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Home / Tutorial & Guides / Guide to Buying SLA Batteries

Guide to Buying SLA Batteries

SLA batteries, also known as sealed lead-acid batteries, are rechargeable and widely used in backup power systems, medical devices, and UPS. They require no maintenance, making them a popular choice for many applications. They are also versatile, durable and cost-effective.

There will eventually be a time when you’ll need to buy a battery for a device or purchase a replacement battery. We’ve put together a list of things you might need to look at when you’re in the market for a replacement SLA battery.

Basics of SLA Batteries

SLA batteries (also known as Sealed Lead Acid batteries) are rechargeable batteries that use lead plates and sulfuric acid as an electrolyte. They are commonly used in backup power systems like UPS devices and generators, as well as wheelchairs and scooters that require reliable power. It’s important to understand that there are several types of SLA batteries.

AGM or Absorbent Glass Mat batteries. These are best for applications that require high power density.

Gel Batteries use a gel electrolyte and are suitable for deep cycle applications requiring high capacity and long life.

VRLA or Valve Regulated Lead Acid batteries use a pressure-relief valve to regulate the internal pressure and prevent overcharging. They are low maintenance.

Deep Cycle batteries are designed to provide a steady charge over a long period of time and are suitable for marine and RV use. 

High Discharge batteries (often referred to as SLI batteries) provide a high current discharge over a short period of time and are best suitable to starting motors.

When looking for a type of replacement battery, consider its use. Mostly you’ll be looking to choose the same type that is currently in use or go with the recommended type.

Size and Capacity

The size of a replacement SLA battery is important usually because there is limited room where the battery is housed. If the battery is a different size, it may be impossible to fit into the allotted space without some significant reworking. The specs usually include the battery size with length x width x height so make sure to measure and choose one with the same dimensions.

Voltage is a unit of power that is always used with SLA batteries. Typically, you’ll notice 6V or the more common 12V for most of your equipment and in some cases 24V.

The amp rating is also important. The amps of an SLA battery are commonly expressed in terms of the battery's amp-hour (Ah) rating, which is a measure of the battery's capacity. The Ah rating of an SLA battery is a measure of how many amps the battery can deliver over a certain period. For example, a 12V 7Ah battery can deliver 7 amps for one hour, or 1 amp for 7 hours. The higher the Ah rating, the longer the battery can deliver power to a device.

NOTE: Make sure to consider the terminals of the replacement batteries. Again, you want to make sure they match the current battery.

When looking to replace your SLA batteries, finding one with the same voltage and amp rating is recommended to avoid damaging equipment.

Brand Quality

There are plenty of brands to consider for SLA batteries and not all are created equal. Some brands may have a strong name and as a result will often add a considerable amount to the price. Conversely a lesser-known brand may provide a cheaper product but perhaps with poor reviews. Given the availability of reviews on most websites, there is usually enough information available to determine the quality of a battery and the company behind it. Do your due diligence to prevent any unwanted surprises.

The ability to search online has made it much easier to find an appropriate replacement as well as to comparison shop for pricing.


There are a few things to consider when charging a battery. Make sure you have the correct voltage charger. A 6V for a 6V battery, a 12V for a 12V battery etc. One thing to note is that if you have 2 12V batteries connected, you should use a 24V charger or charge them separately. Don’t overcharge. The general rule for charging your battery is Amp hours multiplied by 1.3 then divided by the charger Amps.

Float charging is a common term in SLA batteries because of the nature of their roles. For things like UPS devices, generators, exit lights, these are all essentially on standby mode for long periods of time. They have a steady low voltage charge aimed at keeping its life expectancy much higher.

A high-rate SLA battery is the opposite of float charging in that they provide a high burst of power for a short period of time. In this instance, the more you discharge the shorter their lifespan. Depending on how often you use them, their lifespan may be much longer.


Installing a replacement SLA battery should be relatively easy. Essentially look to match the previous configuration and connections.

  • Check the connections to make sure they are free of dust, dirt and debris.
  • Place the new battery in the allotted housing.
  • Reconnect the cables based on the previous configuration

We have a series of installation guides depending on your product needs so feel free to check those out.


Even though SLA batteries are generally safe because they are sealed, there are still some things you may want to consider. Always with SLA batteries handle carefully and inspect closely. Look for things like swelling or leaking. Do not install if anything looks off. Gloves and goggles may be a good idea especially if the battery is defective. Remove jewelry and watches, again just in case there are issues. Keep your sleeves out of the way, they can sometimes get caught up during installation or torn on some of the cables or connections.

Types and Uses of SLA Batteries

Another important factor to consider when buying SLA batteries are the types of SLA batteries and matching those with what they will be used for. As an example, if you’re looking for a battery for a travel trailer, you’re going to want to get a deep cycle battery that is suited for longer sustained amount of power. You’ll generally find three types of SLA batteries, Deep Cycle, SLI and Dual Purpose batteries.

Deep Cycle Batteries  - are designed to be charged and recharged regularly and hold a sustained amount of power. They are best for travel trailers, RV’s, marine vehicles and golf carts. They help to power accessories like lights on a boat.
SLI Batteries – the acronym stands for Starting, Lighting and Ignition so they’re suited best for short bursts of power, particularly for starting an engine like in motorbikes, snowmobiles, ATV’s and other powersports equipment.
Dual Purpose Batteries – these are able to accommodate both the role of starting an engine and maintaining a long charge. Boats often use these as well as RV’s and can be a great option to reduce weight or save money.

SLA Battery Terms

Part of the challenge of buying an SLA battery is getting around all the technical terms associated with them. Our website lists many of them under the “Specs” tab and terms like Voltage and Dimensions can be a little more obvious than Cold Cranking Amps or Terminal. For most if you are looking at a replacement SLA battery, typically just match the specs that are listed on the current battery and you’ll be fine. Other terms like Exact OEM Replacement simply means that it should be compatible with the manufacturers models and others like Maintenance-Free and Factory Activated are unique features of SLA batteries and are self descriptive. We do offer a more comprehensive guide of SLA Battery Technical Terms.


When you do finally purchase and install your replacement SLA battery, what do you do with the old one? A little-known benefit of SLA batteries is that they can be recycled, in fact most of its components can either be melted down and reused, or in the case of the lead and sulfuric acid, be used again and again. The EPA notes that SLA batteries are among the most recycled products in the country at around 99%. They can often be dropped off at specific recycling centers or some big box store locations so it’s also convenient.


These days buying a replacement SLA battery is a fairly easy process with the addition of websites like our own that offer affordable and quality replacements at much better rates than the original manufacturers. Many of the specs are clearly listed on the casing so finding something that matches is a lot clearer. Our own Tutorials & Guides section hopefully helps to clarify some of the more obscure and complex things that can often be found when purchasing a replacement SLA battery but understanding the basics of the batteries, key things to look for including potential hazards, correct handling and installation as well as charging techniques and using a company you can trust can go a long way to ensuring a positive replacement battery experience.