Datasheet

bq27541-G1

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SLUSAL6C –NOVEMBER 2011–REVISED OCTOBER 2012

Avg P Last Run

The bq27541-G1 logs the power averaged from the beginning to the end of each discharge cycle. It stores this

average power from the previous discharge cycle in this register. To get a correct average power reading the

bq27541-G1 continuously multiplies instantaneous current times Voltage( ) to get power. It then logs this data to

derive the average power. This register should never need to be modified. It is only updated by the bq27541-G1

when required.

Delta Voltage

The bq27541-G1 stores the maximum difference of Voltage( ) during short load spikes and normal load, so the

Impedance Track™ algorithm can calculate remaining capacity for pulsed loads. It is not recommended to

change this value.

Ra Tables and Ra Filtering Related Parameters

These tables contain encoded data and are automatically updated during device operation. The bq27541-G1 has

a filtering process to eliminate unexpected fluctuations in Ra values while the Ra values are being updated. The

DF parameters RaFilter, RaMaxDelta, MaxResfactor and MinResfactor control the Filtering process of Ra

values. RaMaxDelta Limits the change in Ra values to an absolute magnitude. MinResFactor and

MaxResFactor parameters are cumulative filters which limit the change in Ra values to a scale on a per

discharge cycle basis. These values are Data Flash configurable. No further user changes should be made to Ra

values except for reading/writing the values from a prelearned pack (part of the process for creating golden

image files).

MaxScaleBackGrid

MaxScaleBackGrid parameter limits the resistance grid point after which back scaling will not be performed. This

variable ensures that the resistance values in the lower resistance grid points remain accurate while the battery

is at a higher DoD state.

Max DeltaV, Min DeltaV

Maximal / Minimal value allowed for delta V, which will be subtracted from simulated voltage during remaining

capacity simulation.

Qmax Max Delta %

Maximal change of Qmax during one update, as percentage of Design Capacity. If the gauges attempts to

change Qmax exceeds this limit, changed value will be capped to old value ± DesignCapacity*QmaxMaxDelta /

100.

Fast Resistance Scaling

When Fast Resistance Scaling is enabled by setting the [FConvEn] bit in Pack Configuration B, the algorithm

improves accuracy at the end of discharge. The RemainingCapacity() and StateOfCharge() should smoothly

converge to 0. The algorithm starts convergence improvements when cell voltage goes below (Terminate

Voltage + Term V Delta) or StateofCharge() goes below Fast Scale Start SOC. For most applications, the

default value of Term V Delta and Fast Scale Start SOC are recommended. Also it is recommended to keep

(Terminate Voltage + Term V Delta) below 3.6V for most battery applications.

Product Folder Links: bq27541-G1