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Basics of VRLA Type of Batteries

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Basics of VRLA Type of Batteries

Let us introduce you to some of the basics of

VRLA Battery (Valve-Regulated lead-acid battery)

A VRLA battery is also called Sealed Lead-Acid (SLA) or Maintenance-Free Battery.In fact, "Maintenance-free" is an inaccurately used synonym of VRLA Batteries since regular cleaning and battery tests are required.

Three main types of VRLA can be found:

  • Sealed VR wet cell
  • AGM
  • GEL

VRLA and Lead-acid cells basically consists of lead plates which serve as electrodes, suspended in an electrolyte consisted of diluted sulfuric acid.

I. Wet Cell Batteries

Originally, it was this type of battery that had been used for years. However, there are drawbacks and benefits that each one of us should know when it comes down to them.


1. They contain acid in liquid form which means the liquid electrolyte is hazardous and is unsuitable for shipping. 

2. Wet cells have to maintain water levels which is the main reason why they are not categorized as "maintenance-free" but "hazardous". 

3. Flooded batteries die faster under hot conditions.

4. Excessive vibration, prolonged use and overcharging result in shortening cycle life.


1. Battery price suitable for every pocke.

2. Excellent when it comes to high-drain devices.

3. Easily replace.

4. Excellent tolerance of improper recharge voltage.

II. AGM Batteries

AGM batteries differ from wet cells, due to their electrolyte being held in the glass mats whereas, wet cells have their plates freely flooding. These thin fibers are put into a mat to increase surface area enough to hold sufficient electrolyte on the cells.The fibers composing the fine glass mat do not absorb nor are affected by the acidic electrolyte as well as the mats are wrung out by approximately 4% after being soaked in acid. interestingly enough, AGM battery plates can be in different shapes, e.g flat, bent, rolled. AGMs are built in a rectangular shape to fit BCI battery groups and are designed to perform better in contrast to conventional batteries. 

III. GEL Batteries

Originally a kind of gel cell was produced in the early 1930s by adding silica to the sulfuric acid. By this time the glass case was being replaced by celluloid and later other plastics. A modern GEL cell is a VRLA battery which mass is gel alike and immobile. Some of the main benefits are:

  1. Can be kept in any position (vertical/horizontal).
  2. Reduce spillage (common to wet cell batteries).
  3. Boast greater resistance to shock and vibration.
  4. Prolonged Battery life.

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