Lead Acid Battery Types Explained – SLA, AGM, GEL


This article will explain different lead acid battery types like SLA battery, AGM battery and Gel battery. SLA and VRLA are different acronyms for the same battery, sealed lead acid, or valve regulated lead acid. This battery type has the following characteristics: maintenance-free, leak-proof, and location-insensitive. This battery has a safety vent that can release gas when the internal pressure is too high. AGM, Absorbing Glass Mat refers to a specific type of SLA/VRLA in which the electrolyte is absorbed into the separator between the plates composed of sponge-like fine glass fiber mats.

Lead Acid Battery Types – 5 common battery types

Since there are many different types of batteries on the market, it is difficult to choose the right type for your application. We recommend that you take a moment to learn more about the 5 most common battery types.

1. Flooded Batteries

This is the traditional engine start, tractor and deep cycle battery. The liquid electrolyte can move freely in the battery compartment. Users can access individual batteries and can add distilled water when the batteries are dry. Popular uses are engine starting and deep cycle design.

For this type of battery, the typical absorption voltage range is 14.4 to 14.9 volts; the typical floating voltage range is 13.1 to 13.4 volts.

Flooded batteries are common in many applications, such as car start batteries, motorcycle batteries, ATV batteries, golf cart batteries, and flooded batteries for solar and emergency backup systems.

2. Sealed Batteries

This term can refer to many different structures, including slight modifications to the submerged style. In this case, even if the user cannot enter the battery compartment, the internal structure is still basically the same as the flooded battery. The only difference is that the manufacturer has ensured that there is a sufficient amount of acid in the battery to maintain the chemical reaction under normal use throughout the battery warranty period. Other types of lead-acid batteries are also sealed, as described below. Very popular uses are engine start and limited start/deep cycle applications.

For this type of battery, the typical absorption voltage range is 14.2 to 14.7 volts; the typical floating voltage range is 13.1 to 13.4 volts.

3. VRLA Batteries

This represents a valve-regulated lead-acid battery. This is also a sealed battery. The valve adjustment mechanism allows hydrogen and oxygen to escape safely during the charging process.

For this type of battery, the typical absorption voltage range is 14.2 to 14.5 volts; the typical floating voltage range is 13.2 to 13.5 volts.

VRLA batteries are common and found in many applications, such as medical mobile scooter batteries and toy and alarm batteries.

4. AGM Batteries

The absorbing glass mat structure allows the electrolyte to be suspended close to the active material of the plate. Theoretically, this improves the discharge and recharge efficiency. In fact, the AGM battery is a variant of the sealed VRLA battery, just a more advanced design. Popular uses include high-performance engine starting, power sports, deep cycle, solar and storage batteries.

For this type of battery, the typical absorption voltage range is 14.4 to 15.0 volts; the typical floating voltage range is 13.2 to 13.8 volts.

AGM batteries are very common and can be found in many applications, such as RV batteries, marine batteries, motorcycle batteries, ATV batteries, and UPS and telecommunications batteries for generators.

5. GEL Batteries

Gel batteries are similar in style to AGM batteries because the electrolyte is suspended, but the difference is that, technically speaking, AGM batteries are still considered wet batteries. The electrolyte in the gel battery contains silica additives, which can make it solidify or harden. The charging voltage of this battery is lower than other types of lead-acid batteries. In terms of the adverse effects of overvoltage charging, this may be the most sensitive battery. Gel batteries are most suitable for very deep cycle applications and may last longer in hot weather applications. If an incorrect battery charger is used on the gel battery, poor performance and premature failure are certain. Battery chargers with gel profiles will provide information on gel compatibility on the device or in the manual.

For this type of battery, the typical absorption voltage range is 14.0 to 14.2 volts; the typical floating voltage range is 13.1 to 13.3 volts.

A note about gel batteries: When referring to sealed, maintenance-free batteries, it is common for individuals to use the term gel battery, just like Tempo when referring to facial tissues or “Xerox machine” when referring to copy machine. Be very careful when specifying chargers. Normally, what people think of as a gel battery is actually a sealed, maintenance-free VRLA or AGM type battery. Learn more about the differences between gel batteries and AGM batteries.

Gel batteries are not as common as AGM batteries, but they often appear in deep discharge situations, such as wheelchair and medical mobile batteries, trolling machine batteries, and RV deep cycle batteries.

The different behaviors of AGM and GEL batteries can be attributed to different electrolyte fixation.


From the user’s point of view, AGM batteries, out of 5 lead acid battery types, are a good choice for low-cost UPS batteries with an expected life span of 5 to 10 years. For applications with an expected life of more than 10 years, gel batteries are a better choice. The flat GEL type is used for high current discharge, and the tubular plate type is used for one hour or longer discharge. This allows selection for different applications and environmental conditions. Not only should the battery life be evaluated, but the key nature of the site should also be considered, that is, the cost of removing the site from an open circuit should be considered. For all high-cycle applications (solar energy, load balancing, etc.), gel batteries are most suitable.

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