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Bafang Ultra Drive programming

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  • stts
    commented on 's reply
    waste of time
    Last edited by stts; 1 day ago.

  • smorgasbord
    replied
    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.


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  • stts
    commented on 's reply
    waste of time
    Last edited by stts; 1 day ago.

  • stts
    commented on 's reply
    waste of time
    Last edited by stts; 1 day ago.

  • AZguy
    commented on 's reply
    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

  • smorgasbord
    replied
    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.

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  • smorgasbord
    replied
    The Torque sensor is a switch. The motor can't run till the switch is turned on. But the switch is not connected to the Motor. The switch is connected to the software. The switch is connected to Delta table. So if there is no Delta table, then the software can never turn the motor on. So we have the Delta table. with not one, but 8 different switches. And the SPD table looks at the Delta table to see if any switch is turned on. If it is, the software looks at the speed to see which SPD to turn on.
    From what you're describing, the Delta table will ALWAYS return ON if we've set our Base Voltage correctly and there's ANY pressure on the pedal.

    I think you're trying to say that ALL the torque scaling is derived from the Spd table, where it looks at applied Torque relative to START and FULL, and then scales Current to be the same relative amount between MinCur and MaxCur. But, if that were true, then what's the point of different values in the Delta Table? As long as applied Torque is above Base Voltage, won't the Delta Table "Switch" be ON?

    And if so, what's the purpose of the 8 other entries in the Delta Table, and why are they scaled voltages instead of just ON/OFF (1/0) values?

    Remember, the Spd Table doesn't reference anything in mV, so how is it connected to the Delta Table?

    I definitely felt a change in power output when I changed values in the Delta Table. The Michael/Frey values (900 for 0-5Kg, 500 for 5-10Kg) made the motor Power go up too quickly and then flatten out. They weren't just on/off switches for power. Same Spd table values, but different power outputs at different pedal pressures.



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  • stts
    replied
    waste of time
    Last edited by stts; 1 day ago.

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  • stts
    replied
    waste of time
    Last edited by stts; 1 day ago.

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  • smorgasbord
    replied
    Originally posted by stts View Post
    Heres another manual,
    The Bafand Ultra is here. You might not know it by looking at it, but this 48V mid-drive is packing 1,500W peak of power at 160Nm of torque, more than any other PAS e-bike motor on the market. Here we look at it in detail.


    It has much better details of very important PAS screen parameters. They have to have an impact unless it's been disabled. So you can study each parameter and watch for a specific behavior change to verify your access. These will help make the motor perform smoothly, so hope you get results from changes. But change carefully, as you can also make the motor performance rougher.

    Now back to Torque screen and this is a much clearer manual. 0 Speed Boost time‚Äč is interesting. Used when starting on a hill. It seems to give you a kick start of a half a second when starting from zero. Good on hills it says. But people have complained of sudden kick starts in postings. So this may be a confusion factor. Something to play with for you.

    SPD chart. Oh this is an awesome bunch of parameters. I'm looking at all this and wondering why I got the motor I got. Hah.
    Well, that's the "Michael" guide I referenced earlier, that has what I think are inappropriate values for the Delta Voltage table, essentially loading it up early in the pedal torque, and then reducing as torque increases. That all seems exactly backwards of what you'd want, which is an increasing increase (exponential?) in power out as pedal torque increases. Using the settings Michael references in that "manual" gave me a ride that would run out of steam early unless you downshifted to get pedal cadence up to pop you into one of the higher Spd bands that hit MaxCur early. I'm much happier with a small variation of ProphetZarquon 's settings.

    But, still trying to understand how these settings interact. Seems pretty straightforward for PAS (and I've got a nice exponential increase happening there that feels great) and the Spd table, but I still don't get how Delta Voltage and Spd tables interact with each other, again especially since one is for voltage and one is for current.

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  • smorgasbord
    replied
    Originally posted by stts View Post
    No no no no. You got the wrong idea what that 2436 is doing. You can get any power you want based on that voltage. What your doing in the Delta chart is telling the software 8 plus 2 endpoint voltages to watch out for. That's it. That's what the Delta chart is for. Its defining voltages that will be slightly different from motor to motor, and bike to bike.
    Sorry, I don't know what "watch out for" means. Can you explain it further?

    Originally posted by stts View Post
    And forget about Oms law. Its not going on here. The controller has a second processor running the mosfets, and its doing all the Ohms law work for you.
    Yes, I do understand that the voltage from the Delta Voltage table isn't directly used to calculate the power output, but if I put higher values in the Delta Voltage table, then won't I get more power out of the motor at lower pedal torque? And conversely, if the pedal torque is such that the calculated voltage isn't close to 3260mV then I'm not close to getting maximum power output from the motor, no matter what the Spd table or PAS level say, right?

    Why would Bafang use voltage for torque/pedal pressure and current for cadence & PAS? It can't be a coincidence that power = volts * amps.

    Maybe another tact, two quetsions:
    1) If I'm only applying 25Kg of force on the pedal, given the stock Torque Tab settings, how does that get me to maximum power in the Spd100 range, where 25kg equals 100% current?
    2) If Home above gets me to Max Power (assuming PAS level is 100), then what's the point of the Delta Voltage table at all? How does that scale the power output if the Spd table says Full(Kg) always gets you MaxCur(%) and that always gets you Max Power is PAS is 100?

    Color me confused. Again. Sorry.

    Last edited by smorgasbord; 1 week ago.

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  • smorgasbord
    replied
    Originally posted by stts View Post
    ...you will have to use the manual and alter each setting to gain the understanding of how each parameter changes your motor performance.
    Wait - you've got a manual for this? From where can I get a copy? Everything I've read is what people have determined from experimentation, not from any manuals Bafang or any OEM publishes.
    Last edited by smorgasbord; 1 week ago.

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  • stts
    replied
    waste of time
    Last edited by stts; 1 day ago.

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  • smorgasbord
    replied
    Sorry if I wasn't clear about the "limiting factors" here. Let me try again:

    To oversimplify, Power is Voltage * Current:
    • The Delta Voltage table tells the controller how to scale Voltage based on pedal pressure.
      • There's some additional flexibility in that you have 8 pressure ranges in which to specify the Voltage scaling factor.
    • The Spd table tells the controller how to scale Current based on pedal pressure.
      • There's some additional flexibility in that you have 6 cadence ranges in which to specify the Current scaling factor.
    • There's one more Current scaling control, which is the PAS "Assist Level," which servers only to limit the ultimate Current that could be produced.
    So, in order to get maximum power out of the motor, you need ALL of the following at the same time:
    • Your Delta Voltage table values plus the Base Voltage must sum up to, or exceed, the maximum possible Voltage output, which is about 3,260mV.
    • You're applying enough pedal pressure such that the Voltage sum produced reaches that 3260mV.
    • Your cadence falls into one of the SpdXX ranges (0, 20, 40, 60, 80, 100)
    • Your SpdXX MaxCur(%) is 100
    • Your SpdXX Full(Kg) value that is less than or equal to your actual pedal pressure.
    • Your Assist Level in the current PAS is 100.
    For the sake of argument, let's ignore the PAS control, or just assume it's at the highest level (100). The problem is that I can only get to full power if BOTH the Delta Voltage table AND the Spd table produce their maximums. That's Max Voltage (3260mV) for Delta Voltage AND 100% Max Current (30 amps typically non-modified Ultras) for Spd. Which means that if I set the Spd Full(Kg) to a value less than the corresponding Delta Voltage max producing entry, I won't get both unless my pedal pressure really is that high.

    Perhaps an example:
    • PAS Assist Level: 100
    • Base Voltage: 780mV
    • Delta Voltages: 207mV for the first four, 414mV for the last four. (So at 60Kg the sum is 3260mV, the typical Ultra max)
    • All SpdXX columns have:
      • Full(Kg) at 40
      • MaxCur(%) at 100
    Now, I'm pedaling with a pressure of 40Kg. Cadence doesn't matter since all SpdXX columns are the same. While I will get full current from the Spd table, I won't get Max Voltage out of the Delta Voltage table (at 40Kg I'll only get 2436mV), so I won't be getting full power.

    The only way around this would be to reach Max Voltage in the Delta Voltage table at 40Kg of pressure, but having higher than 207/414 values. That's certainly do-able, but then I get no additional benefit from the motor when I pedal harder than 40Kg. In essence, I've restricted the torque range down. And the question then is how far down does one need to go? The issue is that humans can't put 60Kg of pressure on pedals that are turning at 120 rpm (or at whatever rpm triggers Spd100), but some can at 20 or even 30 rpm. If I want maximum power climbing hills at a 30 or even 60 rpm cadence with a 60Kg pressure, I can't then get maximum power on flat ground where I'm going really fast and have a fast 100-120 rpm cadence.

    So, if we want Max Power available, we need to reduce the torque sensing range such that the top mark is achievable at the fastest cadence in which we want Max Power. I want to climb a steep hill at, say, 30 rpm cadence and have the power scale as my pedal pressure increases up to my max (say 60Kg) to achieve Max Power. But, I also want Max Power when I'm on the flats in the highest gear and pedaling at 120 rpm cadence where I can not achieve 60Kg or pedal pressure. I have to give up one or the other.

    At best, the Spd table helps you compensate SOMEWHAT with higher current values at higher cadences, but doesn't help you reach the highest voltage values you need to achieve Max Power.

    I'm thinking I need to get more familiar with the "Torque Live Data" page in my EggRider. This not only gives me the current voltage, but also a "Speed Signal Level" and "Speed Signal ACC" as well as "Level High Time" and "Level Low Time." I'm wondering if there's a way to translate that page into actual Kg of pressure and which SpdXX range I'm currently in. Anyone know?


    Last edited by smorgasbord; 1 week ago.

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  • stts
    commented on 's reply
    waste of time
    Last edited by stts; 1 day ago.
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