Everything You Should Know About SLA Battery Technology

Lead-acid batteries are part of our everyday life. These batteries power emergency lighting systems, cars, motorcycles, fire and security alarms, children’s toys, boats, RVs, residential and commercial backup power systems, and UPS devices. It even has many more applications. The most up-to-date technology for these types of batteries is the sealed lead-acid (SLA) battery, also known as valve-regulated lead-acid (VRLA) batteries.

The SLA battery improves the classic flooded batteries by being leakproof and being more flexible for different positions. Best of all, it rarely requires maintenance. There are many SLA battery sizes, voltages, and amperages varying on their internal design. Depending on the specs and type of sealed lead-acid battery, you may use it for different applications, which is why you must properly choose the right sealed battery type.

If you are thinking of replacing your old sealed lead-acid battery or acquiring one for the first time, it is important to have the best knowledge on the subject. Here, we will explain what an SLA battery is, how to charge an SLA battery to ensure a long life span, the different VRLA battery types, and other important information you might need to know. You will also find an FAQ section answering the most common questions about valve-regulated lead-acid batteries.

What Is an SLA Battery?

To choose the right battery for each application, it is important to learn what a VRLA battery is, how they work, and how they differ from other types of batteries.

The SLA battery uses a lead-acid or lead-calcium electrolyte in a dry or gelled state which prevents it from leaking, making it safer for many applications. These batteries are designed using lead dioxide and lead plates for the positive and negative terminals of each cell. When the battery is discharged, the electrolyte reacts with the plates, and the lead acid turns into lead sulfate and water. The opposite process occurs when the battery is charged, turning the electrolyte back into lead-acid.

To make it safer to use, the sealed lead-acid battery is manufactured using a sealed casing for each battery cell and features a valve that vents gases during rapid discharges and stressful charging periods. It is recommended to avoid repeated venting of the gases by taking proper care of the battery, especially since venting could eventually dry out the battery and render it useless.

The sealed design of the battery allows it to be installed in many orientations/positions without leaking its electrolyte. Another aspect of the valve-regulated lead-acid battery fixing a major flaw in flooded batteries is the dry state of the electrolyte, making it shock- and vibration-resistant.

SLA Battery Types

Each application might require a different battery. To know what a SLA battery is used for, we should first learn about the different rechargeable sealed lead-acid battery types. Choosing the right option will ensure you have a stable power source with an extended life span. Here are the four VRLA rechargeable battery categories.

General-Purpose Valve-Regulated Lead-Acid Battery

One of the most versatile options is the general-purpose VRLA rechargeable battery. These batteries have a stable voltage, provide a medium-high amperage, and have good cycling operations. General-purpose batteries are ideal for most electronic devices, riding toys, security systems, emergency lighting, and more. Depending on the application, you might need a 12V or 6V SLA battery.

Deep-Cycle Sealed Lead-Acid Batteries

Deep-cycle batteries are used for applications requiring a higher discharge depth for longer periods. The deep-cycle SLA AGM battery has a longer life span of up to 500 full cycles at a 50–70% depth of discharge (DOD), depending on the design. A deep-cycle 12V SLA battery is usually a perfect fit for motorizing RVs, boat trolling motors, wheelchairs, and many others.

Gel-Sealed Battery

Gel SLA battery is slightly different from the SLA AGM battery since the electrolyte is held within a silica gel instead of an absorbent glass mat. The gel valve-regulated lead acid battery makes better use of the acid within the electrolyte, enhancing the cycle and making them a better fit for marine applications, scooters, water-pumping systems, and solar generation systems.

High-Rate UPS VRLA Battery

To ensure backup power for emergency electronics, you might require a high-rate UPS AGM SLA battery. These batteries are the perfect fit for medical equipment, residential and commercial backup energy systems, data centers, and many others. Even residential and industrial UPS devices use a 6V SLA battery or a 12V SLA battery, depending on the design and power required.

What’s the Difference Between SLA Batteries (VRLA Batteries) and AGM Batteries?

When learning what a VRLA and AGM battery are, it might be entirely normal to think that they are two different things. The truth is that the SLA AGM battery is only one of the two types of valve-regulated lead-acid batteries, while the other one is the gel-sealed lead-acid battery.

An SLA/VRLA battery refers to the same technology, using two different acronyms. These acronyms refer to the valve-regulated batteries that use a regulation valve system for gas releases. This battery technology divides into gel-sealed lead-acid batteries and absorbing glass mat (AGM) lead-acid batteries, with the main difference being the type of casing for the electrolyte and some specs of the battery.

The gel and AGM SLA batteries share some common advantages since they are both SLA/VRLA batteries. Both are leak-free, resistant to vibration, resistant to shocks, and require less electrolyte. The biggest advantage of these batteries is that they combine oxygen and hydrogen within the battery, preventing water losses, except in cases of improper charging or rapid discharging when they vent gas buildup.

SLA Battery FAQ Section

Whether you are acquiring a new VRLA battery or replacing an old one, our FAQ section answers the most recurrent questions about SLA battery maintenance, proper charging, battery recycling, choosing the right battery, and more.

What’s the Life of an SLA Battery?

The life span of a sealed battery is defined by the number of cycles you can discharge and charge it within the allowed depth of discharge while maintaining its capacity. This specification may vary depending on the battery type, and its life span may vary depending on the application. Manufacturers recommend replacing batteries after losing 20% of their capacity, but you can still get some power at this point.

For instance, a quality gel 12V SLA battery properly discharged and charged back again to a 50% depth of discharge can last for around 450 cycles retaining 100% of its capacity, 600 cycles with 80% of its capacity, and 1000 cycles with 50% of its capacity. AGM valve-regulated lead-acid batteries have a shorter life span, lasting on average 200 cycles with 100% of its capacity, 250 cycles with 80% of its capacity, and up to 500 cycles with 50% of its designed capacity.

Considering these cycles, the gel VRLA rechargeable battery has an average life span of 8–10 years, while the AGM SLA battery might last around 5–6 years. To ensure a battery lasts its estimated life span and in some cases even longer, it is important to take proper care of it.

How to Extend the Life of My SLA Battery?

Extending the lifespan of a battery can be easily achieved by using a proper charging voltage and proper usage of the battery. This is why you should know the proper charge/discharge specifications set by the manufacturer of the sealed battery. Here are some tips that will help you extend the lifespan of your valve-regulated lead-acid battery.

Properly Charge the Battery

While the SLA AGM battery is more resistant to inappropriate charging than the gel SLA battery, it is important to charge both of them properly. You could do this by looking into the specifications set by the manufacturer and acquiring a special charger that ensures the proper charging voltage/current.

Use the Right Battery Type for Each Application

Choosing the proper type of battery from the four available categories for each application is important. This ensures you will not demand a higher current than recommended for the SLA battery. In turn, this extends the lifespan of the battery.

Recharge Your Battery Before Storing

Depending on the application, you might need to store your gel or AGM valve regulated batteries for some time. If you do this, it is important that you properly charge them beforehand. This ensures that even if your battery loses a percentage of its charge during the stored months, it will not get past the 50% recommended DoD.

You might also like to perform regular SLA battery maintenance by giving it a fully saturated charge once every few weeks. It is also important to operate the battery at moderate temperatures and never go past the recommended maximum DoD.

How Can I Charge My SLA Battery?

An important aspect to consider when looking to extend the lifespan of your battery is learning how to charge the SLA battery at the proper charging parameters. Doing so will ensure that your sealed lead acid battery will not overheat when fully charged, and in turn, this will extend its life span.

Recommended charging voltages depend on the SLA battery sizes and types. For instance, a deep-cycle AGM 12V SLA battery should be charged at 14.6–14.8V, while a regular AGM 12V SLA battery might be charged at 13.6–13.8V. A gel 12V SLA battery for deep-cycle uses should be charged at 14.1–14.4V, while for regular usages, it should be charged at 13.5–13.8V. To ensure proper charging parameters, we recommend acquiring a proper battery charger.

Aside from a proper voltage, sealed lead-acid batteries should be charged at a recommended amperage depending on their capacity. Charging an SLA battery at a higher amperage than the one specified by the manufacturer might cause the battery to overheat and vent gas. This will reduce its lifespan, and eventually, the battery might dry out entirely.

Charging amperage might vary depending on the battery capacity. The 45–55 Ah batteries are usually charged at 5–10 Amps. On the other hand, 65–70 Ah require a max 10–20 Amp, 75 – 85 Ah batteries are usually charged at 15 – 20 Amps, and batteries that go from 95 to 200 Ah are usually charged at 20–40 Amps, depending on their specs. We recommend you to use these parameters as guidelines since you should only use the recommended amperage by the manufacturer.

How Can I Recycle SLA Batteries?

One of the advantages of valve-regulated lead-acid batteries is that they can be recycled. When disposing of your old VRLA battery, you should properly recycle the battery to help the environment and reduce waste.

Each state provides recommendations as to where and how you should dispose of your battery for it to be recycled. Most states have regulations that impose high fines for citizens who wrongly dispose of batteries, which is why if you do not follow the proper procedure when disposing of a battery, you might get a heavy fine.

There are several companies providing recycling services that cover the whole United States. The US Environmental Protection Agency (EPA) recommends using the services of Earth911 and Call2Recycle to find the proper recycling locations for your rechargeable sealed lead-acid battery.

What Terminal Do I Need for My SLA Battery?

Just like there are many SLA battery sizes, the same happens with the battery terminals. You might need different battery terminals for cars, motorcycles, scooters, and more. Here, we will explain the most common battery terminal types and how they look.

A car starter rechargeable sealed lead-acid battery uses a cylinder post, while motorcycle ones use square posts. Both these terminals allow for the proper connection of standard cables for these types of vehicles.

Other commonly used terminals are the FASTON tabs. These are flat blades sticking up at an angle. Their size might change with their type. The most common sizes are the F1 and F2 terminals, but you could also find an F1/0 terminal.

The Nut and Bolt are other commonly used terminals for valve-regulated lead-acid batteries. These consist of a vertical blade with a cylinder in the middle. These terminals go from the NB1 to the NB5.

The threaded insert, as the name refers, is a terminal that allows for threaded wires to be inserted into the hole within the terminal. These terminals are excellent for multiple applications that require installations of batteries with naked wires that will be later covered with insulating materials.

While these are the most common choices, there are several other terminals to choose from. Other common terminals for valve-regulated lead-acid batteries include insulated wire leads, recess terminals, pressure contacts, H-type connector, S-type connector, and the spring terminal.