questions re: bq2084 / bq29312a chipset

Hi Tom,

thanks for your reply.... screenshot below, let me know if this comes through ok. I'm looking for a simple solution, where fault safety measures are reset after the fault is removed.

John

OK, thanks Tom. I'm really under the gun on this one so anything you can do to help is greatly appreciated. I'll be looking forward to your reply.

John

Hi John,

Tom was covering for me while on vacation, but I'm back now. For the discharge FET during cell undervoltage recover, are you sure there isn't something else violating a safety parameter, like temperature? Did ALL the cells exceed the 2700 mV?

If you can attach your .gg file, I'll try to duplicate it here tomorrow.

Regards,

Doug

Hi Doug, in my test setup only one cell of the three went below my low voltage threshold of 2300mV, the others stayed above 2700mV. When the one cell went below 2300mV, the DCH FET turned off as expected. When i turned the voltage back up beyond 2700mV, the DCG FET did not come back on.

We're not sure what the .gg file is... can you tell us where to find that? We have the USB programming box for the bq2084 chipset, and we seem to be able to program the chipset via the windows interface, but not sure what or where the .gg file is located. Below is a screen capture of the values we programmed into the bq2084. thanks in advance for any help you can provide... time is very tight on our end...

John

Refering to your Data Flash screen, use the file menu to save the data flash constants. That will write a text file with .gg extension. If you attach it here i can test it for you.

Hi Doug,

Here is the .gg file, let me know if it came thru ok. i got a message that i couldn't post .gg files, so i changed the extension to .txt.

[Device]
Name=bq2084
[Gas Gauge Flash Constants]
Version=01.43
Remaining Time Alarm=0
Remaining Cap Alarm=0
Design Voltage=10800
Specification Info=0000
MfrDate(yyyy-mm-dd)=2003-07-01
Serial Number=2
Cycle Count=15
Manufacturer Name=AURORA     
Device Name=SPHERES
Device Chemistry=LION
Pack Configuration=06
Gauge Configuration=26
Misc Configuration=1AB8
Deadband=9860
Self Discharge Rate=0.2
Electronics Load=0
Battery Low %=5.00
Near Full=200
Design Capacity=1950
Full Charge Capacity=1950
Cycle Count Thresh=1462
Charging Voltage=12600
Pre-charge Voltage=0
Fast Charging Current=1950
Maint Charging Curr=0
Pre-charge Current=50
Pre-charge Temp=10.0
Chg Inhibit Temp Low=10.0
Chg Inhibit Temp High=50.0
Fast Charge Term=100.00
Fully Charged Clear=95
Current Taper Thresh=25
Current Taper Vltg=25
Taper Termination Min=38.0
Maximum Over Chg=200
Charge Efficiency=100.00
Overload Current=2500
Overvoltage Margin=150
Clear Fail Current=1000
Cell OV Set=4250
Cell OV Reset=4150
Cell UV Set=2300
Cell UV Reset=2700
Terminate Voltage=8475
Safety Voltage=13000
Chg Suspend Temp Hi=45.0
Chg Susp Temp Hi Rst=40.0
Over Temp Dsg=60.0
Over Temp Dsg Rst=50.0
Safety Temp Chg=65.0
Safety Temp Dsg=65.0
Chg Suspend Temp Lo=10.0
Shutdown Voltage=6900
VOC 75=11175
VOC 50=9750
VOC 25=8325
Emf (EDV0)=2300
EDV C0 (EDV1)=2550
EDV R0 (EDV2)=27000
EDV T0=4475
EDV R1=250
EDV TC=3
EDV C1=0
Learning Low Temp=12.0
AFE OC Dsg Vltg=0F
AFE OC Dsg Delay=0F
AFE SC Chg T/V=F0
AFE SC Dsg T/V=F0
AFE Vref=9786
Sense Resistor=0.0200
CC Delta=0.0000323
CC Offset=32767
DSC Offset=38
ADC Offset=38
Temperature Offset=0.0
Board Offset=0
AFE Fail Limit=2
Cell Bal Thresh=3900
Cell Bal Window=100
Cell Bal Minimum=40
Cell Bal Interval=20
Cell Imbalance Thresh=250
Cell Bal Vcell Max=4250
Cell Bal Imax=325
Cell Imbalance Time=20
AFE Check Time=0
Sleep Current Thresh=0.0
Sleep Curr Multiplier=5
Sleep Time=20
Mfr Info 1=0000
Mfr Info 2=0000
Mfr Info 3=0000
Vmax Charge Vltg=4250
Voff Charge Vltg=4250
Von Charge Vltg=4200
Pulse Max On Time=60.00
Pulse Min Off Time=0.1250
Max Charge Time=28800
Pre-charge Detection=10
Chg Detection=100
Dsg Detection=-150
PF Status=67
PF Flag=00
PF Config=00
PFIN Time=0
FET Fail Chg Curr=20
FET Fail Dsg Curr=-20
FET Fail Time=20
Chg OC Threshold=1950
Chg OC Time=6
Dsg OC Threshold=25000
Dsg OC Time=5
Fault Reset Time=5
Vpack Threshold=8000
Shutdown Timer=20
=

thanks again,

John

Yes, it came through fine John. I'll try to duplicate your issue tomorrow.

Hi John,

The CUV recovery works fine for me using your .gg file. However, I think I may have spotted your problem. You have the Shutdown Voltage set to 6900 mV, which is exactly 3 times the Cell UV setting of 2300 mV. So, it I leave 2300 mV per cell on the device for more than a couple seconds the IC shuts itself down and the display on the EVSW locks up. Could that be happening to you?

In any case we recommend that you put some distance between your CUV threshold and the Shutdown Voltage threshold.

Regards,

Doug 

Hi Doug,

We are running this on our target system without the EVSW in the loop. We have a programming connector on our target and we use the EV2300 to program the chipset initially, but then we disconnect for actual operation, i don't know what the EVSW display would be doing during my testing.

We changed the CUV to 2500, but i get the same response. At the moment, i am using 3 independent power supplies to simulate 3 batteries. When i set nominal values for my power supplies (~3V each), both FETs are ON. When i adjust 1 supply below 2500mV the DCG FET turns OFF as expected. When i adjust it back up above the threshold (currently 2700mV) and all the way back up to 3V, DCG never turns back on. If i then power cycle the supplies, DCG turns back ON. Almost as if we are resetting a reg value maybe? I'd like the DCG FET to turn back on automatically when the cell voltage rises above the reset threshold, with no need for an MPU to reset anything in SW.

Please let me know if there's an opportunity to speak more directly to speed up the debug process. I can also send you the schematic for our target system if that'll help speed things up. Thanks again for your help.

John

Hi Doug,

I'm wondering if it might be easier for me to stipulate to you what our intent is for cell and pack control (i.e. intended overvoltage, undervoltage cell balance settings etc) and maybe you can spot if we have discrepancies in our register settings? I'm having some trouble correlating the 'Name' fields in the EVSW programming interface with the actual register values in the bq2084/bq29312a chipset, and i'm worried whether something is incorrectly programmed on our end. Is there a document that best describes how to populate the 'Value' fields in the EVSW programming interface?

Some details on my system are included in the below paragraph.

This is a 3 series cell pack, the capacity of the cells is 1.95Ahr. My intent is to charge them at C/2 (~1A). My nominal discharge rate is about 0.5A, but could be as high as 1A. I would like to employ the bq2084/bq29312 cell balancing. cell overvoltage threshold should be 4.25V/cell, cell undervoltage threshold 2.5v/cell.

I can supply any further information you may need, thanks....

John

I'm also noticing when i charge batteries, that my highest cell seems to charge faster than the middle and bottom cells. it reaches cell termination quickly and disables charging when it hits the overvoltage threshold. I am attaching a schematic of the circuit... it's pretty much a cut and paste of the reference design with few modifications. The U4/Q4 network in the lower right corner is a secondary pack-level undervoltage shutoff.

Any help you can provide is greatly appreciated!

thanks,

John

Hi Doug,

Are you still evaluating my inquiry? I haven't received a response in awhile.

thanks,

John

Hi Doug,

i am attaching the latest .gg file. i am running our custom board with the bq2084/29312a chipset with the EVSW attached. I am using a power supply and a series RC network to simulate 3 series li-ion cells. At present, i have the CVOV programmed for 4.25V/cell and the CVUV programmed for 2.3V/cell. When i exceed these limits, i see the corresponding CVOV or CVUV bit set in the 'Status Bits' section of the SBS screen, however this action does not seem to turn off the corresponding CHG FET or DCG FET.

Table 10 in the bq2084 datasheet indicates the FETs should be getting shut off when these status bits are set. Any suggestions? i am hoping to wrap up this testing this week.

thanks in advance,

John

[Device]
Name=bq2084
[Gas Gauge Flash Constants]
Version=01.43
Remaining Time Alarm=10
Remaining Cap Alarm=360
Design Voltage=10800
Specification Info=0031
MfrDate(yyyy-mm-dd)=2003-07-01
Serial Number=1
Cycle Count=0
Manufacturer Name=AURORA     
Device Name=bq2084 
Device Chemistry=LION
Pack Configuration=26
Gauge Configuration=41
Misc Configuration=0BB9
Deadband=9860
Self Discharge Rate=0.2
Electronics Load=0
Battery Low %=7.03
Near Full=200
Design Capacity=1950
Full Charge Capacity=1950
Cycle Count Thresh=975
Charging Voltage=12600
Pre-charge Voltage=2000
Fast Charging Current=975
Maint Charging Curr=0
Pre-charge Current=128
Pre-charge Temp=9.6
Chg Inhibit Temp Low=0.0
Chg Inhibit Temp High=45.0
Fast Charge Term=100.00
Fully Charged Clear=95
Current Taper Thresh=78
Current Taper Vltg=225
Taper Termination Min=22.5
Maximum Over Chg=50
Charge Efficiency=100.00
Overload Current=5000
Overvoltage Margin=300
Clear Fail Current=256
Cell OV Set=4250
Cell OV Reset=4200
Cell UV Set=2300
Cell UV Reset=2500
Terminate Voltage=8475
Safety Voltage=13250
Chg Suspend Temp Hi=60.0
Chg Susp Temp Hi Rst=55.0
Over Temp Dsg=70.0
Over Temp Dsg Rst=60.0
Safety Temp Chg=75.0
Safety Temp Dsg=75.0
Chg Suspend Temp Lo=0.0
Shutdown Voltage=7500
VOC 75=11886
VOC 50=11430
VOC 25=11268
Emf (EDV0)=3000
EDV C0 (EDV1)=3250
EDV R0 (EDV2)=3400
EDV T0=0
EDV R1=0
EDV TC=0
EDV C1=0
Learning Low Temp=11.9
AFE OC Dsg Vltg=00
AFE OC Dsg Delay=0F
AFE SC Chg T/V=F0
AFE SC Dsg T/V=F0
AFE Vref=9760
Sense Resistor=0.0200
CC Delta=0.0000327
CC Offset=-11714
DSC Offset=31
ADC Offset=35
Temperature Offset=-2.8
Board Offset=0
AFE Fail Limit=2
Cell Bal Thresh=3900
Cell Bal Window=100
Cell Bal Minimum=10
Cell Bal Interval=20
Cell Imbalance Thresh=25
Cell Bal Vcell Max=4200
Cell Bal Imax=158
Cell Imbalance Time=5
AFE Check Time=0
Sleep Current Thresh=5.0
Sleep Curr Multiplier=1
Sleep Time=10
Mfr Info 1=0000
Mfr Info 2=0000
Mfr Info 3=0000
Vmax Charge Vltg=4280
Voff Charge Vltg=4280
Von Charge Vltg=4200
Pulse Max On Time=60.00
Pulse Min Off Time=0.0000
Max Charge Time=16200
Pre-charge Detection=10
Chg Detection=100
Dsg Detection=-150
PF Status=05
PF Flag=00
PF Config=00
PFIN Time=5
FET Fail Chg Curr=20
FET Fail Dsg Curr=-20
FET Fail Time=20
Chg OC Threshold=2925
Chg OC Time=6
Dsg OC Threshold=3000
Dsg OC Time=10
Fault Reset Time=30
Vpack Threshold=2000
Shutdown Timer=20
=

Hi,

I'm still trying to debug another issue with the bq2084 / bq29312a chipset. I can't seem to get the pack to shut off in discharge mode after reaching a particular pack voltage level. I'm confused whether the discharge voltage shutoff function is programmed via the "Shutdown" register, "terminate voltage" register, "EDV0" register, or some other means.

In discharge mode, the pack will shut off when any cell hits the programmed CVUV level, but i'd also like to program the pack to shut off when the overall pack voltage reaches a programmed minimum value. I can provide a .GG file for degugging.

thanks,

John

I have looked at a number of options and been through the datasheet pretty thoroughly, but can't seem to figure this out. Pack voltage falling below the 'Terminate Discharge Threshold' just seems to activate the Terminate Discharge Alarm, but does not turn off the discharge FET, nor does pack voltage falling below EDV0. The 'Shutdown' threshold seems to be reserved as a last action to preserve the batteries by shutting down all electronics, but that seems to be a last resort. There should be a way to program the bq2084 to simply turn off the discharge FET when the pack voltage hits a programmed minimum threshold. Thanks in advance for any assistance with this.

John

OK, thanks Tom. A little disappointing that CVUV is the only means to turn off the DCG FET during normal discharge. I think i had assumed there must also be a pack low-level voltage threshold that could be used to turn of DCG FET.... reserving CVUV only for off-nominal cases of extreme cell imbalance. With this in mind, i will do as you suggest and re-scale CVUV to turn DCG FET off when my pack voltage reaches my desired undervoltage threshold.

One more question (for now) re: 'Capacity Learning (FCC Update) and Qualified Discharge'. Page 11 of bq2084 datasheet lists criteria for a 'qualified discharge' (resulting in VDQ=1 during discharge). Most of the criteria make sense, but i'm confused about 'Current remains </= 3C/32 when EDV2 or Battery Low % level is reached'. My typical discharge current is 0.5A, and my battery capacity is 1950mAhrs. In operation, the battery will discharge steadily at 0.5A until i hit my CVUV threshold. CVUV (~1%) will be set below EDV2 (~7%) and 'Battery Low %' (~3%).  Does this constraint mean i will never have a qualified discharge since 0.5A > 3C/32 (0.183A)? I would like to make sure i'm taking advantage of the learning capability of the chipset to modify FCC and track changes in capacity over time.

thanks again for all the help...

John

Hi Tom,

I have changed the CVUV to 9V as suggested. Now during discharge, when the first cell hits 3.0V i see the CVUV flag activate as expected. At that point however, my pack output voltage drops sharply by ~2.5V, but does not shut off. and i can still continue to draw a discharge current (0.5A in this test) from the pack. It seems as though the charge FET is turning off, however the discharge FET is staying on? the charge FET turning off could account for the sudden voltage drop as now the discharge current is flowing through the charge FETs body diode? I'm not sure how else to explain what i'm seeing.

I would have expected the discharge FET to turn OFF for a CVUV condition. is there something else I'm missing here?

thanks,

John

Hi Tom,

There is a CVUV bit, but that is a read only status bit in the Pack Status register indicating  a cell dropped below the CVUV threshold. However i don't see a CUVC bit (or anything like that) listed in the Pack Config Register. Pack Config contains DMODE, LED1, LED0, HPE, CPE, SM, CC1, CC0 bits. My Pack Config register is currently set to 0x26.

Other reg settings currently are:

gauge config = 0x49

misc config = 0BB9

[Device]
Name=bq2084
[Gas Gauge Flash Constants]
Version=01.43
Remaining Time Alarm=10
Remaining Cap Alarm=360
Design Voltage=10800
Specification Info=0031
MfrDate(yyyy-mm-dd)=2003-07-01
Serial Number=7
Cycle Count=21
Manufacturer Name=AURORA          
Device Name=SPHERES
Device Chemistry=LION
Pack Configuration=26
Gauge Configuration=49
Misc Configuration=0BB9
Deadband=9860
Self Discharge Rate=0.2
Electronics Load=0
Battery Low %=7.03
Near Full=200
Design Capacity=1950
Full Charge Capacity=1950
Cycle Count Thresh=1750
Charging Voltage=12600
Pre-charge Voltage=2000
Fast Charging Current=975
Maint Charging Curr=0
Pre-charge Current=975
Pre-charge Temp=9.6
Chg Inhibit Temp Low=0.0
Chg Inhibit Temp High=45.0
Fast Charge Term=100.00
Fully Charged Clear=95
Current Taper Thresh=125
Current Taper Vltg=225
Taper Termination Min=4.9
Maximum Over Chg=50
Charge Efficiency=100.00
Overload Current=5000
Overvoltage Margin=300
Clear Fail Current=100
Cell OV Set=4235
Cell OV Reset=4150
Cell UV Set=2400
Cell UV Reset=2700
Terminate Voltage=9000
Safety Voltage=13250
Chg Suspend Temp Hi=60.0
Chg Susp Temp Hi Rst=55.0
Over Temp Dsg=70.0
Over Temp Dsg Rst=60.0
Safety Temp Chg=75.0
Safety Temp Dsg=75.0
Chg Suspend Temp Lo=0.0
Shutdown Voltage=7900
VOC 75=11886
VOC 50=11430
VOC 25=11268
Emf (EDV0)=9000
EDV C0 (EDV1)=10364
EDV R0 (EDV2)=10681
EDV T0=0
EDV R1=0
EDV TC=0
EDV C1=0
Learning Low Temp=11.9
AFE OC Dsg Vltg=00
AFE OC Dsg Delay=0F
AFE SC Chg T/V=F0
AFE SC Dsg T/V=F0
AFE Vref=9783
Sense Resistor=0.0202
CC Delta=0.0000325
CC Offset=-12496
DSC Offset=43
ADC Offset=43
Temperature Offset=-3.9
Board Offset=0
AFE Fail Limit=10
Cell Bal Thresh=3850
Cell Bal Window=50
Cell Bal Minimum=10
Cell Bal Interval=20
Cell Imbalance Thresh=1000
Cell Bal Vcell Max=4500
Cell Bal Imax=50
Cell Imbalance Time=5
AFE Check Time=0
Sleep Current Thresh=10.0
Sleep Curr Multiplier=2
Sleep Time=10
Mfr Info 1=0000
Mfr Info 2=0000
Mfr Info 3=0000
Vmax Charge Vltg=4400
Voff Charge Vltg=4400
Von Charge Vltg=4200
Pulse Max On Time=60.00
Pulse Min Off Time=0.0000
Max Charge Time=16200
Pre-charge Detection=10
Chg Detection=25
Dsg Detection=-25
PF Status=2F
PF Flag=00
PF Config=00
PFIN Time=5
FET Fail Chg Curr=20
FET Fail Dsg Curr=-20
FET Fail Time=20
Chg OC Threshold=2925
Chg OC Time=6
Dsg OC Threshold=3000
Dsg OC Time=10
Fault Reset Time=30
Vpack Threshold=9091
Shutdown Timer=2
=

i've attached my current .GG file.

thanks,

John

Hi Tom,

Can you help me identify a way to shut off the DCG FET based on an undervoltage threshold? The bq2084 monitors voltage... I am just looking for a way to shut off the pack (shut off the DCG FET) when the pack votlage or a cell voltage gets too low.

Hi Tom,

I ran a calibration and then re-ran the test but got the same results. is there a flash setting to adjust the threshold for the charge current to prevent false triggers? can you send me the set of flash constants you used for your test (.GG file)? i'd like to see if i have something set incorrectly.

thanks,

John

Hi Tom,

Can you send me the .GG file you used for this test?

thanks,

John

John,

Here is the gg file frm the gauge that I was using. It was v143 firmware.

Tom

bq2084.GG