• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 646 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ33100 measurement of Capacitance and ESR and communication

Zhenya Cheredinova
Prodigy 40 points
Other Parts Discussed in Thread: BQ33100

I am using BQ33100 (Device Type = 0x3100,  Firmware Version = 0x0015).

Current load = 0.5 Ampere

The bq33100 can be used to monitor 5 capacitors in series.

 ELECTRICAL CHARACTERISTICS OF SUPER CAPACITOR 

Type: ESHSR-0025C0-002R7

Capacitance = 25 F

ESR = 15÷25 mOhms

When working with bq33100, I had a few questions. 

1. CAPACITANCE

Why the calculated Capacitance differ from the real Capacitance?

Capacitance measured by the bq33100 is 44 ÷ 50 F

Capacitance measured on the oscilloscope is 5 Seconds * 0.5 Ampere / 0.5 V = 5.0 F

 

2. ESR

Why the calculated ESR differ from the real ESR?

ESR measured by the bq33100 is 126÷182 milliOhms

ESR measured on the oscilloscope is 51 mV / 0.5 Ampere = 102 milliOhms

 

3. CHARGE

Why is uneven charge of supercapacitors? First supercapacitors charges faster than the others and it is balanced for much longer time?

For example, after Learn: ΔV of CapacitorVoltage5...1 ≥ 200 mV and balancing discharge per 5 mV/hour.

 

4. EXTENDED SBS COMMANDS

Why some extended SBS commands are available via ManufacturerAccess, and others extended SBS commands as usual SBS Command?

For example:

Name

Format

FETControl

SBS: FETControl(0x46)

SafetyAlert

SBS:ManufacterAccess(0x00): SafetyAlert (0x50)

SafetyStatus

SBS:ManufacterAccess(0x00): SafetyStatus(0x51)

OperationStatus

SBS: OperationStatus(0x54) or

SBS:ManufacterAccess(0x00): OperationStatus(0x54)

SystemVoltage

SBS:ManufacterAccess(0x00): SystemVoltage(0x5a)

UnSealKey

SBS: UnSealKey(0x60)

ManufurerInfo

SBS: ManufurerInfo (0x70)

 

5. SBS MAC COMMANDS

Why can't I read some SBS commands?

For example, when reading I get such values:

SBS Cmd

Name

Value

0x0003

Hardware Version

0x00FF

0x0004

DF Checksum

0xFFFF

0x0021

Lifetime and Capacitor Balancing Enable

0x00FF

0x0022

IF Checksum

0xFFFF

0x0036

Read AD Current

0xFFFF

 

Why can't I write the command 0x0021 (Lifetime and Capacitor Balancing Enable)?

  • 0
    TI__Expert 6470 points

    Incorrect measurements could be caused by a variety of issues including mis-calibration, inappropriate learning load, improper connections etc. I suggest you scope what is happening during the learn cycle as a method of investigation. Attached is an application report that may be helpful.6710.bq33100 Top Ten Design Considerations.pdf

  • 0 in reply to Doug Williams4811
    Prodigy 40 points

    I am using a 5S1P stack composed of 25 F capacitors (Model: ESHSR-0025C0-002R7; ESRavg  = 15 mOhm).

    The total capacitance = 25 / 5 = 5 F.

    ESR of the total stack = 15 * 5 = 75  mOhm.

    Therefore:

    DF:Configuration:Registers:OperationCfg = 0x0448

    DF:SystemData:Data:DesignCapacitance = 5 F

    DF:SystemData:Data:Init1stCapacitance = 5 F

    DF:SystemData:Data:Capacitance = 5 F

    DF:SystemData:Data:DesignESR = 75 mOhm

    DF:SystemData:Data:InitialESR = 75 mOhm

    DF:SystemData:Data:ESR = 75 mOhm

    If the level of the charge is Charge Level Nominal, voltage rises to 10687 mV.

    If the level of the charge is Charge Level A, voltage rises to 11303 mV.

    If the level of the charge is Charge Level B, voltage rises to 11416 mV.

    If the level of the charge is Charge Level Max, voltage rises to 11530 mV.

    Therefore:

    DF:ChargeControl:ChargeCfg:ChgVoltage = 10700 mV

    DF:SystemData:Data:DesignVoltage = 10700 mV

    DF:Monitoring:ChargingVoltage:VChgNominal = 10700 mV

    DF:Monitoring:ChargingVoltage:VChgA = 11300 mV

    DF:Monitoring:ChargingVoltage:VChgB = 11400 mV

    DF:Monitoring:ChargingVoltage:VChgMax = 11500 mV

    DF:Monitoring:ChargingVoltage:VLearnMax = 11500 mV

     

    If I understand correctly, since as the capacitor voltages and the charging current are displayed close to the real values, calibration cannot spoil a measurement.

    The learning process takes place in the sequence described in the datasheet and corresponds to the schedule in the figure 1.

    I read the bq33100 Top Ten Design Considerations.pdf  and haven't found a suitable answer.

    What am I doing wrong?

    Sometimes after Learn, there is an error in the 12 bit SafetyStatus, what it might mean?

  • 0 in reply to Zhenya Cheredinova
    TI__Expert 6470 points

    Could it be that you have a load connected to the supercap stack when the learn cycle is run? There should be no system load, only the learning circuit.

    Did you modify the EVM to arrive at the 4 desired charging voltages, or is this a custom design? If its a custom, are you sure that the learning load is implemented correctly?

  • 0 in reply to Doug Williams4811
    Prodigy 40 points

    During normal operation, processor consumes 20 mA of super capacitors.

    The evaluation module (EVM) is made by your scheme.