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SLUA777–June 2016
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Copyright © 2016, Texas Instruments Incorporated
How to Complete a Successful Learning Cycle for the bq28z610/bq78z100
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Application Report
SLUA777–June 2016
How to Complete a Successful Learning Cycle for the
bq28z610/bq78z100
Onyx Ahiakwo......................................................................................... Battery Management Solutions
ABSTRACT
The 1- to 2- series bq28z610 which uses I2C communication protocol and the bq78z100 which uses the
HDQ communication protocol are based off the same hardware platform. The Impedance track algorithm
on both devices is identical as well as most of the registers. This paper discusses the steps necessary to
complete the initial optimization cycle (also known as learning cycle) in order to ensure the accuracy and
excellent performance of the gauge.
Contents
1 Introduction ................................................................................................................... 1
2 Chem id Identification and Programming ................................................................................. 1
3 Data Flash Configuration Settings Pertinent to Learning Cycle Completion......................................... 3
4 Learning Cycle .............................................................................................................. 4
5 Learning Cycle Summary in Graphical Form ............................................................................ 6
6 Conclusion .................................................................................................................... 8
1 Introduction
Impedance track is a proprietary algorithm developed by Texas Instruments where the battery gauge
dynamically learns the resistance and the total chemical capacity of the battery. In order to go into
production using the bq28z610 / the bq78z100, a golden file has to be created which is programmed on
multiple devices. The learning cycle is a part of the golden file creation process which requires the user to
carry out a few cycles on the pack to make sure that possible variation in cell manufacturer processes is
accounted for in the learned resistance as well as to account for the board contact and trace resistances
which could impact the gauges state of charge reporting and accuracy.
2 Chem id Identification and Programming
The chem id is a look up table which the gauge uses for determination of state of charge during
initialization. The gauge also uses this table as part of the IT algorithm to predict remaining capacity. This
table consists of the open circuit voltage profile of the battery from full to empty as well as the resistance
of the battery which is spit up into grid points that corresponds to different state of charges. Both the OCV
and resistance tables have the temperature dependent components which aids gauge performance at
different temperatures. It is important that the chem id programmed on the gauge was either generated by
TI for that battery or a close match to an existing chem id in TI data base for batteries is identified using
our online chem id identification tool - gpcchem. The chem id identification requires running a relax-
discharge-relax (rel-dis-rel) test while logging data using the gauge’s GUI (bqstudio) and then using gpc
chem tool with the logged data to identify a close match. If there is no match, then the cells have to be
sent to TI for characterization and chem id generation. Contact a local field applications engineer if cells
have to be sent to TI. Once a chem id has been identified or created, it has to be programmed on the fuel
gauge. The user can select the new found chem id and program it using the chemistry plug-in of bqstudio
as shown in Figure 1.