Texas Instruments BQ28Z610-R2 Technical Reference Manual Download

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6.5 FullChargeCapacity (FCC), RemainingCapacity (RemCap), and RelativeStateOfCharge
(RSOC)

The Impedance Track algorithm applies QMax, impedance, temperature, voltage, and current data to predict the
runtime

FullChargeCapacity()

RemainingCapacity()

, and

RelativeStateOfCharge()

. These values are updated if

any of the following conditions are met, reflecting the battery capacity at real time:

• QMax update occurs
• Ra update occurs
• At onset of charge and discharge
• At exit of discharge
• Every 5 hours in RELAX mode
• If temperature changes more than 5°C

6.6 Impedance Track (IT) Configuration Options

The BQ28Z610-R2 provides several Impedance Track configuration options to fine-tune the gauging
performance. These configurations can be turned on or off through the corresponding flags in

Settings

Gauging Configuration

[LOCK0]

: After a discharge event, cell voltage will usually recover to a slightly higher voltage during RELAX

state. A new OCV reading during this time can result in a slightly higher state-of-charge. This flag provides an
option to keep

RemainingCapacity()

and

RelativeStateOfCharge()

jumping back during relaxation after 0% and

FD are reached during discharge.

[RSOC_HOLD]

: An IT simulation will run at the onset of discharge. If charge terminates at a low temperature

and discharge occurs at a higher temperature, the difference in temperature could cause a small rise of RSOC
for a short period of time at the beginning of discharge. This flag option prevents RSOC rises during discharge.
RSOC will be held until the calculated value falls below the actual state.

[RSOCL]

: When set will be held to 99% until charge termination is detected.

[RFACTSTEP]

: The gauge keeps track of an Ra factor of the old (old Ra)/(new Ra) during the Ra update. This

factor is used for Ra scaling. It is limited to 3 max. During an Ra update, if (old Ra)/(new Ra) > 3, the gauge can
take on two different actions based on the setting of this flag.

If the flag is set to 1 (default), the gauge allows Ra to update once using the max factor of 3, then disables
the Ra update. If this flag is set to 0, the gauge will not update Ra and also disables the Ra update. It is
recommended to keep the default setting.

[OCVFR]

: An OCV reading is taken when a dV/dt condition is met. This is not the case if charging stops within

the flat voltage region. The change of cell voltage in this region is very small; therefore, a same voltage error can
correspond to a larger DOD error. By default, this flag is set. The device will take a 48-hour wait before taking
an OCV reading if charging stops below the

FlatVoltMax

(max flat region voltage). The

FlatVoltMax

is different

with different chemistry. A short discharge will not cancel this 48-hour wait. The 48-hour wait will only be cleared
if charging stops above the

FlatVoltMax

level. Setting this flag to 0 will remove the 48-hour wait requirement,

and OCV will be taken whenever the dV/dt condition is met. Removing the 48-hour requirement can be useful
sometimes to reduce test time during evaluation.

[RSOC_CONV]

: This function is also called fast scaling. It is an option to address the convergence of RSOC to

0% at a low temperature and a very high rate of discharge. Under such conditions, it is possible to have a drop
of RSOC to 0%, especially if the termination voltage is reached at the DOD region with a higher Ra grid interval.
To account for the error caused by the high granularity of the impedance grid interval, the

[RSOC_CONV]

, when

enabled, applies a scale factor to impedance, allowing more frequent impedance data updates used for RemCap
simulation leading up to 0% RSOC.

[Fast_QMax_LRN]

and

[Fast_QMax_FLD]

: The first flag enables fast QMax during the learning cycle when

Update Status

= 06. The second flag enables fast QMax in the field when

Update Status

≥ 06.

[RSOC_CONV]