SEALED ENERGY SYSTEMS
®
10
User Manual
safe operation throughout the life cycle of the battery.
The fuel gauge determines the State-Of-Charge (SOC) by
integrating the input and output current and using impedance
tracking to accurately track the available capacity of the attached
battery. To achieve the desired fuel-gauge accuracy, high-
performance analog peripherals are used to monitor capacity
change, battery impedance, open-circuit voltage and
temperature. These factors are continually applied to account
for battery non-linearity and environmental conditions. This
approach provides the user a meaningful and repeatable
capacity measure with minimal risk of overstating run time.
Visually, the SOC can be obtained from the four on-pack LED’s
with push- button activation.
Charge control is used to provide optimal and safe charging
requests to an SMBus level II or level III charger.
The system has three modes of operation; normal, sleep and
shutdown. In normal mode, measurements, calculations,
protection decisions and data updates are made on 1 sec
intervals. Between these intervals, the electronics enters a
reduced power mode. Sleep mode is entered when the system
senses no host or charger present. While in this mode, battery
parameters continue to be monitored at regular intervals. The
system will continue in this mode until it senses host activity
(communications or current flow). Shutdown mode occurs when
the battery voltage falls below 2.3V/parallel cell group. In this
mode, parasitic current is reduced to a minimum by shutting
down the micro- controller and all associated circuitry. If this
should happen, the battery will require an initial low current
charge to bring the battery voltage back up before normal
operation will resume.
The battery pack block diagram is shown below.
