AGM Explained
AGM Explained
Yuasa Automotive AGM
• Improved active mass efficiency, through better
absorption of the acid
• Increased lifespan due to minimal active material
shedding due to battery design
• Higher cold start values
• Totally Maintenance Free – zero water
• Spill proof/leak proof
• Designed to meet latest OEM vehicle demands
• Compatible with sensitive electronic equipment
• AGM technology now factory fitted to numerous
luxury cars and “Stop – Start” vehicle where
increased AGM battery features are required
Yuasa’s world leading motorcycle and industrial AGM
(absorbent glass mat) technology comes to the automotive
market. The Yuasa automotive AGM battery has been
engineered to meet the growing extreme power demands of
recently introduced vehicles now starting to enter the
European aftermarket. Yuasa’s automotive AGM experience
comes from vehicles such as the Mazda MX5 and the famous
Toyota Prius and has now been launched for European vehicle
battery designs.
The new Yuasa AGM European 096 and 019 sized batteries
provide reliable starting whilst coping with the extreme power
needs of the modern vehicle. Laboratory evaluation is boasting
4-5 times the cyclic durability of standard conventional flooded
product and typically 16% higher starting power, even at lower
temperatures. Increased reaction surface area ensures
increased energy densities for faster engine rotation during
starting and therefore maximising fuel efficiency.
The AGM batteries utilises the same absorbent glass mat
technology as used in Yuasa Motorcycle and Industrial
batteries which have been on the market for over 44 years
(1965). This absorbent glass mat absorbs the battery’s acid,
enabling a more efficient use of the cell’s volume without the
need for electrolyte reservoirs, as needed with conventional
flooded batteries. The absorbent glass mat gives a number of
key benefits to the design of the lead acid battery;Within normal operating conditions, the use of the individual
cell valve design and glass mat plate separation ensures
gas recombination occurs and ensures that no water is
lost therefore negating the need for electrolyte reservoirs
and freeing the user from maintenance.
• One way venting system providing partial pressure in
each cell ensuring 100% leak proof and safe handling.
• The increased pack pressures of the AGM battery
increase the batteries resistance to vibration.
• More reaction surface area ensuring higher starting
capacity within the same footprint as conventional
flooded batteries.
Q. What are the differences between flooded and AGM
Lead Acid batteries?
A. See above, AGM batteries are built using a glass mat
separator which enable all the electrolyte required by the
battery to be stored within the glass mat, also allowing any
gasses given off during charging to be recombined into
water meaning that the batteries are totally maintenance
free. The design benefits of the glass mat over
conventional flooded batteries enable the battery pack to
operate under higher pressure without the fear of
insufficient electrolyte between the plates, leading to the
step change in durability offered by AGM batteries over
flooded. The quality of the glass mat is a critical item in
ensuring the optimum life of the battery versus its
application. This experience has been gained by Yuasa
from over 44 years experience in the field using this
technology. The automotive application battery designs
are balanced with greater high rate starting performance
and cycle life for the increased service/technological
requirements of modern vehicle designs.
Q. What are the differences between GEL and AGM
(starved) batteries?
A. Both are recombinant batteries (i.e. under normal
operating conditions they recombine the gases given off
during charging to form water) and both are classified as
sealed valve regulated.
The major difference is that in the AGM, the electrolyte is
fully soaked into a special absorbed glass mat separator
which immobilises the acid, whereas in the GEL batteries
the acid is mixed with Silica to form a GEL also
immobilising the acid. The benefits of AGM over GEL are
that with the use of absorbed glass mat, the battery pack
can be operated under a greater operating pressure so
improving cyclic durability. With GEL, similar pack pressure
can not be used so durability is usually provided by
increased paste density which is good for life but not as
good for high rate startability performance as required for
automotive applications.
Q. Why is charging voltage so critical to both GEL and
AGM batteries?
A. Charge voltage is critical with these types of batteries as
both are recombinant batteries. This means that the
oxygen that is normally produced on the positive plate in all
lead acid batteries recombines with hydrogen given off by
the negative plate. The recombination of the hydrogen and
oxygen produces water, which recycles back to the battery
acid, therefore the battery is maintenance free and does
not need topping up.
• The acid absorption of the glass mat means that the
battery packs can be operated under higher pressures
than conventional flooded batteries this has benefits
including significantly prolonging battery cycle durability
by minimising paste shedding.
Frequently Asked questions
The sealing vent used in the design ensures that a positive
internal pressure is maintained to ensure the
recombination of the gasses occur and not allow the cell to
dry out and fail.
YUASA - The world's leading battery manufacturer
AGM Explained continued
In addition, the valve must safely release any excess
pressure that may be produced during overcharging (e.g.
alternator rectifier fault), otherwise the cell would be
irreversibly damaged. The excessive pressure that the
valve is releasing is both hydrogen and oxygen which can
not recombined within the battery so breaks the cycle, net
result is that battery would eventually dry out.
It must be noted that an AGM battery must never be
opened once it leaves the factory, as sulphation could
occur on the plates leading to an irreversible loss in
Gel batteries are more critical to correct charging as
overcharge can lead to the gel being irreversibly damaged,
AGM are not subject to this failure mode and hence are
more suitable for automotive use.
Q. Can I store my AGM battery in my garage during the
winter or will it freeze?
A. As with flooded batteries, providing the batteries are kept
in a charged state, batteries can be stored without any
fears of freezing.
Q. Can I store my AGM battery on the garage floor?
A. Many people have the impression that when batteries sit
on concrete the energy “leaks out”, the truth is that you can
let any modern battery sit on concrete without fear of harm
or accelerated self discharge.
This myth stems from the days of the old wooden/glass
case batteries, where damp floors led to water soaking up
into outer wooden cases causing swelling of the wood. In
fact with modern batteries in hard plastic cases, concrete
is generally an excellent surface on which to store a battery.
The key issue is that the floor should not have any sharp
objects which may damage the battery casing; there are
no electrochemical reasons.
Q. Do AGM batteries have a memory?
A. No, this is only a function of Nickel Alkaine Battery system
such as Nickel cadmium.
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