| Common reasons
for "end of battery life" fall into a limited number of
categories.
1.
Needs
recharge only/still serviceable:
A recent U.S. Battery study
has shown that up to 15% of batteries replaced are simply flat or partially
discharged. Batteries that are flat or partially discharged, and which can
be fully restored after recharging, can be re-installed in a vehicle. It
is important to test all batteries being replaced, as there may be a problem
with the vehicle's electrical system.
2. Usage related failure:
This occurs when a battery
has prematurely failed due to extreme conditions of use commonly found in
Australia's harsh climate. Such failures include:
-
Low electrolyte levels
expose the busbars and ultimately the upper portion of the plates that
can cause irreversible sulphation, and can accelerate corrosion. The low
electrolyte levels can be the result of lack of battery maintenance, or as
a result of overcharging where fluid is lost through gassing. As an additional
problem, the acid concentration in the battery from lower electrolyte levels
can cause increased corrosion of the remaining 'wet' part of plates. Batteries
with higher electrolyte volume above the plates assist in minimising these
problems, and ensuring batteries are regularly maintained when operating
in harsh conditions will also prolong battery life.
-
High under bonnet operating
temperature. Harsh Australian operating conditions, and increasing vehicle
under bonnet operating temperatures, can cause early battery failure through
a number of areas. These conditions contribute to corrosion of the positive
plate, grid growth which can result in a short circuit, and loss of plate
active material.
-
Vibration effects. This
can cause physical damage to battery components and often sudden failure
of the battery. Vibration damage can include:
- loss of active material from the plates, resulting in a loss of battery
charge and possible short circuits.
- broken or cracked grid frames, causing short circuits; usually causing
separator damage.
- perforation of the separator envelopes at the bottom where the plates sit
in the battery case. This can result in short circuits.
-
Overcharging. Where
the vehicle charging system has been operating at a higher than normal voltage,
the battery is subjected to virtually continuous charging. This can result
in faster grid corrosion, loss of plate active material, loss of electrolyte,
plate growth and eventual disintegration of the positive plate.
-
Undercharging. This
can occur when the vehicle voltage charging system is too low to fully recharge
the battery. The result is a loss of charge and irreversible sulphation of
the battery.
3.
Plate
or Grid Related
Corrosion:
-
Grid corrosion of the Positive
plates within a battery is a normal 'end of battery life' condition that
is commonly caused due to higher operating temperatures, overcharging or
loss of electrolyte fluid. Of the positive and negative plates within a battery,
it is the positive plates where the grid metal can completely oxidise and
disintegrate due to these operating conditions.
|
-
Grid corrosion continued.-
Different alloys added to the positive grid lead can have an affect on the
corrosion rate. Antimonial lead grids generally a higher corrosion resistance
than calcium lead grids, and along with higher volumes of electrolyte above
the plates, can help overcome this problem, allowing batteries to operate
more successfully in Australia's harsh conditions.
-
Soft Positive Plate Material
("mushy plates"). This is a condition usually resulting from high operating
temperatures or overcharging. Often, both conditions may have occurred.
Sulphation. This occurs
when a battery stands in a partially or fully discharged state for long periods
of time, or is continually undercharged. As a result of these conditions
the active lead material on the plates becomes lead sulphate which also hardens
the plates. Depending on the length of time the battery has been in this
condition, the sulphation may be irreversible, in addition, if the electrolyte
level in the battery is low, the exposed part of the plates will become inactive
and sulphated. Therefore batteries with higher electrolyte levels will go
a long way to reducing problems due to sulphation and assisting longer battery
life.
4.
Open Circuit:
Including
causes such as:
-
Broken cell to cell connection.
This is where there has been a complete failure of the intercell weld.
Weld quality is critical for reliable battery performance and good working
life. This problem is largely minimised by manufacturers like Century Yuasa
Batteries and other leading manufacturers, due to accredited Quality Assured
manufacturing processes.
-
A broken busbar. This
type of failure can be caused by excessive corrosion of the busbar due to
low electrolyte level in the battery. Extensive overcharging and/or elevated
operating temperatures can also lead to accelerated corrosion of the busbars
leading to breakage and an open circuit. Batteries with the capacity for
higher electrolyte levels will help to ensure a longer battery life.
5.
Short
Circuit:
Including
causes such as:
-
Plate to busbar short
circuits can result from bent plates contacting the busbar, or corroded
positive plates which have grown upwards, contacting the busbar and causing
a short circuit. This fault can be age related and can be a normal 'end-of-life'
condition. It can also be a result of overcharging, cycling or elevated operating
temperatures.
-
Plate to plate short
circuits occur when positive and negative plates make contact causing
a short circuit, resulting in battery failure. Vibration can cause the plates
to wear or pierce the separator material leading to a short circuit. Century
Yuasa Batteries utilise strong Polyethylene Envelope separators which makes
them less susceptible to this problem.
6. Worn out or 'End of Life'
conditions:
-
The normal 'end of life' condition
in a battery is when one or more cells cease functioning due to the positive
plate grid having oxidised (corroded) and finally collapsing. Operating
temperatures have a definite effect on battery life, and high temperatures
will accelerate these 'end of life' conditions.
NEXT.
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