AFE requirement

Matt Tsai

Other Parts Discussed in Thread: BQ76930, BQ76940

We want to develop off-road motor's battery BMS.
The average current is 30A, but the peak current is 200A(last 3~5 sec).
That is, need to ensure D_FET is on when the discharge current is 200A(last 3~5 sec).
Also, the required cell number is 13S.
Which AFE satisfy such requirement?

Thanks

over 6 years ago

0 Miguel Angel Rios over 6 years ago

TI__Expert 4640 points

Hi Matt,

Please use our parametric table on the monitor page located here www.ti.com/.../overview.html

Thanks

Miguel

0 Matt Tsai over 6 years ago in reply to Miguel Angel Rios

Intellectual 330 points

Hi
Is there any AFE you suggest?

We use two BQ76930 AFEs in our previous BMS(for eScooter).
BQ76930 has the ability to satisfy the requirement?

Thanks

0 Matt Tsai over 6 years ago in reply to Miguel Angel Rios

Intellectual 330 points

TI AFE BQ76930 OCD protection can be set to 200A?
How to achieve it?

Thanks

0 Miguel Angel Rios over 6 years ago in reply to Matt Tsai

TI__Expert 4640 points

Hi Matt,

bq76930 is only for up to 10S, please look into the bq76940 for up to 15S. You will have to set it based on your sense resistor and the threshold. The datasheet should explain this.

Thanks

Miguel

0 Matt Tsai over 6 years ago in reply to Miguel Angel Rios

Intellectual 330 points

Hi Miguel,
We use two bq76930 to satisfy 13S.

You will have to set it based on your sense resistor and the threshold.
==>You mean we can set OCD protection to 200A?
Is there any limit for the maximim OCD/SCD protection current?

Thanks,
Matt

0 Frank Hsu94 over 6 years ago in reply to Matt Tsai

Prodigy 130 points

Hi Miguel,
According to the datasheet of BQ76930 , the max and min value for SCD and OCD as the following (if we choose RSNS=1)
SCD is 44mv to 200mv
OCD is 17mv to 100mv
Does it means if we using sense resistor to 0.65mR then we can let SCD max threshold value to 200mV/0.9mR = 222A and OCD's max threshlld value will be 100mv/0.9mR = 111A

Is it correct ?

0 Miguel Angel Rios over 6 years ago in reply to Frank Hsu94

TI__Expert 4640 points

Hi Frank, Matt,

In general the calculation is correct. Keep in mind that you will have to take into account the tolerances when you do this calculation based on the sense resistor value you choose.

Here is another post that talks about this same subject.

e2e.ti.com/.../2635131

Thanks

Miguel

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AFE requirement