BQ20Z95: bq20z95

Paul Classon

Part Number: BQ20Z95

I am using the BqEasy and EV2300 to program a Bq20z95 BMS. The factory specification sheet states both full charge capacity (0x10) and remaining capacity (0x11) maximum values as 65535 mah. At rate (0x04) max is +/- 32767 . The pack I am using has a capacity of 40000mah. Any value above 32767 mah causes a runtime error. Why will it not accept the full charge capacity as stated in the Ti spec sheet for this part?????

I await your best advice.

Paul.

over 8 years ago

0 TEC over 8 years ago

Expert 2475 points

TI does not recommend allowing RM and FCC to exceed 29000mAh for Impedance Track gauges as there is a potential that an overflow can occur in firmware. You can use capacity scaling to support packs where the capacity exceeds this value.

0 Paul Classon over 8 years ago in reply to TEC

Prodigy 50 points

Hi TEC, Sincere thanks for your prompt reply. OK the next question is, how and where do I implement capacity scaling.

Your best advice is greatly appreciated.

Many thanks in advance,

Paul

0 TEC over 8 years ago in reply to Paul Classon

Expert 2475 points

There is an applications report capacity scaling on the bq34z100 website. Search for SLUA760 on the TI website. You can use a 2x scale factor in your case and you will need to divided all of the current and capacity data flash parameters by 2x and then scale the current when you calibrate the pack. Currents and capacities will then be reported at 1/2 their actual values.

0 Paul Classon over 8 years ago in reply to TEC

Prodigy 50 points

Many thanks TEC.
Given the 34z100 is an impedance tracking device for a pack, ie a single voltage detection, how do I do this with a 4-cell pack. Do I calibrate all 4 voltage inputs to 50% of actual value? how does this impact on default cell chemistry file *.dfi??

0 Paul Classon over 8 years ago in reply to Paul Classon

Prodigy 50 points

perhaps I could just set AH capacity to 50% of actual and edit sense resistor value to half actual, leave voltages alone, what do you think??

0 TEC over 8 years ago in reply to Paul Classon

Expert 2475 points

You ill not need to use voltage scaling with the bq20z95. Just scale all of the current and capacity values. Here is a presentation that also covers the subject, although for the other device.

8407.Gauge Design Configurations for High Charge Discharge Rate Applications.pdf

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BQ20Z95: bq20z95