BQ40Z50-R1: Application issues

Hello,

In the image above, VC4 and VC3 will need to be tied directly to VC2 if there are only two cells in use. If the full schematic is shared, our team can review it.

Regards,

Anthony 

hi anthony

May I ask what problem would occur if VC3 and VC4 are not connected to VC2

Hello,

Grounding these pins would put them out of their recommended operating range since they rely on the voltage of the lower cell:

Grounding these pins will affect the performance of the gauge.

Regards,

Anthony

Hi anthony

Thank you very much for your response
Due to not paying attention to this issue during the previous schematic design, the current designs VC3 and VC4 are in a suspended state. Therefore, there are a few more questions that need to be consulted
1) What specific impact will VC4 and VC3 have on the gauge when suspended? Will the automatic shutdown of the gauge, capacity or battery level jumping to 0 affect normal use?
2) At present, even though VC3 and VC4 are in a suspended state, no abnormalities have been detected in the battery during normal use. It is uncertain whether this is due to testing not detecting them?
3) Under what specific usage conditions does the gauge  have an impact, such as high current, constantly changing large and small currents, high temperature, low temperature, or constantly changing high and low temperatures?
4) If the PCB has already started production and hardware changes cannot be made to the already produced PCB, can software adjustments solve this problem
5) If VC4, VC3, and VC2 are connected together in the future, are there any changes needed in the software configuration of the gauge
Thank you very much. I am looking forward to your reply again

Hello,

zhong susan said:

1) What specific impact will VC4 and VC3 have on the gauge when suspended? Will the automatic shutdown of the gauge, capacity or battery level jumping to 0 affect normal use?

When the gauge is configured, the DA Configuration is configured to represent the amount of cells in the stack. If the gauge is configured for 2 cells in this situation, there should be no issue with the firmware since it will ignore whatever is being seen from the VC3/VC4 pins. However, from the hardware side we do not spec the device for these pins to be grounded or floating. Since they are floating, they could not be in a steady state and potentially affect the hardware. Since cell balancing creates a bypass between the pins, we do not recommend this orientation,

zhong susan said:

2) At present, even though VC3 and VC4 are in a suspended state, no abnormalities have been detected in the battery during normal use. It is uncertain whether this is due to testing not detecting them?

Since the BAT pin is still being properly powered, the device will be functional.

zhong susan said:

Under what specific usage conditions does the gauge  have an impact, such as high current, constantly changing large and small currents, high temperature, low temperature, or constantly changing high and low temperatures?

Changing the load at a very high rate can affect the performance if the gauge is not configured correctly for it. For different temperatures, the gauge can be optimized for low and high temperatures, but quickly changing between the two can cause issues.

Regards,

Anthony

Holle 

Anthony said:

When the gauge is configured, the DA Configuration is configured to represent the amount of cells in the stack. If the gauge is configured for 2 cells in this situation, there should be no issue with the firmware since it will ignore whatever is being seen from the VC3/VC4 pins. However, from the hardware side we do not spec the device for these pins to be grounded or floating. Since they are floating, they could not be in a steady state and potentially affect the hardware. Since cell balancing creates a bypass between the pins, we do not recommend this orientation,

I didn't understand the meaning of this sentence

Anthony said:

Changing the load at a very high rate can affect the performance if the gauge is not configured correctly for it. For different temperatures, the gauge can be optimized for low and high temperatures, but quickly changing between the two can cause issues.

1) What is the specific phenomenon of the impact that changing the load at a very high speed may have? For example, is the capacity estimation of gauge meter incorrect?
2) A very high-speed load change, I can think, similar to the load current originally 3A, does it change from 3A to 20A in ns or us or ms time? If it changes from 3A to 20A within 1 minute, will it still affect performance;
3) If VC3 and VC4 are suspended, the rapid changes between high and low temperatures will also affect the performance of the gauge;

Hello,

zhong susan said:

I didn't understand the meaning of this sentence

In essence, leaving VC3 and VC4 grounding or floating will not affect the gauge from a firmware perspective since configuring the gauge for the correct amount of cells will ignore what is seen from VC3 and VC4. From a hardware perspective, we do not spec the gauge for this orientation, and do not recommend.

zhong susan said:

1) What is the specific phenomenon of the impact that changing the load at a very high speed may have? For example, is the capacity estimation of gauge meter incorrect?

Yes, this can effect the calculations that the gauge conducts. The amount of time it takes for the load to change is not as much of an issue, however the amount of time it stays can cause an issue. For example, if a pulsed load where 20A is only applied for 50ms, this can cause issues with the gauging performance. If the load goes from 3A to 20A quickly, however stays at 20 for 60s, this will be ok.

zhong susan said:

3) If VC3 and VC4 are suspended, the rapid changes between high and low temperatures will also affect the performance of the gauge;

This issue will be there even if VC3 and VC4 are correctly routed. We do not recommend rapid large changes in temperature.

Regards,

Anthony

Hi anthony

Thank you very much for your answer

Anthony said:

Yes, this can effect the calculations that the gauge conducts. The amount of time it takes for the load to change is not as much of an issue, however the amount of time it stays can cause an issue. For example, if a pulsed load where 20A is only applied for 50ms, this can cause issues with the gauging performance. If the load goes from 3A to 20A quickly, however stays at 20 for 60s, this will be ok.

Do VC4 and VC3 necessarily need to be connected to VC2 for applications with current changes similar to UAV?

Anthony said:

This issue will be there even if VC3 and VC4 are correctly routed. We do not recommend rapid large changes in temperature.

Is there a way to optimize the calculation capacity of the gauge for changes in environmental temperature? Is there a specific document that can be referred to

Hello,

zhong susan said:

Do VC4 and VC3 necessarily need to be connected to VC2 for applications with current changes similar to UAV?

Yes, we recommend VC4 and VC3 to be connected to VC2 in any 2S application.

zhong susan said:

Is there a way to optimize the calculation capacity of the gauge for changes in environmental temperature? Is there a specific document that can be referred to

The GPCRB tool can assist in low and high temperature optimization, however rapid temperature changes could still cause issues.

https://www.ti.com/tool/GPCRB 

Regards,

Anthony