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For users that simply need a go/no go answer
and do not want to bother about other battery information,
chargers are available that feature a target capacity selector.
Adjustable to 60, 70 or 80 percent, the target capacity
selector acts as a performance check and flags batteries that
do not meet set requirements.
If a battery falls below target, the charger
triggers the condition light. The user is prompted to press
the condition button to cycle the battery. Condition consists
of charge/discharge/charge and performs calibration and conditioning
functions. If the battery does not recover after the conditioning
service, the fail light illuminates, indicating that the battery
should be replaced. A green ready light at the completion
of the program assures that the battery meets the required
performance level.
An SMBus charger with the above described features
acts as charger, conditioner and quality control system. Figure 7‑6
illustrates a two-bay Cadex charger featuring the target capacity
selector and discharge circuit. This unit is based on Level 3
and services both SMBus and ‘dumb’ batteries.
Some SMBus chargers can be fully automated to
apply a conditioning cycle whenever the battery falls below
the target setting. An override button cancels the discharge
if a fast-charge is needed instead. Such a system maximizes
the life of fleet batteries and assures that deadwood is identified
and removed.
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Figure 7-6:The Cadex SM2+
charger
This Level 3 charger serves
as charger, conditioner and quality control system.
It reads the battery’s true state-of-health and flags
those that fall below the set target capacity. Each
bay operates independently and charges NiCd, NiMH and
Li‑ion chemistries in approximately three hours.
‘Dumb’ batteries can also be charged.
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By allowing the user to set the desired battery
performance level, the question is raised as to what level
to select. The answer is governed by the applications, reliability
standards and cost policies.
It should be noted that the batteries are always
charged to 100 percent, regardless of the target setting.
The target capacity simply refers to the amount of charge
the battery has delivered on the last discharge.
A practical target capacity setting for most
applications is 80 percent. Decreasing the threshold
to 70 percent will lower the performance standard but
pass more batteries. A direct cost saving will result. The
60 percent level may suit those users who run a low budget
operation, have ready access to replacement batteries and
can live with shorter, less predictable runtimes.
Battery SoH readings are only available with
Level 3 SMBus chargers servicing valid SMBus batteries.
‘Dumb’ batteries cannot provide SoH readings, even if they
share the identical footprint of the ‘smart’ battery and can
use the same charger.
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