Hello TI Engineer,
I almost done with my schematics using BQ7791514.
Below are the requirements:
|
Battery Pack requirement |
External Charger used |
Cells requirement |
|
Nominal Voltage = 12.8V |
Voltage = 14.6V |
Chemistry = LifePo4 cell |
|
Capacity = 6A |
Current = 2.1A |
Nominal Voltage = 3.2V |
|
Peak current = 1.2A |
|
Capacity = 6Ah. |
|
|
|
Cell Configuration = 4 series |
Please review my schematics:
It would be great help, If you can stress on below points.
1. External balancing circuit:
The internal balancing current [3.6V/ (1.5K+12+1.5K) = 1.2mA] and External balancing current 3.6V/50 = 71.86mA. I have done the simulations for the same. The same values I have used in schematics.
Please check?
2. Temperature sensing:
Can I change the RTS_PU = 2.5K to match the threshold values to get the desired temperature.?
I would like to use 4 NTC for my application, each one per cell. Total 4 cells in series, so 4 NTC used per cell.
I understand that the threshold values are calculated based on 10K pullup and VTB =3V. I am showing the same in below
|
|
|
Min |
Typ |
Max |
|
VOTC |
Threshold for 50°C based on a 10k pullup and 103AT thermistor |
29.15% |
29.38% |
31.45% |
|
|
Condition VTB =3V |
0.8745 |
0.8814 |
0.9435 |
|
|
|
Min |
Typ |
Max |
|
VOTD |
Threshold for 65°C based on a 10k pullup and 103AT thermistor |
19.69% |
20.56% |
21.86% |
|
|
Condition VTB =3V |
0.5907 |
0.6168 |
0.6558 |
I have changed the RTS_PU = 2.5K, with this I can able to meet the threshold values for Charge 50 °C for Discharge ~60°C.
3. Change in RVDD resistor value. I would like to change the RVDD resistor value to 2K to limit the current. This is required for Intrinsic safe circuit calculations.
Can I change the RVDD to 2K?
I would be great help, if you can review the complete schematics and provide feedback.
I am attaching the schematics.
Thank you,
Regards,
-Ravi.7444.BMS review_TI.pdf
