VRLA Battery Guide

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Valve Regulated Lead Acid (VRLA) Batteries are low maintenance sealed lead-acid batteries. They limit inflow and outflow of gas to the cell – thus the term “valve regulated”. VRLA batteries are unique due to the fact that they contain a “starved” electrolyte (acid), which is absorbed or immobilized in a separator.

Electrolytes are commonly absorbed or immobilized in two ways:

Absorbed electrolyte: a highly porous mat made from microglass fibers is partially filled with electrolyte, acting as a separator. Also called AGM for Absorbed Glass Mat.

Gelled electrolyte: Fumed silica is hardened into a gel that free-floats in its container. During charges, the gel dries more creating cracks and fissures develop between the positive and negative. Often referred to as Gel Cell.

Advantages:

·         Maintenance-free

·         Moderate Life

·         High-rate capacity

·         High charge efficiency

·         No “memory effect”

·         State of charge can be determined by measuring voltage

·         Relatively low cost

·         Available in a variety of sizes and voltages from single cell units (2V) to 48V or higher

Disadvantages 

·         Cannot be stored in discharged condition

·         Relatively low-energy density

·         Lower cycle than NiCad batteries

·         Thermal runaway can occur with incorrect charging or improper thermal management

·         More sensitive to temperatures than conventional lead-acid batteries

According to BatteryUniversity.com, “heat reduces the life of VRLA. Most batteries are enclosed in spaces without proper ventilation or cooling. Every 8°C (15°F) rise in temperature cuts the battery life in half. A VRLA battery, which would last for 10 years at 25°C (77°F), will only be good for 5 years if operated at 33°C (95°F). Once damaged by heat, no remedy exists to improve capacity.”

Simple Guidelines 

·         Always store in a charged condition. Never allow the open cell voltage to drop below 2.10V. Apply a topping charge every six months or when recommended.

·         Avoid repeated deep discharges. Charge more often.

·         Prevent sulfation and grid corrosion by choosing the correct charge and float voltages. If possible, allow a fully saturated charge of 14h.

·         To reverse sulfation, raise the charge voltage above 2.4V per cell for a few hours.

·         Avoid operating lead-acid at elevated ambient temperatures.

VRLA Uses:

·         Fork Lifts

·         Uninterruptible Power Supplies

·         Emergency Lighting

·         Wheelchairs

·         Telecom Back-Up Power Supplies

·         Lawn and Garden Tools

·         Engine Starters