This document answers the frequently asked questions on VRLA (Valve Regulated Lead Acid) batteries. It will give a good overview about VRLA batteries and their advantages/disadvantages compared to the more popular FLA (Flooded Lead Acid) batteries.

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FAQS ON
VRLA BATTERIES

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FAQs on VRLA Batteries
Q. What does VRLA stand for?
A. VRLA stands for Valve Regulated Lead Acid. VRLA batteries are
maintenance free batteries and vice versa. They are one and the same.
Q. What does SMF stand for?
A. SMF stands for “Sealed Maintenance Free”. SMF batteries are maintenance
free batteries and vice versa. So maintenance free batteries, SMF batteries, and
VRLA batteries are all one and the same

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FAQs on VRLA Batteries
Q. What are maintenance free batteries called VRLA batteries?
A. VRLA batteries work on the oxygen recombination principle. However, the
recombination process is not 100% efficient. So over time, the internal pressure
increases, and some amount of gases have to be released to maintain the ideal
pressure. This is achieved with the help of one-way, pressure-sensitive valves
which open when the internal pressure increases above a certain threshold and
allow the excess gases to be vented. That is why these batteries are called VRLA
or valve regulated lead acid batteries. Excess gases are also produced if these
batteries are overcharged or discharged at rates higher than the recommended
rate.

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FAQs on VRLA Batteries
Q. What is the basic principle of operation of maintenance free batteries?
A. In flooded batteries, oxygen and hydrogen are produced when the batteries
discharge. These gases escape from the battery, which leads to loss of water. That
is why flooded batteries have to be periodically filled with distilled water.
However, in the case of maintenance free batteries, the oxygen and hydrogen
combine to form water. That is why they remain moist and don’t have to be
periodically filled with distilled water.

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FAQs on VRLA Batteries
Q. Do I have to periodically add distilled water to FLA batteries?
A. Yes, you have to periodically add distilled water to flooded batteries. The
level of the electrolytic fluid in the battery must be maintained between the min
and max levels at all times to ensure that the battery works properly and doesn’t
become dry. If the battery becomes dry, its life reduces drastically.

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FAQs on VRLA Batteries
Q. What is the oxygen recombination principle?
A. Oxygen recombination principle is the main principle of operation of
maintenance free batteries, and is what makes it possible to have maintenance
free batteries.
In flooded batteries, oxygen and hydrogen are produced when the batteries
discharge. These gases escape from the battery, which leads to loss of water. That
is why flooded batteries have to be periodically filled with distilled water.
However, in maintenance free batteries, oxygen released from the +ve plate
travels to the -ve plate where it combines with hydrogen to form water. It is
because of this recombination that maintenance free batteries remain moist and
don’t have to be periodically filled with distilled water.

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FAQs on VRLA Batteries
Q. Is the recombination efficiency 100%?
A. No, the recombination efficiency is never 100%! It is always less than 100%.
But how less is what separates the good batteries from the not so good ones.
EverExceed maintenance free batteries have a recombination efficiency of more
than 99% for most batteries, and in some batteries it is even higher than that. And
that is the main reason for their superior performance.

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FAQs on VRLA Batteries
Q. If the recombination efficiency is not 100%, what happens to the gases
that are emitted?
A. The gases that are emitted collect in the maintenance free batteries, which
leads to a rise in the internal battery pressure. When the pressure exceeds a
threshold, the one-way pressure sensitive valves open and release the gases bring
the internal battery pressure back to the ideal levels.
That is why maintenance free batteries are called “valve regulated lead acid”
batteries, or VRLA in short.

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FAQs on VRLA Batteries
Q. What are the advantages of maintenance free batteries compared to FLA
batteries?
A. The advantages of maintenance free batteries compared to FLA batteries are:
• They do not produce gases during normal operation or while charging. Therefore, they can be kept in
the vicinity of any electrical equipment or any inflammable material, unlike flooded lead acid
batteries.
• They do not emit acid spray even if charged abusively. Of course, charging abusively will have an
adverse effect on battery life.
• They are spill-proof and leak-proof.
• They can be used in vertical or horizontal position (which is something that you can’t do with
flooded lead acid batteries).
• They can be transported without any restrictions:
• Surface transport: Classified as non-hazardous material as per DOT-CFR Title 49 parts 171-189.
• Marine transport: Classified as non-hazardous material as per IMDG amendment 27.
• Air transport: Comply with IATA/ICAO, Special Provision A67.

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FAQs on VRLA Batteries
Q. What are the disadvantages of maintenance free batteries compared to
FLA batteries?
A. The advantages of maintenance free batteries compared to FLA batteries are:
• They cannot provide the kind of discharge currents that flooded batteries can
provide.
• They are more expensive than flooded batteries.
Q. What are the two basic types of VRLA batteries?
A. The two basic types of VRLA batteries are VRLA AGM and VRLA Gel.

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FAQs on VRLA Batteries
Thank you!