Rainbow Electronics MAX17047 - Manual (Page 9)

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MAX17047
ModelGauge m3 Fuel Gauge
the system is boundless. The performance of classic
coulomb counters is dominated by the accuracy of such
corrections.
Classical voltage-measurement-based SOC estimation
has poor accuracy due to inadequate cell modeling, but
does not accumulate offset error over time.
The device includes an advanced VFG, which estimates
open-circuit voltage (OCV), even during current flow, and
simulates the nonlinear internal dynamics of a lithium-ion
(Li+) battery to determine the SOC with improved accu-
racy. The model considers the time effects of a battery
caused by the chemical reactions and impedance in the
battery to determine SOC based on table lookup. This
SOC estimation does not accumulate offset error over
time.
The ModelGauge m3 algorithm combines a high-accu-
racy coulomb counter with a VFG. The complementary combined result eliminates the weaknesses of both the
coulomb counter and the VFG, while providing the
strengths of both. A mixing algorithm combines the VFG
capacity with the coulomb counter and weighs each
result so that both are used optimally to determine the
battery state. In this way, the VFG capacity result is used
to continuously make small adjustments to the battery
state, canceling the coulomb-counter drift.
The ModelGauge m3 algorithm uses this battery state
information and accounts for temperature, battery cur-
rent, age, and application parameters to determine the
remaining capacity available to the system.
The ModelGauge m3 algorithm continually adapts to the
cell and application through independent learning rou-
tines. As the cell ages, its change in capacity is monitored
and updated and the VFG dynamics adapt based on cell-
voltage behavior in the application.
Figure 2. ModelGauge m3 Overview
EMPTY
DETECTION
CURRENT
TIME RELAXED
CELL
DETECTION
CAPACITY LEARN
mAh PER %
VOLTAGE FUEL GUAGE
CURRENT
TEMPERATURE
COULOMB COUNTER
mAh OUTPUT
MIXING ALGORITHM
mAh OUTPUT
RemCap MIX
SOC MIX
APPLICATION
EMPTY
COMPENSATION
END-OF-CHARGE
DETECTION
APPLICATION
OUTPUTS:
CELL CHEMISTRY
OUTPUTS:
SOC REP
RemCap REP
SOC AV
RemCap AV
TTE
FullCAP
OCV
CYCLES
R CELL
FullCAPNom
AGE
OCV TEMPERATURE-
COMPENSATION LEARN
VOLTAGE
OCV TABLE LOOKUP
% REMAINING OUTPUT
OCV CALCULATION
OCV OUTPUT