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TIDA-010030: about the standby mode question

user6501051
Intellectual 725 points
Part Number: TIDA-010030

in page 16, what's Vload_detect, how to get this value?

in page 25, 3.2.2.4 Standby Mode

The battery pack in the first scenario should be able to detect if the charger is attached or if the battery pack is put inside of the e-bike. The battery pack in the second scenario should be able to detect if load is on or if the battery pack is plugged in outside of the e-bike.

The first pulse of PMON is to measure PACK voltage with pre-discharge MOSFET off. If the charger is attached, the voltage should be equal to 54.6 V. If not, the pre-discharge will be turned on. After a short time delay, the PACK voltage will be measured again. If the battery pack is put in the e-bike, a large capacitor will be connected between PACK+ and PACK-, therefore, the measured voltage is lower than the battery voltage. Otherwise, the PACK voltage is equal to the battery voltage.

Does the large capacitance refer to the starting capacitance of the controller? why the measured voltage is lower than the battery voltage?  but i think It takes a very short time for the capacitor to be fully charged,the  capacitor's voltage is close to battery voltage.How long is the sampling time? t=RC=302*C

Otherwise, the PACK voltage is equal to the battery voltage. The battery is placed outside the bicycle. The measured voltage is the voltage of Pack + and pack - after C71 and C70 are charged? is right?

. In the second scenario, the pre-discharge MOSFET is mostly on. If load is on, there will be a voltage drop across the resister series with the pre-discharge MOSFET, therefore, the measured voltage is lower than the battery voltage. If not, the pre-discharge will turn off. After a some time delay, the PACK voltage is measured. If the battery pack is plugged outside of the e-bike, the output capacitor is much smaller, which will cause a larger voltage drop.

i do not understand "if not"meaning? If not, the pre-discharge will turn off. After a some time delay, the PACK voltage is measured. If the battery pack is plugged outside of the e-bike, the output capacitor is much smaller, which will cause a larger voltage drop. "plugged outside of the e-bike" if the battery is outside the bicycle, because the turn off the pre-discharge, the pack voltage i think it should 0V.

  • 0
    TI__Expert 3345 points

    Hi,

    some comments as below: 

    n page 16, what's Vload_detect, how to get this value?

    Ryan: Vload_detect is a programmable value in FW, you need to configure your own value based on your system. 

    in page 25, 3.2.2.4 Standby Mode

    The battery pack in the first scenario should be able to detect if the charger is attached or if the battery pack is put inside of the e-bike. The battery pack in the second scenario should be able to detect if load is on or if the battery pack is plugged in outside of the e-bike.

    The first pulse of PMON is to measure PACK voltage with pre-discharge MOSFET off. If the charger is attached, the voltage should be equal to 54.6 V. If not, the pre-discharge will be turned on. After a short time delay, the PACK voltage will be measured again. If the battery pack is put in the e-bike, a large capacitor will be connected between PACK+ and PACK-, therefore, the measured voltage is lower than the battery voltage. Otherwise, the PACK voltage is equal to the battery voltage.

    Does the large capacitance refer to the starting capacitance of the controller? why the measured voltage is lower than the battery voltage?  but i think It takes a very short time for the capacitor to be fully charged,the  capacitor's voltage is close to battery voltage.How long is the sampling time? t=RC=302*C

    Ryan: Normally there is a huge cap on the motor control board, when there is such large cap and only pre-discharge MOSFET is on, you will see the PACK voltage will increase slowly (RC time is large because of the huge cap and pre-discharge resister), so when you MCU measure PACK voltage a short time after pre-discharge turns on, you will see smaller PACK voltage than BAT voltage. Normally the cap on the motor control board is over 1000uF.

    Otherwise, the PACK voltage is equal to the battery voltage. The battery is placed outside the bicycle. The measured voltage is the voltage of Pack + and pack - after C71 and C70 are charged? is right?

    Ryan: Right. 

    . In the second scenario, the pre-discharge MOSFET is mostly on. If load is on, there will be a voltage drop across the resister series with the pre-discharge MOSFET, therefore, the measured voltage is lower than the battery voltage. If not, the pre-discharge will turn off. After a some time delay, the PACK voltage is measured. If the battery pack is plugged outside of the e-bike, the output capacitor is much smaller, which will cause a larger voltage drop.

    i do not understand "if not"meaning? If not, the pre-discharge will turn off. After a some time delay, the PACK voltage is measured. If the battery pack is plugged outside of the e-bike, the output capacitor is much smaller, which will cause a larger voltage drop. "plugged outside of the e-bike" if the battery is outside the bicycle, because the turn off the pre-discharge, the pack voltage i think it should 0V.

    Ryan: This is a method I used to detect if battery is unattached from ebike. It uses the cap on the motor control board, before turning off pre-discharge MOSFET, MCU will detect PACK voltage to see if a load is on. "If not" means no load (PACK voltage not drop). If pre-discharge MOSFET is off and battery pack is out of ebike, the PACK voltage is almost 0V. Then MCU knows that battery is unattached from ebike.  

    Please click "This resolved my issue" if no more questions. Thanks.

    Best Regards,

    Ryan Tan

  • 0 in reply to Ryan Tan
    Intellectual 725 points
    Ryan Tan said:
    If pre-discharge MOSFET is off and battery pack is out of ebike, the PACK voltage is almost 0V. Then MCU knows that battery is unattached from ebike.  

    this is the fist step, the pre-discharge MOSFET is off, the pack voltage is 0V, if pre-discharge MOSFET is on and then OFF, the PACK voltage should be battery voltage. is right?

  • +1 in reply to user6501051
    TI__Expert 3345 points

    Hi, 

    If pre-discharge MOSFET is on, PACK is eventually equal to BAT voltage if no resistive load, and increases slowly if inside ebike. 

    If pre-discharge MOSFET is off, PACK drops quickly to 0V if out of ebike and nearly no changes if inside ebike(depends on the leakage current).

    Please click "This resolved my issue" if no more questions. Thanks.

    Best Regards,

    Ryan Tan