BQ78PL114S12 Hardware Short Circuit Detection doesn't trigger

Gregor Rudorfer

Other Parts Discussed in Thread: BQWIZARD, BQ78PL114

I am using a BQ78PL114S12 (FW 5000) and a 4S2P Li- Ion battery pack with 4400mAh. I'm still configuring the device. Today I wanted to configure the Hardware Short Circuit Protection. I thought, this would be done quickly, but I was wrong. Although I think, I've set the values for the Hardware Short Circuit Protection, properly it never gets triggered (HSC Flag not set). Instead the 10A slow blow fuse evaporates. For testing I use a 0.68Ohm 17W resistor, because I don't want to directly short out the battery. When "shorted out" via this resistor, the pack delivers nearly 24A. This current develops a voltage drop of approx. 240mV across the 10mOhm sense resistor. This current is properly displayed in bqWizard. Sure it clips at -20A because of the 10mOhm Sense- Resistor and a gain of 5.

The Hardware Short Circuit registers are configured as follows:

Hardware Short Circuit threshold: 47

that means it should trip minimum at 12.6A and maximum at 16.8A if I'm not wrong?

Hardware Short Circuit recovery: 15

Hardware Short Circuit Time: 3

HSC Max Attempts: 1

So If I short out the battery pack via the 0.68Ohm load resistor, all other overcurrent discarge flags are set (Tier1 Tier2 ) but the HSC isn't triggered.

I don't understand where the problem is. Maybe the hardware shortcircuit detection is dependend from any other registers, although there is nothing written about it in the technical reference manual.

Please help!

Kind regards

Gregor

over 12 years ago

0 ThomasCosby over 12 years ago

TI__Guru 73830 points

Gregor,

Are you really using a 680 mohm sense resistor? I am not sure that the device can be configured to work with a sense resistor that large. The thresholds were designed to work with resistors in the 1 to 10 mohm sense resistors.Can you lower the value?

Regards

Tom

0 Gregor Rudorfer over 12 years ago in reply to ThomasCosby

Prodigy 30 points

Oh you've misunderstood me. I am using a 10mOhm sense resistor. I use a 0.68Ohm resistor as a load resistor to simulate a short circuit, without exceeding the battery's discharge current limit which is 25A. In my application I will have max. 6A current continiously flowing. So 12.6A to 16.8A is a good threshold value for short circuit detection in this case.

Here are my configurations for safety level 1

The whole configuration can be seen here

Fullscreen 3364.test1.txt Download

[System Parameters]
<SBData Dynamic>
Pack Voltage;15410;mV
Current;0;mA
Average Current;0;mA
Temperature;16,7;�C
Absolute State of Charge;29;%
Relative State of Charge;57;%
Full Charge Capacity;2239;mAh/10mWh
Remaining Capacity;1277;mAh/10mWh
Run Time To Empty;65535;Minutes
Average Time To Empty;65535;Minutes
Average Time To Full;65535;Minutes
Battery Status;0x4880
Cycle Count;0;Cycles
At Rate Time To Full;65535;Minutes
At Rate Time To Empty;0;Minutes
At Rate Ok;65535
Max Error;10;%

<SBData Static>
Manufacturer Access;0x55AA
Manufacturer Name;TEXAS;INSTRUMENTS
Device Name;bq78PL114
Device Chemistry;LION
Manufacturer Data;0E4D616E20446174612020202020200000000000000000000000000000000000
Serial Number;1
Manufacture Date;03/20/2009
Specification Info;49
Design Voltage;16800;mV
Design Capacity;4400;mAh/10mWh
Charging Voltage;0;mV
Charging Current;0;mA
At Rate;0;mAh/10mWh
Battery Mode;0x6001
Remaining Time Alarm;10;Minutes
Remaining Capacity Alarm;0;mAh/10mWh

<Pack Dynamic>
Board Temperature;16,7;�C
Pack Passed Current;-322;mAh
Cycle Since Learn;0
Epoch Hour;0
Temperature Voltage Trim;1,000
FET Status;0x0080
Safety Alert;0x2800
Safety Status;0x0800
Safety Alert1;0x0000
Safety Status1;0x0000
Permanent Disable Alert;0x8800
Permanent Disable Status;0x8800
Charge Alert;0x0000
Charge Status;0x0000
Number of Rebuilds;0
Number of Polls;1394
Number of Poll Errors;0

<Charge Control>
Pre-Charge Temperature;0,0;�C
Pre-Charge Voltage;3000;mV
Pre-Charge Recovery;3100;mV
Pre-Charge Current;240;mA
Charge Inhibit Temperature Low;0,0;�C
Charge Inhibit Temperature High;45,0;�C
Charge Inhibit  Recovery Temperature Low;5,0;�C
Charge Inhibit Recovery Temperature High;40,0;�C
Charge Suspend Temperature Low;5,0;�C
Charge Suspend Recovery Temperature Low;10,0;�C
Charge Suspend Temperature High;60,0;�C
Charge Suspend Recovery Temperature High;55,0;�C
Charge Completion Pack Voltage Qualifier;16800;mV
Charge Completion Taper Current Qualifier;275;mA
Charge Completion Time;20;Seconds;RDTE
Charge Completion FET Activation Time;10;Seconds;RDTE
Discharge Completion Pack Voltage Qualifier;12000;mV
Discharge Completion Time;4;Seconds;RDTE
Discharge Completion FET Activation Time;6;Seconds;RDTE
Discharge Under Temperature;-10,0;�C
Discharge Under Temperature Recovery;0,0;�C
Discharge Under Temperature Time;2;Seconds;RDTE
FC Set SOC Threshold;5;%
FC Clear SOC Threshold;1;%
FD Set SOC Threshold;5;%
FD Clear SOC Threshold;1;%
FD Set Voltage;12400;mV
FD Clear Voltage;12800;mV
FD Set Voltage Time;0;Seconds
Transition to Idle Current;50;mA
Transition to Idle Time;30;Seconds
Transition to Discharge Current;-75;mA
Transition to Charge Current;75;mA
Cell Shutdown Voltage;2500;mV
Design Capacity mAh;4400;mAHrs
Design Capacity 10mWh;69120;mWh
TDA Set SOC Threshold;-1;%
TDA Set Voltage Threshold;12800;mV
TDA Set Voltage Time;0;Seconds
TDA Clear SOC Threshold;-1;%
TDA Clear Voltage;14800;mV
TCA Set SOC Threshold;-1;%
TCA Clear SOC Threshold;-1;%
OCA Set Voltage;17400;mV
OCA Activation Time;2;Seconds;RDTE

<Pack History>
Lifetime Minimum Pack Voltage;15406;mV
Lifetime Maximum Pack Voltage;15413;mV
Lifetime Minimum Cell Voltage;3850;mV
Lifetime Maximum Cell Voltage;3855;mV
Lifetime Maximum Charge Current;73;mA
Lifetime Maximum Discharge Current;-15813;mA
Lifetime Delivered Amp Hours;0;Ah
Last Discharge Average;-480;mA
Lifetime Minimum Temperature;16,7;�C
Lifetime Maximum Temperature;17,4;�C
Lifetime Maximum Power;0;Watts

<Cell Balancing>
Cell 1 Net Pump;0;Pumps
Cell 2 Net Pump;0;Pumps
Cell 3 Net Pump;0;Pumps
Cell 4 Net Pump;0;Pumps
Cell 5 Net Pump;0;Pumps
Cell 6 Net Pump;0;Pumps
Cell 7 Net Pump;0;Pumps
Cell 8 Net Pump;0;Pumps
Cell 9 Net Pump;0;Pumps
Cell 10 Net Pump;0;Pumps
Cell 11 Net Pump;0;Pumps
Cell 12 Net Pump;0;Pumps
Minimum Cell Differential For Balancing;10;mV

<Cell Chemistry>
Chemistry ID;101
Aux Chemistry Version;0
Tau10;225
Normalized Dynamic Impedance Low Temperature;20,0;�C
Normalized Dynamic Impedance High Temperature;40,0;�C
Normalized Dynamic Impedance SOC;15;%
Normalized Dynamic Impedance Gain;32
FCC Learn Qualifier;5;%
Cycle Fade;0,05;%
Min OCV Slope;2;mV/%;RSOC
OCV Idle Qualifier;30;Minutes
Stale FCC Timeout;2880;Minutes
Default Charging Voltage;16800;mV
Default Charging Current;2500;mA
Capacity Algorithm;0x0003
User Rate;1000;mA
Current Delta;100;mA

<Pack Configuration>
Hardware Configuration;0x0731
Algorithm Enable;0x000E
System Control;0x0000
Parallel Count;2
Expected Number of Cells;4
Actual Number of Cells;4
Max Number of Cells;12
Temperature Sensor Count;1
Max Number of Temperatures;13
Sense Resistor;10000;uOhms
EPD Refresh Period;10;Minutes
EPD Pump Time;120;Cycle;Counts
EPD Write Time;70;Cycle;Counts
Display Driver Frequency;30;Hz
FW Build;12
Firmware Version;5000
Access Level;2

<Safety Level 1>
COV Threshold;4250;mV
COV Recovery;4100;mV
COV High Temperature Threshold;4250;mV
COV High Temperature Adjust;50,0;�C
COV Time;2;Seconds
CUV Threshold;2700;mV
CUV Recovery;3000;mV
CUV Time;1;Seconds
POV Threshold;17000;mV
POV Recovery;16400;mV
POV Time;6;Seconds
PUV Threshold;11200;mV
PUV Recovery;12000;mV
PUV Time;1;Seconds
EUV Threshold;2500;mV
EUV Time;2;Seconds
EUV Recovery;2900;mV
OC Charge Tier 1 Threshold;4800;mA
OC Charge Tier 1 Recovery;2;Seconds
OC Charge Tier 1 Time;6;Seconds
OC Discharge Tier 1 Threshold;-7200;mA
OC Discharge Tier 1 Recovery;2;Seconds
OC Discharge Tier 1 Time;8;Seconds
OC Charge Tier 2 Threshold;5200;mA
OC Charge Tier 2 Recovery;8;Seconds
OC Charge Tier 2 Time;2;Seconds
OC Discharge Tier 2 Threshold;-9600;mA
OC Discharge Tier 2 Recovery;8;Seconds
OC Discharge Tier 2 Time;1;Seconds
OC Max Attempts;3
Hardware OC Charge Threshold;211
Hardware OC Charge Recovery;1;Seconds
Hardware OC Charge Time;60
Hardware OC Discharge Threshold;39
Hardware OC Discharge Recovery;100;Seconds
Hardware OC Discharge Time;20
HOC Max Attempts;3
Hardware Short Circuit Threshold;37
Hardware Short Circuit Recovery;15;Seconds
Hardware Short Circuit Time;3
HSC Max Attempts;1
OT Charge Threshold;50,0;�C
OT Charge Recovery;45,0;�C
OT Charge Time;2;Seconds;RDTE
OT Discharge Threshold;60,0;�C
OT Discharge Recovery;50,0;�C
OT Discharge Time;2;Seconds;RDTE
Board Over Temperature;85,0;�C
Board Over Temperature Recovery;65,0;�C
Board Over Temperature Time;2;Seconds;RDTE
Hardware LP Discharge Threshold;32
Hardware LP Discharge Duration;127
Hardware LP Charge Threshold;224
Hardware LP Charge Duration;127
Host Watchdog Timeout;0;Seconds;RDTE

<Safety Level 2>
SOV Threshold;4350;mV
SOV Time;8;Seconds;RDTE
Cell Imbalance Current;50;mA
Cell Imbalance Fail Voltage;500;mV
Cell Imbalance Time;180;Seconds
Cell Imbalance SOC Inhibit Threshold;30;%
SOC Charge Threshold;6000;mA
SOC Charge Time;2;Seconds;RDTE
SOC Discharge Threshold;-12000;mA
SOC Discharge Time;2;Seconds;RDTE
SOT Charge Threshold;70,0;�C
SOT Charge Time;2;Seconds;RDTE
SOT Discharge Threshold;70,0;�C
SOT Discharge Time;2;Seconds;RDTE
Open Temperature Sensor Threshold;-40,0;�C
Open Temperature Sensor Time;2;Seconds;RDTE
FET Fail Time;2;Seconds;RDTE
Fuse Fail Limit;40;mA
Fuse Fail Time;2;Seconds;RDTE
VLAN Fail Time;2;Seconds;RDTE
Current Measurement Fail Time;10;Seconds;RDTE
Pre-Charge Voltage Timeout;900;Seconds;RDTE
Charge Duration Timeout;14400;Seconds;RDTE
IGR Limit;200
IGR Fail Count;255
IGR Ratio Limit;120
IGR Ratio Fail Count;255
Rate Limit Threshold;200
Rate Limit Activation Count;100

<Passwords>
Level 1;
Level 2;

<Calibration>
Current Gain;26426;
Coulomb Gain;26328;

[Cell Parameters]
[Cell 1]

<Dynamic>
Cell Voltage;3851;mV
Cell Temperature;16,7;�C
Temperature Rise;-0,1;�C/Min
Net Pumping;0
Est. OCV;3851;mV
Cell Status;0x0000

<History>
Cell SOC;57
OCV SOC;89;%
Stale FCC Estimate;16;Minutes
Passed mAh;-44;mAh
SOC Snapshot;89;%

<Learned>
HF Impedance;27;mOhms
Default Normalized Dynamic Impedance;60;mOhms
Normalized Dynamic Impedance;60;mOhms
QMax;2287;mAh
QRemaining;1305;mAh
Rzero;99;mOhms
Unused;0
Ra0;276;mOhms
Ra1;280;mOhms
Ra2;284;mOhms
Ra3;284;mOhms
Ra4;300;mOhms
Ra5;326;mOhms
Ra6;354;mOhms
Ra7;414;mOhms
Ra8;448;mOhms
Ra9;492;mOhms
Ra10;584;mOhms
Ra11;856;mOhms
Ra12;1104;mOhms
Ra13;1550;mOhms
Ra14;2104;mOhms

[Cell 2]

<Dynamic>
Cell Voltage;3852;mV
Cell Temperature;16,7;�C
Temperature Rise;-0,1;�C/Min
Net Pumping;0
Est. OCV;3852;mV
Cell Status;0x0000

<History>
Cell SOC;57
OCV SOC;89;%
Stale FCC Estimate;16;Minutes
Passed mAh;-44;mAh
SOC Snapshot;89;%

<Learned>
HF Impedance;26;mOhms
Default Normalized Dynamic Impedance;60;mOhms
Normalized Dynamic Impedance;60;mOhms
QMax;2342;mAh
QRemaining;1337;mAh
Rzero;0;mOhms
Unused;0
Ra0;276;mOhms
Ra1;280;mOhms
Ra2;284;mOhms
Ra3;284;mOhms
Ra4;300;mOhms
Ra5;326;mOhms
Ra6;354;mOhms
Ra7;414;mOhms
Ra8;448;mOhms
Ra9;492;mOhms
Ra10;584;mOhms
Ra11;856;mOhms
Ra12;1104;mOhms
Ra13;1550;mOhms
Ra14;2104;mOhms

[Cell 3]

<Dynamic>
Cell Voltage;3854;mV
Cell Temperature;16,7;�C
Temperature Rise;-0,1;�C/Min
Net Pumping;0
Est. OCV;3854;mV
Cell Status;0x0000

<History>
Cell SOC;58
OCV SOC;89;%
Stale FCC Estimate;16;Minutes
Passed mAh;-44;mAh
SOC Snapshot;89;%

<Learned>
HF Impedance;26;mOhms
Default Normalized Dynamic Impedance;60;mOhms
Normalized Dynamic Impedance;60;mOhms
QMax;2266;mAh
QRemaining;1315;mAh
Rzero;0;mOhms
Unused;0
Ra0;276;mOhms
Ra1;280;mOhms
Ra2;284;mOhms
Ra3;284;mOhms
Ra4;300;mOhms
Ra5;326;mOhms
Ra6;354;mOhms
Ra7;414;mOhms
Ra8;448;mOhms
Ra9;492;mOhms
Ra10;584;mOhms
Ra11;856;mOhms
Ra12;1104;mOhms
Ra13;1550;mOhms
Ra14;2104;mOhms

[Cell 4]

<Dynamic>
Cell Voltage;3853;mV
Cell Temperature;16,7;�C
Temperature Rise;-0,1;�C/Min
Net Pumping;0
Est. OCV;3853;mV
Cell Status;0x0000

<History>
Cell SOC;57
OCV SOC;90;%
Stale FCC Estimate;16;Minutes
Passed mAh;-44;mAh
SOC Snapshot;90;%

<Learned>
HF Impedance;26;mOhms
Default Normalized Dynamic Impedance;60;mOhms
Normalized Dynamic Impedance;60;mOhms
QMax;2239;mAh
QRemaining;1277;mAh
Rzero;0;mOhms
Unused;0
Ra0;276;mOhms
Ra1;280;mOhms
Ra2;284;mOhms
Ra3;284;mOhms
Ra4;300;mOhms
Ra5;326;mOhms
Ra6;354;mOhms
Ra7;414;mOhms
Ra8;448;mOhms
Ra9;492;mOhms
Ra10;584;mOhms
Ra11;856;mOhms
Ra12;1104;mOhms
Ra13;1550;mOhms
Ra14;2104;mOhms

<Safety Level 1>
COV Threshold;4250;mV
COV Recovery;4100;mV
COV High Temperature Threshold;4250;mV
COV High Temperature Adjust;50,0;°C
COV Time;2;Seconds
CUV Threshold;2700;mV
CUV Recovery;3000;mV
CUV Time;1;Seconds
POV Threshold;17000;mV
POV Recovery;16400;mV
POV Time;6;Seconds
PUV Threshold;11200;mV
PUV Recovery;12000;mV
PUV Time;1;Seconds
EUV Threshold;2500;mV
EUV Time;2;Seconds
EUV Recovery;2900;mV
OC Charge Tier 1 Threshold;4800;mA
OC Charge Tier 1 Recovery;2;Seconds
OC Charge Tier 1 Time;6;Seconds
OC Discharge Tier 1 Threshold;-7200;mA
OC Discharge Tier 1 Recovery;2;Seconds
OC Discharge Tier 1 Time;8;Seconds
OC Charge Tier 2 Threshold;5200;mA
OC Charge Tier 2 Recovery;8;Seconds
OC Charge Tier 2 Time;2;Seconds
OC Discharge Tier 2 Threshold;-9600;mA
OC Discharge Tier 2 Recovery;8;Seconds
OC Discharge Tier 2 Time;1;Seconds
OC Max Attempts;3
Hardware OC Charge Threshold;211
Hardware OC Charge Recovery;1;Seconds
Hardware OC Charge Time;60
Hardware OC Discharge Threshold;39
Hardware OC Discharge Recovery;100;Seconds
Hardware OC Discharge Time;20
HOC Max Attempts;3
Hardware Short Circuit Threshold;47
Hardware Short Circuit Recovery;15;Seconds
Hardware Short Circuit Time;3
HSC Max Attempts;1
OT Charge Threshold;50,0;°C
OT Charge Recovery;45,0;°C
OT Charge Time;2;Seconds;RDTE
OT Discharge Threshold;60,0;°C
OT Discharge Recovery;50,0;°C
OT Discharge Time;2;Seconds;RDTE
Board Over Temperature;85,0;°C
Board Over Temperature Recovery;65,0;°C
Board Over Temperature Time;2;Seconds;RDTE
Hardware LP Discharge Threshold;32
Hardware LP Discharge Duration;127
Hardware LP Charge Threshold;224
Hardware LP Charge Duration;127
Host Watchdog Timeout;0;Seconds;RDTE

0 ThomasCosby over 12 years ago in reply to Gregor Rudorfer

TI__Guru 73830 points

Gregor,

Thanks for the clarification and I should have the problem more closely. I have tested HSC before and found it to work, but I did have it not work on one occasion. It turned out to be a calibration problem in that case. I did have a customer problem previously that turned out to be a layout problem. Are your other current faults occurring at the proper thresholds? You can also place a current limited voltage across the sense resistor to test HSC and other current limits. That can be easier and safer than shorting the pack.

Regards
Tom

0 Gregor Rudorfer over 12 years ago in reply to ThomasCosby

Prodigy 30 points

ThomasCosby said:
You can also place a current limited voltage across the sense resistor to test HSC and other current limits. That can be easier and safer than shorting the pack.

That's indeed easier :)

I've recalibrated the chip. The current measurement should now be better than 1% accurate.

I've verified, that all the other current faults are occuring properly. As you suggested I've connected a PSU at the sense resistor and tested the circuit at 68mV, 74mV, 100mV and 200mV voltage drop across the sense resistor, which translates to discharge currents of 6.8A, 7.4A, 10A and 20A.

At 6.8A there were no safety rules triggered.

At 7.4A the "OC Discharge Tier 1 Threshold" was exceeded and after the "OC Discharge Tier 1 Time" the OCD Flag was set and the Discharge Mosfet was switched off.

As the "OC Discharge Tier 1 Threshold" value is -7200mA this rule worked just as expected.

At 10A the "OC Discharge Tier 2 Threshold" was exceeded and after the "OC Discharge Tier 2 Time" the OCD2 Flag was set and the Discharge Mosfet was switched off. The OCD Flag switched to yellow in bqWizard.

As the "OC Discharge Tier 2 Threshold" value is -9600mA this rule worked just as expected.

At 20A the HSC detection should kick in, but instead the BQ78PL114 just behaves like at 10A and sets the OCD2 Flag.

On the attached screenshot you can see the behavior of the Chip @ 20A discharge current. Of course I get a fuse blow failure, because I directly input the sense voltage to the chip, so switching of the Mosfets has no effect on the discharge current, so the BQ78PL114 tries to blow the fuse, which fails.

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BQ78PL114S12 Hardware Short Circuit Detection doesn't trigger