BQ34Z100-R2: Current/Energy Scaling via host. Can current scale and energy scale be different?

Steve Tecza

Part Number: BQ34Z100-R2
Other Parts Discussed in Thread: BQ34Z100, BQSTUDIO

Tool/software:

The question is, how is scaling via the host supposed to work? what am I missing? Do I have to use the same scale factor for everything?

I need the design capacity to be set up to 3,276Ah and be adjustable in the field, and if I set current scale to the same 100x, then my current resolution drops to 100mA, which is not great.

The Details:

Current and energy is scaled by my host controller. (because as we established previously, the BQ34Z100-R2 0x0202 firmware is defective and the internal scaling does not work)

Current scale factor is 20x

Energy scale factor is 100x

I am testing a 4 cell LiFePO4 battery. The nominal capacity is 100Ah. (design capacity is set with 100x scale factor, so the chip has 1000mAh)

During the learning cycle the full charge capacity was reported as 167Ah after resting at full charge (started from resting at empty, UpdateStatus is now 0x05)

While discharging at 16.5 amps (1/6C), the remaining capacity is dropping at about 5x the expected rate.

After one hour of discharging at 16.5A, remaining capacity has dropped by 82Ah, which is right at 5x more than expected. (steady drop, no big jumps that I saw)

The BQ34Z100 is reporting the correct current and battery voltage.

I can see that this makes sense because the battery is stored as 1000mAh, and the current is measured as 825mA, which would result in the battery capacity changing by 5x expected.

HOWEVER The measured capacity was NOT 5x more than expected- 167Ah vs 100Ah

I have current scale applied to the following:

AverageCurrent 0x0A
Current 0x10
PassedCharge 0x1C
AveragePower 0x26
ChargeCurrent 0x32
QmaxPassedQ 0x6E
CC_Gain (flash page 104, offset 0, read and write)
CC_Delta (flash page 104, offset 4, read and write)
Sleep Current (flash page 68, offset 2, read and write)

I have Energy Scale applied to the following:

RemainingCapacity 0x04
FullChargeCapacity 0x06
AvailableEnergy 0x24
DesignCapacity 0x3C
DesignCapacity (flash page 48, offset 11, write only)

2 months ago

0 Alan Frias 2 months ago

TI__Mastermind 26265 points

Hello Steve,

This question has been assigned and a response is being worked on.

Thank you,
Alan

0 Diego 2 months ago in reply to Alan Frias

TI__Mastermind 26175 points

Hi Steve,

I don't believe you are scaling correctly.

For R2 FW, if your discharge/charge current does not exceed 32ah, then you do not need to scale the current reading.

Internal scaling factors (current scale, energy scale, voltage scale) are used to scale parameters in the gauge so that they fit within the parameter limits. So, for example, the max value for design capacity without scaling is 32767mah. If you would like to use a 60000mah battery, a scaling factor of 2 must be applied. For current scale you will enter a value of 2, for design capacity you will enter a value of 30000mah (2*30000=60000mah). You will then need to divide all parameters reported in BQstudio in mah/ah/ma/etc by 2. This process is the same for energy scale and voltage scale, for energy scale all parameters reported in W/Wh/cwh and for voltage scale all parameters reported in V/mV.

Steve Tecza said:
I am testing a 4 cell LiFePO4 battery. The nominal capacity is 100Ah. (design capacity is set with 100x scale factor, so the chip has 1000mAh)

This is not necessary, you can use a much smaller scaling factor. In general, we do not recommend exceeding a scaling factor of 10 unless absolutely necessary. I recommend using the smallest scaling factor possible.

Please make these corrections and then share your .gg file and a log file of any errors, if errors in SOC/FCC/etc still continue.

Regards,

Diego

0 Steve Tecza 2 months ago in reply to Diego

Prodigy 130 points

We established that the -R2 firmware is defective and the internal scaling factors do not work at all:

e2e.ti.com/.../bq34z100-r2-current-scaling-confusion--currscale-does-almost-nothing

0 Diego 2 months ago in reply to Steve Tecza

TI__Mastermind 26175 points

Hi Steve,

Current scale does not scale the current reading, this needs to be done through calibration. Current scaling is used to scale parameters in the gauge so that they fit within the parameter limits.

This thread describes how to scale the current through calibration. (+) [FAQ] BQ34Z100-G1: Current/Capacity Scaling - Power management forum - Power management - TI E2E support forums

Regards,

Diego