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Texas Instruments Using the BQ35100 with Li-Primary Based Applications Application notes
Using the bq35100 with Li-Primary Based Applications
0.1
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Why bq35100 ?
The BQ35100 is an accurate low power battery
gauge that extends the life of primary batteries
through accurate gauging. The gauge offers
support for Lithium Thionyl Chloride chemistries
with an EOS(end of service) algorithm which
only consumes 0.35 uA of current as well as
support for Lithium Manganese Dioxide
chemistries with an SOH(state of health)
algorithm which only consumes .06 uA of
current. The device itself only needs to be
powered long enough to record voltage, current,
and temperature measurements used for
computing parameters in SOH and EOS mode.
These parameters, for instance, state of health
and or impedance can be recorded based on
user defined triggering of the GE pin which
controls the devices power state. The user can
obtain the results of EOS and SOH algorithms
via an I2C bus, or use the ALERT output on the
gauge as an interrupt to the host system.
Additionally, the gauge algorithms support
seamless replacement of old batteries and use
an SHA-1 authentication to help prevent
counterfeit battery usage. This gauge is best
suited for use in products such as smoke
alarms, flow meters, door access controllers,
and similar devices for early fault detection and
to maximize runtime.
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0.5
bqStudio Setup
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0.6
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Hardware
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0.3
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0.8
bqStudio Software (Program to interface
with IC)
EV2400 Firmware (Firmware for the 2400
must be updated in order to be used)
If your board does not come loaded with
firmware or you wish to change it. Navigate
to the Programming tab at the top.
Select your .srec file and press PROGRAM.
Once programming has finished press
Execute FW. See "Programming" image in
the Graphics section for reference.
Starting bqStudio
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Software
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0.4
EV2400 (Used for communicating over I2C
with the BQ35100 IC)
Power Supply (This can be a battery or
power supply, the board is powered from
this)
USB 2.0 Type A to Type B (Connect
EV2400 to your PC) I2C data cable
(Connect EV2400 to board)
Place Jumpers across ALERT/PULL-UP
Place Jumpers across GE/PULL-UP
(Toggling this turns the device on and off)
For one cell place jumpers across bottom
two “1s”.
For multi-cell you will need to place jumpers
on the top two 2-4s pins on J2.
Following this place pins on J3 indicating the
number of cells you have.
Connect your battery across BAT+ and BATConnect data cable on J1 to the I2C port on
your EV2400.
Loading Board Firmware (Optional)
•
0.2
Navigate to
http://www.ti.com/tool/BQSTUDIO and install
the software.
Board Setup
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0.7
on the board.
Connect your EV2400 to your PC and
navigate to http://www.ti.com/tool/EV2400 .
Download the firmware and execute it in
order to update your EV2400.
•
Turn on your power supply and make sure
you have jumped the GE pin.
Upon launching bqStudio the software
should auto detect the IC you are using. See
"Start Screen" in the Graphics section for
reference.
You can use the SCAN button to
continuously sample the visible parameters
or use REFRESH at your discretion.
EV2400 Setup
•
Connect usb from EV2400 to computer and
connect data cable from EV2400 to I2C port
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0.9
Using bqStudio
3. Navigate to the Data Memory tab.
1. Press UNSEAL in the Commands tab. Check
SEC1 and SEC0 in the Bit Registers window to
see that SEC1 is green and SEC0 is red. (10)
which means that the device has been
unsealed
4. In the Data Memory tab press on the
Configuration button.
5. From here press on “Operation Config A”.
6. Observe the values of Bit1 (GMSEL1) and
Bit0(GMSEL0). To be in SOH mode we need
the values to be as such GMSEL1 = 0 =green
and GMSEL0 = 1 = red. Press on GMSEL0 so
that it turns red and changes what mode we are
in and save. Reference the "GM Select" image
in the Graphics section for where you should be
when changing GM Sel.(NOTE: In the
referenced image the operating mode is set to
EOS)
2. Press RESET in the Commands tab.
3. Press CAL_TOGGLE in the Commands tab.
4. If you are using a pack with more than one
cell in series, navigate to the gas gauging tab
within the Data Memory tab. Make sure to enter
your series cell count and write it the data flash
prior to calibration. See "Series Cell Count" in
the Graphics section for reference.
7. We are now in SOH mode.
5. Navigate to the calibration tab at the top.
8. Navigate to Gas Gauging in the sidebar.
Here are variables the user can modify as
needed. Here you can enter the series cell
count, etc.
6. Check the “calibrate voltage” box and enter
the measured voltage. You may get an error
related to scanning in which navigate back to
the Registers tab and turn scanning off. Once
voltage calibration is finished uncheck the box
next to it.
7. Repeat this procedure for the current and the
temperature.
8. Finally, check Calibrate CC Offset and
calibrate.
9. Once you SOH decrease it will not increase
so you will need to press NEW_BATTERY each
time you wish to use a new cell.
0.11.1
SOH mode takes in the battery voltage and
temperature. The gauge uses these two values
and references them to the OCV lookup table in
order to determine the SOH. One important
variable to adjust in the Gas Gauging sidebar is
the” Sate of Health Max Delta”. This variable
determines by how much you SOH can change
with every cycle of the GE pin. If you plan on
sampling very frequently and reading the
voltage lower values will work. However, if your
delta value is low and the voltage drops very
suddenly you will not observe a change
immediately but rather it will take multiple cycles
to catch up to the new voltage.
9. In the Command tab press CAL_TOGGLE so
that CalMode in the Bit Registers is Green
indicating 0 which is off.
0.10 Cell Chemistry
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Navigate to the Chemistry tab.
When selecting the Chem ID, primary cell
IDs are listed as 6xxx. If you cannot find
your specific model contact Texas
Instruments on model generation.
Select the chemistry you are using and
press Program selected chemistry. See "Cell
Chemistry" in the Graphics section for
reference.
0.11 Entering Into SOH Mode
This mode is used for tracking capacity of
batteries where the capacity decreases steadily
with no sharp increases in internal impedance.
Moreover this is characteristic of Lithium
Manganese Dioxide chemistries.
1. Press UNSEAL in the COMMAND tab. Check
SEC1 and SEC0
SOH Mode Fundamentals
0.11.2
Using SOH Mode
Once you have followed the above steps, using
SOH mode is simple. Have your battery
connected to the gauge and simply cycle the
GE pin in order to get updated values of SOH
after you have finished loading and the battery’s
open circuit voltage has relaxed back up. It is
essential to wait for the battery’s open circuit
voltage to relax up in order to get accurate SOH
readings. Make sure to press NEW_BATTERY
if you are inserting a new cell.
2. Press NEW_BATTERY in the Commands
tab.
2
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0.12 Entering Into EOS Mode
and long trend averages for EOS detection.
Adjust this value in accordance with how many
times you will cycle your device. Modify the
trent detection value based on how sharp of a
decline your battery exhibits during EOS.
Additionally make sure to adjust your cell
terminate value under the Gas Gauging tab.
Values for the impedance and SOH become
available after the G_DONE bit is set to 1.
Reference the "EOS Usage" diagram in the
Graphics section for a flowchart on using the
mode as well as the "EOS Parameters" image
in the Graphics section for modifiable
parameters.
EOS is used for devices where the overall
capacity doesn’t decrease steadily with time but
rather drops off sharply at the end of its life due
to a sharp increase in impedance. Moreover
this is characteristic of Lithium Thionyl Chloride
chemistries. Reference the "Battery Impedance
at EOS" graph on the Graphics page to see a
characteristic curve of impedance increasing at
EOS.
1. Press UNSEAL in the COMMAND tab. Check
SEC1 and SEC0
2. Press NEW_BATTERY in the Commands
tab.
3. Navigate to the Data Memory tab.
0.13 When is my battery empty?
When using EOS or SOH mode it is important
to understand when a battery is dead. In
general, a battery is considered dead when the
relaxed open circuit voltage is at or below the
terminate voltage. In SOH mode the decline
towards this voltage is easy to see with each
successive discharge bringing the relaxed
voltage closer to the terminate voltage. Towards
the end of a batteries life in SOH mode, the
voltage will begin to dip to or below the
terminate voltage and relax up to subsequently
lower values with successive discharges. With
EOS mode, the sharp increase in impedance
signals that the battery is close to being
unusable and the battery is said to be
completely depleted when the voltage drops
below the terminate voltage. This change
happens rapidly and the battery itself becomes
unusable very quickly.
4. In the Data Memory tab press on the
Configuration button.
5. From here press on “Operation Config A”.
6. Observe the values of Bit1 (GMSEL1) and
Bit0(GMSEL0). To be in EOS mode we need
the values to be as such GMSEL1 = 1=red and
GMSEL0 = 0 = green. Press on GMSEL1 so
that it turns red and changes what mode we are
in and save.
7. We are now in EOS mode.
8. Navigate to the EOSData tab, here there are
important variables the user can modify which
will be subsequently discussed.
0.12.1
EOS Mode Fundamentals
EOS mode works by tracking the internal
impedance of your battery with a short trend
and long trend average. The gauge looks for a
sharp increase in the short trend average when
compared to the long trend average. The EOS
Trent Detection average is the % increase of
the short trend average in relation to the long
trend average. Once the equation below is
satisfied an EOS condition is set in the Battery
Alert register. Reference the "EOS Usage"
diagram on the Graphics page for a flowchart
on using the mode.
Short Trend Average > Long Trend Average *
(1 + EOS Trent Detection/ 100)
0.12.2
Using EOS Mode
1
Golden Image
Once you have calibrated, loaded the
chemistry, and made sure your gauge is
operating as you would like. You can extract a
"golden image" file which is essentially an
image of the flash memory that you can load
into additional gauges so that you do not have
to perform setup steps repeatedly. The
"xxx.srec" file you extract can be used to
program gauges as described in the "Loading
Board Firmware Section". In order to extract the
"xxx.srec" simply press "Create Image Files".
See the 'Golden Image" image in the Graphics
section for further reference.
One important parameter to consider is the
EOS Detection Pulse Count Thrshd. This
threshold is the number of Gauge_Start and
Gauge_Stop cycles you must perform before
your device will begin calculating the short trend
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Advanced Programming
1.1
www.ti.com
Trademarks
All trademarks are the property of their respective owners.
2
Advanced Programming
In the advanced programming tab you can send I2C commands to the gauge to read and write data. See
the "Advanced Communications" image in the Graphics section for an example of requesting the voltage.
3
Related Documentation
For information regarding sending I2C commands to your device see the Using I2C Communications
Manual .
For more detailed information about the BQ35100 see the Technical Reference Manual.
For more information about the EV2400 see the EV2400 EVM Interface Board manual.
3.1
Trademarks
All other trademarks are the property of their respective owners.
4
Using the bq35100 with Li-Primary Based Applications
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Graphics
1
Programming
Figure 1. Programming xxx.srec file
2
Start Screen
Figure 2. Start Screen
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Graphics
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5
Series Cell Count
3
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Series Cell Count
Figure 3. Modifying series cell count in data flash
6
Graphics
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Calibration
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4
Calibration
Figure 4. Calibration Screen
5
Cell Chemistry
Figure 5. Chemistry Programming Screen
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Graphics
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7
GM Select
6
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GM Select
Figure 6. GM select is toggled to change operating modes in this image the operating mode is set to EOS
7
SOH Usage
Figure 7. SOH Mode Usage Diagram
8
Graphics
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EOS Parameters
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8
EOS Parameters
Figure 8. EOS parameters that can be modified
9
EOS Usage
Figure 9. EOS Mode Usage Diagram
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Graphics
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9
Battery Impedance at EOS
10
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Battery Impedance at EOS
Figure 10. Scaled-R increasing at EOS
11
Golden Image
Figure 11. Golden image extraction
10
Graphics
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Advanced Communications
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12
Advanced Communications
Figure 12. Reading the register 0x08 which is voltage
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Graphics
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11
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