BQ40Z50-R1: bq40z50-r1 vs bq76920

Viraaj Somayajula

Intellectual 295 points

Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQ76920, LM34936, , BQ40Z50-R2, BQ40Z60

Hi,

I am designing a battery management system for a 3S or 4S battery pack. Requirements are as follows:

Programmable cut off voltage and over voltage protection.

Communication over I2C bus. [All the communication over I2C bus]
Battery percentage, battery voltage, current reporting.
Battery wear out/deterioration reporting.
Supports 3S – 4S battery configuration
Over current cut off

Separate charging and discharging ports.
Even while charging the maximum output voltage should not exceed 16.8V.
I have considered the following options for the monitoring and management controllers:
BQ76920 3s-5s configuration, SOC for interfacing with BQ76920 on one side and external system communication on the other side (I2C preferable) and as separate regulated port, LM34936 for regulation to a constant voltage (14.2V).
How does bq40z50-r1 compare against this choice in the mentioned scenario? Are there any other parts which would be advisable?

over 5 years ago

0 Wyatt Keller over 5 years ago

TI__Guru** 105760 points

Hello,

The BQ79620 doesn't calculate the battery percentage, you would need to derive the percentage using a MCU.

This E2E Explains briefly: https://e2e.ti.com/support/power-management/f/196/t/777284?BQ76920-Need-information-regarding-BQ76920

The BQ40z50-R1 would be able to give you the SoC reading directly and more accurately.

Sincerely,

Wyatt Keller

0 Rushi_Dalal over 5 years ago

TI__Intellectual 2025 points

Hi Viraaj,

Please look at BQ40z50-R2. To your points, yes can set OVP, UVP via register settings. This device uses SMBus communication. It can also report battery %, voltage, current, and other battery information. There are two separate protection FETs for charging and discharging.

The technical reference manual will be able to highlight which registers you can set these parameters: https://www.ti.com/lit/ug/sluua43a/sluua43a.pdf

The bq769x0 parts you mentioned are monitors, not gauges. Therefore, it won't provide SOH/SOC information.

Thanks,

Rushi

0 Viraaj Somayajula over 5 years ago in reply to Wyatt Keller

Intellectual 295 points

Thank you Wyatt. That helped.

0 Viraaj Somayajula over 5 years ago in reply to Rushi_Dalal

Intellectual 295 points

Hi Rushi,

Thank you for clarifying those things. I have gone through the bq769x0 datasheet well, but not yet have gone through the BQ40z50-R2 datasheet completely yet. So, please help me clarify a few more things.

According to what you said, most of the features offered by bq769x0 series are offered by BQ40z50-R1 as well and BQ40z50-R1 includes gas gauging (and no need for a management controller). Am I right?

Are there any advantages of using bq769x0 as compared to BQ40z50-R1 for the scenario mentioned?

What about the simultaneous charging and discharging scenario?

What are the advantages of BQ40z60-R1 (with integrated charger)?

Approximately how long before NRND(Not recommended for new designs)?

Thanks

Viraaj

0 Rushi_Dalal over 5 years ago in reply to Viraaj Somayajula

TI__Intellectual 2025 points

Hi Viraj,

That right, BQ40z50-R2 doesn't need a separate management controller. BQ40z50-R1 is the older counterpart of BQ40z50-R2. These devices will continue to be in production, there is no plan for NRND or EOL. If you use bq769x0, then you will need an MCU to derive state of charge by writing your own code. A gauge is eliminating this software overhead for you since the gauging algorithm in integrated inside the chip.

BQ40z60 is not recommended because we have seen strong EMI emissions due to interference from the switching charger.

Thanks,

Rushi

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BQ40Z50-R1: bq40z50-r1 vs bq76920