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questions re: bq2084 / bq29312a chipset

Other Parts Discussed in Thread: BQ29312A, BQ29312, BQ2084-V143, BQ2083

Hi,

I posted the below question as a reply to an earlier thread. i apologize for posting twice, just wanted to make sure i'd submitted it properly.

I'm trying to debug a custom PCB that includes the bq2084 and bq29312a chipset. hardware. I'm getting what i think are some unusual responses from the chipset and I'm wondering if we have something programmed incorrectly. One example.... the cell undervoltage shutoff seems to be working (DCG FET turns off when a cell goes too low), but i can't get the FET to turn back on when the cell rises above the reset voltage. I can get the FET to turn back on if I powercycle the chipset, so it almost seems like the undervoltage sets a flag that needs to get reset in SW?

I also can't get the CHG FET to turn off when a cell voltage rises too high

This is a standard 3-cell series li-ion pack... can i send you a screen capture of the bq2084/bq29312a register set and see if there's something in there that needs to be changed?

thanks,

John

  • John
    I have not heard of any problems with the DSG FET turning on at the CUV reset threshold. Can you provide a screenshot of the data flash parameter screen and I will try to check it.
    Tom
  • 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

  • John
    My EVM is broken, so I ordered a new one to test your setup. It will take a few days.
    Tom
  • 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.

    Data_Flash_3_19.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
    =
    
    after you've had a chance to try it on your hardware, is there a more direct way we could communicate? to reduce iteration time if needed?

    thanks again,

    John

  • also, let me know if you need any further info (schematics, cell p/n, etc...) thanks!
  • 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 John,
    Sorry, but I've been in Europe for a couple weeks. To make further progress on this, I'm going to need a log from the EVSW that demonstrates the unusual behavior.
    Regards,Doug
  • 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

    SPH_05-11-15.txt
    [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 Doug,

    I must amend that last post slightly... when he voltage goes below CVUV, the DCG FET turns OFF, however it does not turn back on when the voltage goes back above CVUV Reset. the CHG FET still does not turn OFF when CVOV is set.

    thanks,
    John
  • Also, can you tell me what the 'Battery Status' bits mean? e.g. OCA, TCA, INIT, DSG etc.... i can't find this information in the literature
  • Its funny, table 10 is blank regarding DSG FET behavior in CVUV. Did you see the small notes under the table? If you have too much discharge current flowing the charge FET will not open in order to protect its body diode.
  • You can search the datasheet for "batterystatus" and find it all. For example, the table on page 43 of the bq2084-V143 datasheet.
  • Hi, during production i accidentally sealed the bq2084 chipset. How do i unseal it using the EV2300? i am running the bq2084 evaluation software version 2.1.0. thanks...
  • Please provide an email address and I will send the Unseal codes.
  • email address is jmerk@aurora.aero. Can you also include the procedure? i looked on the forum (for example) at slua421a but this seems to use a different version of the evaluation SW and or HW. thanks very much!!
  • 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

  • The voltage related parameter that can be used to turn of the DSG FET is the CVUV threshold. You can set it closer to the Termination Voltage to turn the FET of at that point. You are correct that CVUV is cell based and can result in a premature termination, if the cells are out of balance.
  • 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

  • John
    The criteria should be that the |Current| >3C/32. They must have used the interpretation that larger negative currents are smaller numbers. e.g. -9 < -8. You should be okay.

    Tom
  • 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

  • John
    Do you have the CUVC bit set in the Pack Config register. The DSG FET should disable, if this this is set and the voltage drops below the threshold. I bench tested it and it worked.
    Tom
  • 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

    SN5_02-26-16.txt
    [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

  • John
    I rechecked the bq2084 datasheet and it does not say that the DSG FET will be disabled due to an under voltage condition. I do not have a bq2084 EVM at my desk, but I was using a bq2083 EVM in the previous test. The bq2083 will disable the DSG FET due to an under voltage condition.

    Tom
  • 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.

  • John
    I found a bq2084 EVM and tested CVUV and found that it does disable the DSG FET. I found that a charge current will turn the FET back on. Make sure that the Offset Calibration has been run so that there is no "false" charge current after the DSG FET has been disabled.
    Tom
  • 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

  • Hi Tom,

    Been awhile since we talked. the .GG file you sent me in March seemed to make things better... but i do have one more question.

    The bq2084 datasheet indicates VpackThreshold must be greater than Shutdown voltage + 6%. However in the example .GG file you sent and in the datasheet, the default value for VpackThreshold is 2000 cnts which is equal to 1.87 V? For a 3-cell pack, i would expect to set VpackThreshold to ~7500 cnts...... 7500cnts * .935mV/cnt > 2.2V/cell * 3 cells + 6%.

    can you clarify how to properly set VpackThreshold for a 3-cell li-ion battery?

    thanks!
    John
  • .....or perhaps a better question is what registers influence the Shutdown feature and how do i program them to shutdown the pack when the voltage gets too low? pg 26-27 of the bq2084-v142 datasheet indicates "The bq2084-V143 goes into shutdown, in which all FETs are turned off and the pack electronics are powered down (including the bq2084-V143), when SBS.Voltage() falls below Shutdown Voltage DF 0x7c-0x7d and Voltage at the Pack pin is less than VPACK threshold (DF 0x131, 0x132) both for 2 consecutive samples (1 to 2 s)"

    At the moment, i have the Shutdown register programmed to 8100mV and the VPACK Threshold set to 8050 cnts. In my latest testing, i can now get the pack to shut off during discharge when CVUV is activated. However, if the pack is not plugged into a charger right away and the quiescent current of the pack electronics continue to discharge the battery, I'd like to use the Shutdown feature to "power down the pack electronics" to put it in it's lowest power state until it's plugged into a charger.

    thanks,
    John