BQ20Z40 erroneous Lifetime Max Cell Temperature issue

David Tung

Other Parts Discussed in Thread: BQ20Z40, BQ40Z60

We have a new pcb using bq20z40. I setup and calibrated several of our boards and ran a charge and discharge cycle with the lifetime data enabled. I get an erroneous Max Cell Temperature of 127 deg C recorded. If I reset the Lifetime data and setup data logging while monitoring temperature of all thermistors and Max Cell Temperature. Temperatures all read normal (less the 35deg C), but I still get a Lifetime Max Cell Temperature recorded as 127dec C. There are no over temperature flags set.

Any idea what can cause this?

over 8 years ago

0 Swaminathan Ramanathan75031 over 8 years ago

TI__Expert 6575 points

Hi,
Do you have one or two external temp sensors? Can you also please tell me the settings of TEMP0 and TEMP1 on the "Operation Cfg A"?
Regards,
Swami

0 David Tung over 8 years ago in reply to Swaminathan Ramanathan75031

Prodigy 90 points

I am sorry. I just noticed that I have the bq part number wrong. The problem I am having is with the bq40z60. Shall I repost it correctly?

0 Swaminathan Ramanathan75031 over 8 years ago in reply to David Tung

TI__Expert 6575 points

Hi David,
On the bq40z60 it will be the "Temperature Enable" and "Temperature Mode". Can you please tell me the settings for these? Maybe one of the sensors that is not being used is enabled on these settings.
Regards,
Swami

0 David Tung over 8 years ago in reply to Swaminathan Ramanathan75031

Prodigy 90 points

Swami,

In answer to your request for settings:

Swaminathan Ramanathan75031 said:

On the bq40z60 it will be the "Temperature Enable" and "Temperature Mode". Can you please tell me the settings for these? Maybe one of the sensors that is not being used is enabled on these settings.

Temperature Enable has the following bits set (red) TS4, TS2, TS1, TSInt. We are not using TS3. There is a 10K resistor in place of the thermistor so that the LEDs act correctly.

Temperature Mode has only TSInt Mode set.

Regards,

David

0 Swaminathan Ramanathan75031 over 8 years ago in reply to David Tung

TI__Expert 6575 points

Hi David,
The setting seem correct. If you read TS3, does this read the 127degC? Can you post the log file? I will try to take a look.
Regards,
Swami

0 David Tung over 8 years ago in reply to Swaminathan Ramanathan75031

Prodigy 90 points

Swami,

I ran a discharge and charge cycle while logging with the Battery Management Studio. The lifetime Max Cell Temp has not gone to 127 deg C yet, however, there are some log entries that are interesting. Most of the log entries are OK, but there are sporadic erroneous entries where TS3 is reporting temperature 30 to 80deg C too low. Lifetime Max cell is currently showing 37, Min Temp Cell is showing 23 and Max Delta is showing 85.

How do I post the log file for you to see?

David

0 David Tung over 8 years ago in reply to David Tung

Prodigy 90 points

Swami,

Quick updated. After running another discharge cycle without logging, the Lifetime Max Temp Cell now reads 125 deg C, Min Temp Cell reads 22 deg C and Max Delta Cell Temp reads 127 deg C.

David

0 Swaminathan Ramanathan75031 over 8 years ago in reply to David Tung

TI__Expert 6575 points

Hi David,
There should be a "Use rich formatting" link to the right below the reply box. You can attach files when you select rich formatting. Please post the log file, I will take a look.
Thanks,
Swami

0 David Tung over 8 years ago in reply to Swaminathan Ramanathan75031

Prodigy 90 points

Swami,

Thank You. Below is the log file.

charge.log

David

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BQ20Z40 erroneous Lifetime Max Cell Temperature issue