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Most ‘smart’ battery applications today are limited
to portable electronic equipment, and the electronic circuit
is built right into the battery pack. In applications where
larger ‘smart’ batteries are needed, such as electric wheelchairs,
scooters, robots and forklifts, the electronic circuit may
be placed in a box external to the battery.
The main benefit of adding intelligence to the
battery is to enable the measurement of SoH and reserve energy.
Most measuring devices used are based on voltage, which is
known to be highly inaccurate.
Cadex is extending the ‘smart’ battery technology
to wheeled applications. Called the Cadex Fuelcheck™,
the device is based on the tri-state fuel gauge described
earlier in this section. The system consists of a controller,
current measuring device and a display unit. The Cadex Fuelcheck™
device can be added to new equipment when it is manufactured
and can be installed in existing equipment as a retrofit.
The installation is permanent and each wheeled appliance requires
one system.
A tri-state linear bar graph consisting of colored
LED’s would be the preferred display for a personal user,
such as a wheelchair operator. By replacing the light display
with a digital readout, additional information can be shown.
For example, a display could indicate the remaining runtime
based on the average power consumption logged. Corrections
would be applied if the load factor changes during the course
of the day. Figure 7‑7 illustrates a digital fuel
gauge using the LCD panel.
To initialize the Cadex Fuelcheck™ system,
a one-time setup procedure is required. A PC will prompt the
technician to enter information such as battery chemistry,
desired end-of-discharge voltage, Ah rating of the battery,
and designated service flags. The system is then calibrated
by applying a full charge, followed by a full discharge. The
initial discharge assesses the battery, or learns the performance.
The SoH readings will be known after the first full discharge.
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7-7: Cadex Fuelcheck™ digital fuel gauge.
The display indicates SoC,
SoH, remaining power in hours, the voltage and
current draw.
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The simplest way to discharge the battery as
part of calibration is to run it down through normal use in
the equipment. The most accurate readings are obtained by
using a load bank. Such a device may not be always available.
With a data logging option built into the system,
the PC allows downloading service data that have been collected
during use. Such information would benefit large equipment
fleets and rental places that need to check the performance
of the batteries on demand.
Similar to other ‘smart’ battery systems, calibration
will be needed once every 6 to 12 months. More
frequent calibrations may be required if the equipment is
used for short durations between each recharge. The most practical
way to calibrate the system is by occasionally allowing the
battery to run down through continued use. Information relating
to the date of the last calibration, or an early call for
calibration if certain conditions occur, can be calculated
and displayed.
Knowing the SoH of a battery at any time and scheduling timely
service or replacement is a major benefit for industrial battery
users. Such a system would be especially helpful for organizations
in which different individuals use the equipment and no one
is given maintenance responsibilities. Equipment rental places
fall into this category.
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