bq78250 Question

Pratik Das

Part Number: BQ76940
Other Parts Discussed in Thread: TIDA-00792, BQ78350

Dear TI Team,

I am using the BQ76940 chip to make a BMS for my battery pack. the pack consists of 13 cells in series and 100AH capacity.

In the schematic the maximum output current is mentioned to be 20A. I would like to have my maximum current greater than 50A.

What are the specific changes i should do in the schematic to achieve that Or the reference design is good enough for 50A output current?

I have checked the MOSFETs, they are designed for high current (200A). the sense register is 1mOhm. it should be ok for 50A. Am I missing something here.

With kind regards,

Pratik

over 8 years ago

0 Miguel Angel Rios over 8 years ago

TI__Expert 4640 points

Hi Pratik,

Can you please first take a look at the datasheet application section on page 46 section 8.2.2.1 "Step-by-Step Design Procedure"? Then come back if you have trouble with the instructions.

Thanks

M

0 WM5295 over 8 years ago in reply to Miguel Angel Rios

TI__Guru 54715 points

Hi Pratik,
Regarding the TIDA-00792 design and higher current, consider the component power ratings and thermal management. For example 50A in the 1mOhm sense resistor gives 2.5W. Once you select resistors for the power rating, be sure you can get the heat out of the components.

0 Pratik Das over 8 years ago in reply to Miguel Angel Rios

Prodigy 160 points

Thanks M.

I will have a look and get back to you if i have any questions.

With kind regards,

Pratik

0 Pratik Das over 8 years ago in reply to WM5295

Prodigy 160 points

Thank you. Yes that is very important. I am checking them out now. will get back to you if i have any specific questions.

With kind regards,
Pratik

0 Pratik Das over 8 years ago in reply to Miguel Angel Rios

Prodigy 160 points

Dear Mr. Rios,
I have another question related to the controller BQ78350DBTR-R1. in the technical data sheet, it is mentioned that, the maximum charging current and discharging current that can be used for this controller is 32.767A. is it for some specific case or it's a limitation from the chip?

with kind regards,
Pratik

0 Pratik Das over 8 years ago in reply to WM5295

Prodigy 160 points

Dear Sir,
I have another question related to the controller BQ78350DBTR-R1. in the technical data sheet, it is mentioned that, the maximum charging current and discharging current that can be used for this controller is 32.767A. is it for some specific case or it's a limitation from the chip?

with kind regards,
Pratik

0 Miguel Angel Rios over 8 years ago in reply to Pratik Das

TI__Expert 4640 points

Hi Pratik,

I noticed your questions are not related to the bq76940 Analog Front End, but mostly related to how the gauge works with the bq76940. Therefore, i have changed your title and moved your question to the gauge.

0 Onyx Ahiakwo over 8 years ago in reply to Miguel Angel Rios

TI__Guru* 76230 points

Hi Pratik,
The gauge reports current in mA.. so at 32A, that is 32000mA. A register has 2^16 bits, which is 65536. Given current is a signed integer to prevent overflow hence the limit is capped from -32000mA to +32000mA. You can fool the gauge for to measure higher currents by following the app note below. Though written for a different gauge, the method is applicable to the bq78350

www.ti.com/.../slua760.pdf

thanks
Onyx

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