BQ40Z60EVM-578: BQ40Z60EVM-578-low precharging current

LIAN DAI59

Part Number: BQ40Z60EVM-578
Other Parts Discussed in Thread: BQ40Z60

Hi Guys,

I'm using TI BQ40Z60EVM-578 evaluation board to charge our 4-cell Panasonic NCR18650B 3350mAh battery. The load is a 40ohm resistor load.

The first two charing and discharging cycles look pretty. The battery will be fully charged and the stop charge voltage is 4200mV. Once it's discharged, the charger will stop at 3000 mV. Everything seems normal.

Until today, the fully discharged cell pack start to be charged. However, the precharging time took about 4 hrs with current to be around 15mA, which should be 250 mA by default. The precharging curernt is still 15mA after 4 hrs. could you figure out why?

Thanks

Lian

over 8 years ago

0 ThomasCosby over 8 years ago

TI__Guru 73830 points

It looks like you have some faults present based on the SS flag being set and the FETs being disabled. Can you provide a picture showing all of the Bit Registers?

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

Hi Tom,
thanks for your quick response. I just attached what you need. It seems the forum doesn't allow to attach the CVS file exported from the data memory.
LianDATA_MEMORY_BQ40Z60 low precharging current.xlsx

0 jury noname over 8 years ago

Intellectual 765 points

>The precharging curernt is still 15mA after 4 hrs. could you figure out why?
If you schematic based from typical datasheet, you can replace the resistor into precharge chain from 300 Ohm to ~20 Ohm (or recalculate to current for you need)

e2e.ti.com/.../1975753
"I would recommend reducing the series PCHGFET resistor value. Assuming your Charger voltage is 8400mV and BAT pin voltage is 4800mV based on your log file. If there's 300-ohms resistor in series with PCHGFET then the precharge current is (8400mV-4800mV)/300-ohms => 12mA. To achieve 200mA precharge current the series resistor needs to be <18-ohms for the same charger voltage."

0 ThomasCosby over 8 years ago in reply to jury noname

TI__Guru 73830 points

The bq40z60 version 15 firmware has a big that prevents the external pre-charge FET option from working properly, so it should not be used. The gauge can support lower currents for pre-charge conditions using the CHG FET. The user will need to set the pre-charge current in the data flash and set the LCHGM and LCHGS bits low in the Charging Configuration register.

0 LIAN DAI59 over 8 years ago in reply to jury noname

Intellectual 590 points

Hi Jury,

Thanks for your reply. However, the BQ40Z60 doesn't have external pre-charging resistor to regulator the current, which is set by internal DAC register.

0 jury noname over 8 years ago in reply to LIAN DAI59

Intellectual 765 points

Hi Lian!

you is partly right.. But bq40z60/EVM have precharging resistor (R1) - see attach. And this function don't work in current firmware - read answer from Thomas..

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

Hi Tom,

"The bq40z60 version 15 firmware has a big that prevents the external pre-charge FET option from working properly, so it should not be used." what do you mean by BIG? Typo?

are you trying to say the version 15 firmware can't handle the external pre-charge FET properly.

I did upgrade the version 13 to version 15 and reset the chip, and the issue was fixed. However, I'm not sure if the issue was fixed by resetting or firmware update.

Lian

0 Damian Lewis over 8 years ago in reply to LIAN DAI59

TI__Mastermind 34775 points

Hi Lian,

Tom meant "BIT." Version 15 disables the use of the pre-CHG FET and uses CHG FET for charging during the pre-charge phase, once the pre-charge current is set in the data flash as Tom mentioned above.

0 ThomasCosby over 8 years ago in reply to Damian Lewis

TI__Guru 73830 points

Lian
I meant "bug". There is a firmware bug that prevents the external pre-charge FET option from working.
Tom

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

2061.DATA_MEMORY_BQ40Z60 low precharging current.xlsx

hi Tom,

today I encountered with the same issue.

here is what I did. I've set LCHGM and LCHGS in charging configuration. I intentionally discharge the battery to 2600 mV by setting recovery voltage to be 2600 mV in CUV(external power adaptor was shut off).

However, once I turn on the external power supply, the charger can't charge the battery and supply current to the load(20 ohm resistive load).

0 ThomasCosby over 8 years ago in reply to LIAN DAI59

TI__Guru 73830 points

There is an ACOV fault that prevents the charger from turning on. Also, there is a firmware bug that prevents the high precision current control from working properly, so the LCHGM and LCHGS bits need to be set to 0.

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

I've set the LCHGM and LCHGS to be 0, still not charging. did i forget something? or should i wait until the next firmware release?

We plan to use this chip for our next generation product, so addressing the bug will be important to us.

Thanks.

Lian

0 ThomasCosby over 8 years ago in reply to LIAN DAI59

TI__Guru 73830 points

Please send a log file showing the use case that is not working and an srec file exported from your pack. I will check them.

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

Hi Tom,

here are the files you need.

I don't have log file since I didn't record the log when device is working. What I attached here is current none precharging case log. It's for reference only.

I was trying to reset the chip using the command provided by the studio, but it seems not working.

BQ40Z60 NONE CHARGING.zip

0 ThomasCosby over 8 years ago in reply to LIAN DAI59

TI__Guru 73830 points

The log data shows that you still have a ACOV fault present and this will keep the charger off. The ACOV threshold is set to 20000mV on the data flash. Is you AC Adapter voltage higher than this? If it is not, then you may need to calibrate the pack voltage. To do this, turn the charge enable off and go to the Calibration screen. Apply a voltage to the VACP input. Enter this voltage into the Applied PAck Voltage field and calibrate the voltage. This should solve the ACOV fault and allow you to charge.

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

The AC adapter voltage is 19.94V, so i set the ACOV threshold to be 19000mV and recovery to be 18000mV. still not charge so far.

0 ThomasCosby over 8 years ago in reply to LIAN DAI59

TI__Guru 73830 points

The ACOV threshold must be set higher than the adapter voltage. Try setting it to 20000mV.

0 LIAN DAI59 over 8 years ago in reply to LIAN DAI59

Intellectual 590 points

i set the ACOV threshold to 21000mV and recovery to be 20300mV. It does reset ACOV flag, but still not charge.

DATA_MEMORY_BQ40Z60.gg.csv.zip

0 ThomasCosby over 8 years ago in reply to LIAN DAI59

TI__Guru 73830 points

Will the device start charging, if the cell voltages are above the pre-charge recovery threshold? I can try testing your gg file in my pack on Monday.

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

I've set the ACOV recovery voltage to 8000mV, which is lower than the battery pack voltage 8848mV, still not seeing charging.

I also have another question about the voltage calibration, I assume the Applied battery voltage is the voltage between the cathode of cell 1 and the anode of cell 4(we only have four cells), and applied pack voltage is the voltage of external power supply, is that right?

Thanks

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

Good morning, Tom

is there any update?

Lian

0 ThomasCosby over 8 years ago in reply to LIAN DAI59

TI__Guru 73830 points

Lian,
You do have an OC fault set, so this will disable charging. You can try resetting the device to clear the fault. I just noticed that you are using v13 firmware. The external pre-charge FET feature and LCHGM and LCHGS feature works with this firmware version. I thought that you were using the latest firmware, v15.
Tom

0 LIAN DAI59 over 8 years ago in reply to ThomasCosby

Intellectual 590 points

Hi Tom,

I checked the firmware version, and it should be v15. Initially, it was v13, but I upgraded it to be v15. As for the OC, what I see here is 0, so it means no fault?

You may looked at my old attachment and have the wrong reading. The newest attachment is here. Also, resetting the device doesn't fix the charging issue.

1651.DATA_MEMORY_BQ40Z60.gg.csv.zip

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BQ40Z60EVM-578: BQ40Z60EVM-578-low precharging current