What exactly is a Valve Regulated Lead Acid battery?
Posted by Andy Hill on
Lead acid batteries come in all shapes and sizes, and one of the most common types available is a VRLA battery. They are most often found in smaller applications and are a versatile and reliable power supply, if they are properly looked after. We are going to look at what a VRLA battery is and what you can do to help maximize the performance and lifespan of these handy, and flexible, power supplies.
WHAT IS A VRLA BATTERY?
Firstly, VRLA stands for Valve Regulated Lead Acid, and are also referred to as a sealed lead acid or SLA battery. They are created by using a limited amount of electrolyte which is absorbed in a plate separator or formed into a gel. There is a proportioning of the negative and positive plates so that oxygen is recombined within the cell, with a relief valve that retains the battery contents independent of the position of the cells.
ARE THERE DIFFERENT TYPES OF VRLA BATTERIES?
Yes, there are three main types of VRLA batteries, a sealed valve regulated wet cell, AGM and gel. Gel cells add silica dust to the electrolyte, forming a thick gel. These can sometimes be referred to as silicone batteries. AGM batteries, which stands for absorbed glass mat, feature a fiberglass mesh between the battery plates that contains the electrolyte.
HOW LONG HAVE VRLA BATTERIES BEEN AROUND?
Quite a while! The very first lead acid gel battery was invented by Elektrotechnische Fabrik Sonneberg in 1934. The more modern version, closer to what is seen today, was invented by Otto Jache of Sonnenschein in 1957. The first AGM cell was patented by the Gates Rubber Corporation in 1972.
ARE VRLA BATTERIES MAINTENANCE FREE?
In comparison to traditional flooded lead acid batteries, like the ones used in forklifts and pallet trucks, yes they are, but that doesn’t mean you can neglect them. They don’t need vrla monitoring or watering in quite the same way as non-vrla batteries do. However, they should always be kept clean, using an industrial cleaner and degreaser to keep the connectors and terminals free from any corrosive elements. They should periodically be checked for both charge and functionality to keep them performing correctly.
HOW LONG DO VRLA BATTERIES LAST?
VRLA batteries are typically available with a design life ranging from 3 to 10 years but as with all lead acid batteries, their maximum life depends on how well you look after them. The single biggest killer of VRLA batteries is over-discharge. If you leave a VLRA battery, of any kind, in a chronically over discharged state, then hydration occurs. Hydration is when the lead and lead compounds of the plates dissolve in the water of a discharged cell and form lead hydrate, which is then deposited on the separators. When the cell is recharged, multiple internal short circuits occur between the positive and negative plates. Once hydration is evident, the cell is permanently damaged. You can’t see if hydration has happened because the containers are opaque and hydration can occur after just one major over-discharge event. To make sure you get the maximum amount of cycle out of a VRLA battery, and to avoid over-discharge events, you should use a low voltage alert which gives visual and audible alerts when a VRLA battery is about to be critically over-discharged.
ARE VRLA BATTERIES BETTER THAN FLOODED LEAD ACID BATTERIES?
It all depends on the application, there are pro’s and con’s to the different types of lead acid batteries. AGM and gel VRLA batteries:
- Have shorter recharge time than flooded lead–acid batteries.
- Discharge significantly less hydrogen gas.
- AGM batteries are by nature, safer for the environment, and safer to use.
- Can be used or positioned in any orientation.
- Relatively maintenance free with no vrla monitoring required.
But they also:
- Cannot tolerate overcharging: overcharging leads to premature failure.
- Have shorter useful life, compared to properly maintained wet-cell battery.
- Have a lower energy density.
- Cost more than a flooded lead acid counterpart.
So, there you have it, VRLA batteries in a nutshell. These handy power sources have a huge impact across lots of different applications, from industrial to leisure. If they’re looked after properly and protected from over-discharge, they are one of the most reliable and cost-effective methods of energy storage available on the market today.
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