T E A M
INFO:
by Isidor Buchmann Buchmann is founder and president of Cadex Electronics,
Burnaby, British Columbi | Sep 01 '96
The need to discharge nickel-cadmium (NiCd) batteries regularly to maintain
good performance has concerned users and manufacturers alike. In a desperate
attempt to find a maintenance-free battery, some manufacturers went so far
as to equip laptop computers and video cameras with the sealed lead-acid
(SLA) maintenance-free battery, which proved unsuitable because of its low
energy density. Relief was in sight in the early nineties when the nickel
metal hydride (NiMH) battery emerged and was promoted as the recommended
choice. Claimed to be maintenance-free, the NiMH is commonly used for
cellphones and notebook computers.
With twice the energy density compared to the NiCd, the new lithium-ion
(Li-ion) battery is expected to be a popular choice when it becomes readily
available. Cost has limited this chemistry to high-end applications, such as
notebook computers and specialty video cameras.
Frustrated with high operational cost, poor load characteristics and limited
cycle life of the newer battery chemistries, manufacturers are now
re-examining the old familiar NiCd, and with good reasons. When properly
maintained, the NiCd delivers an impressive 1,500 discharge-charge cycles, a
service life three times higher than that of the NiMH or Li-ion. At a cost
of only a few pennies per cycle, the NiCd is far more economical to operate
than the NiMH or Li-ion. If a NiCd battery fails to provide superior cycle
count compared to the other chemistries, lack of exercise is likely the
cause.
Battery maintenance The notion of having to apply regular discharge cycles
becomes an acceptable alternative when considering the low operational cost
of the NiCd. Because most applications do not use up all energy before
recharge, a discharge to 1V per cell (exercise) is essential for the NiCd to
prevent the buildup of crystalline formation on the cell plates. Also known
as "memory," this phenomenon eventually robs the battery of its ability to
hold charge. The capacity loss caused by memory is, to a certain extent,
reversible.
If used daily, the NiCd should be exercised once per month. The NiMH is also
affected by memory but to a lesser amount--it only needs exercise once every
three months. Because of its shorter cycle life, it is not recommended to
over-exercise the NiMH.
If no exercise is applied for several months, the crystalline formations
ingrain themselves, making it more difficult to dissolve. In such a case,
exercise is no longer effective in restoring a battery and recondition is
required. Recondition is a slow, deep discharge that drains the battery of
its remaining energy during which the crystalline structure is broken down
and the battery is commonly restored.
The importance of exercise and recondition on NiCd batteries is emphasized
by a recent study carried out by GTE Government Systems in Virginia, USA. To
determine what percentage of batteries needed replacing within the first
year of use, one group of batteries received charge only, another group was
exercised and a third group received recondition. The batteries studied were
used for portable radios on the aircraft carriers USS Eisenhower, USS George
Washington and destroyer USS Ponce.
Table 1 on page 16 shows a 45% battery failure when charge only was used. By
applying exercise, the failure was reduced to 15%. By far the best results
were achieved with recondition; the failure rate dropped to a low 5%. The
same results were obtained on all three ships.
The GTE report states further that a $2,500 battery analyzer featuring
exercise-and-recondition functions would pay for itself in less than one
month on battery savings alone. No mention was made on the benefits of
increased system reliability, an issue that is of equal or greater
importance.
Exercise and recondition are most effective when applied while the batteries
are still in reasonably good condition. Once the crystalline formation has
advanced beyond a certain stage, restoration becomes difficult, even with
recondition. If restored, a battery with advanced memory may exhibit a high
self-discharge, a deficiency that can no longer be corrected. High
self-discharge occurs when the spike-like crystalline formation punctures
the fragile separator material that insulates the negative and positive
plates. By regularly exercising the batteries, the crystalline formation is
kept under control, preventing undue damage to the separator.
Battery maintenance system Any organization using NiCd batteries on a daily
routine should set up a battery maintenance system to exercise good
batteries, rejuvenate those that fall below a set target capacity and "weed
out" the deadwood. Most companies service their batteries either when they
no longer hold charge or when the equipment is sent in for repair. As a
result, the system becomes unreliable over time, and battery-related
failures become frequent. On a routine day, a marginal battery may hold out
fine; during an emergency, however, when more energy is required, a poorly
performing battery cannot provide the extra power that is needed, and the
system subsequently fails.
Implementing a battery maintenance plan requires some effort on behalf of
management in sorting the batteries to be serviced and collecting them in
one place without disrupting the operation. Certain organizations service
the batteries in-house with their own battery analyzers, and others prefer
to send them to an independent firm specializing in that service. In both
instances, a set of spare batteries will be required to replace those that
have been removed.
If the service is done on location and the batteries can be reinstated
within 24 hours, only 10 spares in a fleet of 100 batteries are required. If
the batteries are sent away, 10 spares are needed for each day they are
away. If absent for one week, for example, 70 spares will be needed for a
fleet of 100.
After service, the batteries are marked to identify the date of service. One
simple method is to attach a color dot, each color indicating the month of
service. A different color dot is applied when the battery is reserviced the
following month. A numbering system from 1 to 12 identifying the month of
service also works well.
Many users prefer to attach a full battery label containing service date and
capacity. (See Figure 1 on page 22.) With the label method, a user requiring
a battery for a critical mission can examine the state of the battery by
simply reading the label. A battery with the highest capacity and the most
recent date will undoubtedly be chosen. Battery analyzers are now available
that automatically print a label with date, company inscription and battery
capacity when the battery is removed.
A key to successful battery maintenance is a good battery analyzer. When
first acquiring an analyzer, there is a tendency to buy on price alone. With
the requirement of servicing an ever-increasing number of different battery
types at higher volumes, second-generation buyers find the features offered
on the newer battery analyzers worth the extra cost. The benefits manifest
themselves in higher battery recovery, reduced operator time, increased
throughput, simpler operation and the use of fewer trained staff members.
One analyzer, for example, evaluates the condition of a battery and applies
a recondition cycle to restore the battery's capacity if a preset
performance level cannot be reached. User-programmable switch-mode drivers
test the batteries against preset limits, reducing the cycle time by as much
as one third compared to fixed-current units. The capacity is displayed in
percentage rather than milliampere-hours, freeing the user from memorizing
the battery ratings. Each analyzer is capable of processing four batteries
every 4-8 hours. Based on two batches per day (morning and evening
attendance) and 20 working days per month, one unit is capable of servicing
160 batteries each month. By running an extra shift and increasing the
number of working days to 30, the throughput can be doubled.
For larger throughput, Windows-based application software can be used to
network as many as 32 analyzers to a host computer. Fully extended, the
system is capable of servicing 128 batteries simultaneously.
The software collects battery test results for the database from which
inventory status, service reports and graphs are generated. Battery cups and
"smart cables" are programmable either through the analyzer's keypad, the
computer keyboard or the optional bar code reader. Custom programs and
firmware upgrades for the analyzer can be installed through the host
computer. Battery ID numbers and battery characteristics (chemistry,
voltage, rating) may be printed on bar code labels and attached to the
batteries. By reading the bar code labels, the battery to be serviced is
identified, and the battery analyzer is automatically configured to the
correct limits for the battery intended.
Conclusion The requirement for regular battery maintenance cannot be
emphasized strongly enough, both in terms of prolonging battery life and in
keeping the battery fleet in good working condition. Without any means of
measuring the performance of aging batteries, a battery fleet eventually
deteriorates to a point where it becomes completely unreliable. For NiCd
users, the battery maintenance serves two functions: a) to prevent memory
from occurring, and b) to maximize the service life of a battery.
Yawwwnnnnnnn......................ok must buy batt analyzer liao!
by Isidor Buchmann Buchmann is founder and president of Cadex Electronics,
Burnaby, British Columbi | Sep 01 '96
The need to discharge nickel-cadmium (NiCd) batteries regularly to maintain
good performance has concerned users and manufacturers alike. In a desperate
attempt to find a maintenance-free battery, some manufacturers went so far
as to equip laptop computers and video cameras with the sealed lead-acid
(SLA) maintenance-free battery, which proved unsuitable because of its low
energy density. Relief was in sight in the early nineties when the nickel
metal hydride (NiMH) battery emerged and was promoted as the recommended
choice. Claimed to be maintenance-free, the NiMH is commonly used for
cellphones and notebook computers.
With twice the energy density compared to the NiCd, the new lithium-ion
(Li-ion) battery is expected to be a popular choice when it becomes readily
available. Cost has limited this chemistry to high-end applications, such as
notebook computers and specialty video cameras.
Frustrated with high operational cost, poor load characteristics and limited
cycle life of the newer battery chemistries, manufacturers are now
re-examining the old familiar NiCd, and with good reasons. When properly
maintained, the NiCd delivers an impressive 1,500 discharge-charge cycles, a
service life three times higher than that of the NiMH or Li-ion. At a cost
of only a few pennies per cycle, the NiCd is far more economical to operate
than the NiMH or Li-ion. If a NiCd battery fails to provide superior cycle
count compared to the other chemistries, lack of exercise is likely the
cause.
Battery maintenance The notion of having to apply regular discharge cycles
becomes an acceptable alternative when considering the low operational cost
of the NiCd. Because most applications do not use up all energy before
recharge, a discharge to 1V per cell (exercise) is essential for the NiCd to
prevent the buildup of crystalline formation on the cell plates. Also known
as "memory," this phenomenon eventually robs the battery of its ability to
hold charge. The capacity loss caused by memory is, to a certain extent,
reversible.
If used daily, the NiCd should be exercised once per month. The NiMH is also
affected by memory but to a lesser amount--it only needs exercise once every
three months. Because of its shorter cycle life, it is not recommended to
over-exercise the NiMH.
If no exercise is applied for several months, the crystalline formations
ingrain themselves, making it more difficult to dissolve. In such a case,
exercise is no longer effective in restoring a battery and recondition is
required. Recondition is a slow, deep discharge that drains the battery of
its remaining energy during which the crystalline structure is broken down
and the battery is commonly restored.
The importance of exercise and recondition on NiCd batteries is emphasized
by a recent study carried out by GTE Government Systems in Virginia, USA. To
determine what percentage of batteries needed replacing within the first
year of use, one group of batteries received charge only, another group was
exercised and a third group received recondition. The batteries studied were
used for portable radios on the aircraft carriers USS Eisenhower, USS George
Washington and destroyer USS Ponce.
Table 1 on page 16 shows a 45% battery failure when charge only was used. By
applying exercise, the failure was reduced to 15%. By far the best results
were achieved with recondition; the failure rate dropped to a low 5%. The
same results were obtained on all three ships.
The GTE report states further that a $2,500 battery analyzer featuring
exercise-and-recondition functions would pay for itself in less than one
month on battery savings alone. No mention was made on the benefits of
increased system reliability, an issue that is of equal or greater
importance.
Exercise and recondition are most effective when applied while the batteries
are still in reasonably good condition. Once the crystalline formation has
advanced beyond a certain stage, restoration becomes difficult, even with
recondition. If restored, a battery with advanced memory may exhibit a high
self-discharge, a deficiency that can no longer be corrected. High
self-discharge occurs when the spike-like crystalline formation punctures
the fragile separator material that insulates the negative and positive
plates. By regularly exercising the batteries, the crystalline formation is
kept under control, preventing undue damage to the separator.
Battery maintenance system Any organization using NiCd batteries on a daily
routine should set up a battery maintenance system to exercise good
batteries, rejuvenate those that fall below a set target capacity and "weed
out" the deadwood. Most companies service their batteries either when they
no longer hold charge or when the equipment is sent in for repair. As a
result, the system becomes unreliable over time, and battery-related
failures become frequent. On a routine day, a marginal battery may hold out
fine; during an emergency, however, when more energy is required, a poorly
performing battery cannot provide the extra power that is needed, and the
system subsequently fails.
Implementing a battery maintenance plan requires some effort on behalf of
management in sorting the batteries to be serviced and collecting them in
one place without disrupting the operation. Certain organizations service
the batteries in-house with their own battery analyzers, and others prefer
to send them to an independent firm specializing in that service. In both
instances, a set of spare batteries will be required to replace those that
have been removed.
If the service is done on location and the batteries can be reinstated
within 24 hours, only 10 spares in a fleet of 100 batteries are required. If
the batteries are sent away, 10 spares are needed for each day they are
away. If absent for one week, for example, 70 spares will be needed for a
fleet of 100.
After service, the batteries are marked to identify the date of service. One
simple method is to attach a color dot, each color indicating the month of
service. A different color dot is applied when the battery is reserviced the
following month. A numbering system from 1 to 12 identifying the month of
service also works well.
Many users prefer to attach a full battery label containing service date and
capacity. (See Figure 1 on page 22.) With the label method, a user requiring
a battery for a critical mission can examine the state of the battery by
simply reading the label. A battery with the highest capacity and the most
recent date will undoubtedly be chosen. Battery analyzers are now available
that automatically print a label with date, company inscription and battery
capacity when the battery is removed.
A key to successful battery maintenance is a good battery analyzer. When
first acquiring an analyzer, there is a tendency to buy on price alone. With
the requirement of servicing an ever-increasing number of different battery
types at higher volumes, second-generation buyers find the features offered
on the newer battery analyzers worth the extra cost. The benefits manifest
themselves in higher battery recovery, reduced operator time, increased
throughput, simpler operation and the use of fewer trained staff members.
One analyzer, for example, evaluates the condition of a battery and applies
a recondition cycle to restore the battery's capacity if a preset
performance level cannot be reached. User-programmable switch-mode drivers
test the batteries against preset limits, reducing the cycle time by as much
as one third compared to fixed-current units. The capacity is displayed in
percentage rather than milliampere-hours, freeing the user from memorizing
the battery ratings. Each analyzer is capable of processing four batteries
every 4-8 hours. Based on two batches per day (morning and evening
attendance) and 20 working days per month, one unit is capable of servicing
160 batteries each month. By running an extra shift and increasing the
number of working days to 30, the throughput can be doubled.
For larger throughput, Windows-based application software can be used to
network as many as 32 analyzers to a host computer. Fully extended, the
system is capable of servicing 128 batteries simultaneously.
The software collects battery test results for the database from which
inventory status, service reports and graphs are generated. Battery cups and
"smart cables" are programmable either through the analyzer's keypad, the
computer keyboard or the optional bar code reader. Custom programs and
firmware upgrades for the analyzer can be installed through the host
computer. Battery ID numbers and battery characteristics (chemistry,
voltage, rating) may be printed on bar code labels and attached to the
batteries. By reading the bar code labels, the battery to be serviced is
identified, and the battery analyzer is automatically configured to the
correct limits for the battery intended.
Conclusion The requirement for regular battery maintenance cannot be
emphasized strongly enough, both in terms of prolonging battery life and in
keeping the battery fleet in good working condition. Without any means of
measuring the performance of aging batteries, a battery fleet eventually
deteriorates to a point where it becomes completely unreliable. For NiCd
users, the battery maintenance serves two functions: a) to prevent memory
from occurring, and b) to maximize the service life of a battery.
Yawwwnnnnnnn......................ok must buy batt analyzer liao!
(it still flies very well though)
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