible. Your charging habits play a big role in whether you can accomplish that. Make sure you’re using the appropriate charger first, of course.

A different charge voltage is needed for gel batteries than for other sealed lead acid batteries in solar, wind, and communications applications. Make sure the charger you choose is rated for the specific voltage of your battery.

Be careful not to overcharge your battery. In an effort to charge your battery more quickly, avoid increasing the voltage or charging time. Overcharging causes your battery to overheat, which can kill it in just a few hours.

Undercharging is equally problematic. Do not use a lower charging voltage than your battery requires as this will prevent your battery from becoming fully charged. A battery’s lifespan is shortened when it is undercharged because it must work harder than when it is fully charged.

Sealed Lead Acid Battery Charging & Storage Tips

Follow these suggestions to maintain a regular charge and keep your Sealed Lead Acid battery healthy.

Sealed Lead Acid Battery: What to Know?
  • Recharge your battery after each use
  • Always store your battery fully charged
  • Disconnect the charger immediately once the battery is fully charged
  • When storing a Sealed Lead Acid battery, be sure to keep it in a cool, dry place
  • Do not store a Sealed Lead Acid battery in a discharged state
  • When storing a battery, check its charge every couple of months
  • If the battery is stored in an area with a temperature above 68 degrees F, it will need to be charged more frequently

Further Reading: How Do You Charge a Lead-acid Battery?

What’s the Difference Between Flooded Lead Acid and Sealed Lead Acid Batteries?

Sealed lead acid batteries don’t require maintenance and they’re cheaper than flooded lead acid batteries.

Sealed lead acid batteries are called Valve Regulated Lead Acid (VRLA) batteries because they have valves that release gas if pressure builds up. This happens as the battery recharges. The valves eliminate the problem of gassing that a flooded lead acid battery has.

A boosting equalizer is not necessary for sealed batteries. A flooded lead acid battery’s capacity is decreased by sulfation, which is avoided by using an equalizing boost.

Sealed lead acid batteries also don’t “dry out” so you don’t need to add water to them as you do with flooded lead acid batteries. Instead sealed lead acid batteries combine oxygen and hydrogen to create water. The battery no longer needs to be watered as a result.

A sealed battery recharges more quickly than a flooded lead acid battery because calcium is added to the plates to lessen water loss. There are two ways that sealed lead acid batteries keep water inside. A gel or absorbent fiberglass separators are both used. The two types of sealed lead acid batteries, absorbent glass mat (AGM) and gel batteries, are produced in this manner.

Conclusion: Sealed Lead Acid Battery

For a battery backup system for load shedding and blackouts, sealed lead-acid batteries are ideal. They are less expensive and require no upkeep. They are also perfect for off-grid homes, especially those that are only occupied occasionally.

A well-maintained sealed lead acid battery will always outlive one. However, a poorly maintained flooded lead acid battery won’t last as long as a sealed lead acid battery that doesn’t need maintenance.


Is Sealed Lead Acid Battery the Same as AGM?

Unlike conventional lead-acid batteries, AGM batteries provide better cycling performance and faster charging performance. AGM batteries exhibit minimal acid leakage and gassing, last longer, and are not susceptible to freezing.

How Often Should You Charge a Sealed Lead Acid Battery?

Start the day fully charged: Lead acid batteries should be charged every day after 15 minutes or more of use. The device must be plugged in and charged overnight until the charger indicates that the batteries are fully charged the following day before use.

Do Sealed Lead Acid Batteries Need Maintenance?

Because of the design of a Sealed Lead Acid Battery, these batteries require less maintenance than Wet Cell battery systems. For a Sealed Lead Acid Battery system, maintenance should be done at least once every six months, while a Wet Cell Battery system should have it done at least once every three months.

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