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Bafang Ultra Drive programming

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    Also I note that the Throttle page contains:

    Start Voltage (x100mV)
    End Voltage (x100mv)

    And that Michael's page says to find the lowest Voltage the throttle will handle without errors and measure the highest voltage output from the throttle when pressed to max. Now, again, if this were just a switch then there would be no need to find both values.

    And yes, Throttle also has Start Current%, presumable with max already hard-coded at 100%, modulo Speed Limit or Designated Assist level. It seems apparent that the throttle voltage output changes as you apply the throttle and that's how the throttle is not an On/Off switch, but an analog power ramping control. How that output voltage is interpreted by the controller into what is fed into the motor is not known, but I suspect the voltage output by the throttle is converted into some Percentage based on where it is relative to Start Voltage and End Voltage, and that Percentage is used to modulate the power (probably Via applied current and probably scaled between Start Current and Limited Current (Amps) as set on the Basic Tab.

    So, it would therefore make logical sense that the Delta Voltage table output is used in a similar manner, and then the Spd table output is used to modulate that.
    Last edited by smorgasbord; 1 week ago.


    • AZguy
      AZguy commented
      Editing a comment
      The start current is the amount of power applied when the throttle is initially "cracked" so putting it at 100% would turn it into an on/off switch if the mode is current (not a fun one in a low gear for sure!)

      Most "factory" tunes I've come across have it at 10% which I find too abrupt and most folks I know turn it down. I set mine at 1% (mode current) and really like the very smooth delivery like that

    • stts
      stts commented
      Editing a comment
      waste of time
      Last edited by stts; 1 day ago.

    Originally posted by stts View Post
    But you probably don't want to chose Delta numbers that add up to the Max Voltage or you will not get the max assist until you peddle with all your might.
    You just confirmed my point, which is that no matter what you specify in the Torque Tab's Spd table, you won't achieve maximum power unless you are also pressing down hard enough on the pedal to have the Delta Table return close to the maximum output voltage.

    Michael's Torque settings kind of compensate for this, somewhat. He has 900mV in for the 0-5Kg range, 500mV for the 5-10Kg, and 300 for the 10-15Kg range. That means with only 25% of the Ultra's torque measuring range applied, he's already at 67% of the possible output! So when he goes and specifies in Spd100 that 15Kg of torque applied will produce full current, he's actually at most getting only about 67% of full power - but that's way better than a linear Delta Table would be (24%). The downside to this is that you lose that nice pedal feel you get from a slower to rise Delta Voltage table. Indeed, in using his settings I often found that pedaling harder didn't get me faster, but downshifting so I could pedal faster, even though with less force, supplied more power. That really sucked in my experience.

    Ideally, we'd have different Delta Voltage tables - one for each SpdXX range. That way we could tune the pedal torque to motor power equations different for different pedal cadences. I know that isn't going to happen, especially now that Bafang has switched to a CANBus architecture and locked away many settings. Which means that Bosch and Yamaha will continue to make motors that can't produce as much raw power but yet still provide a strong and natural assist.

    And both stts and AZguy appear to be missing my later point, which isn't about the good or badness of Throttle settings, but the SIMILARITY of the Throttle Settings to the Torque Settings.

    It's pretty logical to equate:
    • Throttle's "Start Voltage (x100mV)" to Torque's "Base Voltage (mV)"
    • Throttle's "End Voltage (x100mV)" to Torque's Delta Voltage maximum voltage (which as agreed, is measurable)
    • Throttle's "Start Current (%) to Torque's Spd Table entries for "MinCur (%)"
    • Throttle's "Designated Assist" to whatever AssistN level the rider has chosen
    As you twist a throttle further , the voltage output increases.
    As you pedal harder, the voltage output increases.

    The mapping of twist angle to voltage is set by the throttle hardware.
    The mapping of pedal force to voltage is set by the Torque Page's Delta Voltage table.

    For throttle, the algorithm scales the current fed to the motor.
    For pedaling, the algorithm also factors in cadence, but if you look at just one Spd column at a time, the settings are very similar.

    Whether the voltages output from the Delta Table are directly used to produce power was never my point. It's that in order to get the controller to tell the motor to produce maximum power, you need to have a situation such that the torque applied to the pedals is high enough to produce the maximum output of that table (which is in mV), AND you need to have SpdXX column set to produce a 100% Current. Luckily, the Ultra is so powerful that even at half power that's plenty to keep us moving well.

    But, it IS unfortunate that one has to give up pedal feel at low cadences to gain more power at high speeds. Which for me means I can tune to have a good feel for hill climbing, but then that sacrifices some power at high speed on the flats.


    • stts
      stts commented
      Editing a comment
      waste of time
      Last edited by stts; 1 day ago.