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Unexpected result from small changes

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    AZguy
    Giga Member

  • AZguy
    replied
    The parameters are much further removed from the actual motor control - think of them more as an abstraction layer... I don't think you can exceed the performance possible from the motor - you certainly can exceed some batteries ability to deliver the power requested but that's an entirely different thing and would most likely just trip the LVCO. E.g. the current settings are the battery current and have pretty much have almost nothing to do with the actual motor current...

    Outside the PAS current/speed settings which I may change up as though they are one parameter, when I tune, I rarely change more than one parameter at a time though

    FWIW I typically run 100% speed like you have across PAS 1-9 and set the keep current at 90% which seems to keep the speed of the bike from being much of a factor outside how much power it takes to maintain that speed - not so sure I'd go to 100%. I don't much care for a linear PAS current (motor power) progression but it's common - I go for a geometric progression but that's a different topic. My current decay is also presently set at 8. My start current is much lower and I've run it in the 6-10% range and I understand you can run into problems if it's set too high....

    I ride plenty off road and lower gears too - about 7000mi on this unit... I have no issues like you are describing with any of the batteries I've run

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  • K442
    replied
    Unfortunately, I'm sort of 'locked in' to the programming on my X1 and have never had a BBSXX to experiment with, but slow day here, so thought I'd offer my .02

    What you describe - small changes have big effect (especially in a downward / power loss direction) - doesn't seem to be too unexpected. Your motor is trying to build a rotating magnetic field to keep the rotor spinning with the speed and torque you want at any given time. It has to do this within the voltage and current parameters available from the battery, deliverable through the controller and within the physics that the motor is subject to. (weight of bike & rider, wind resistance, gear ratio, etc)

    This is a bit like juggling where you can adjust the direction and speed you throw a ball, but ultimately the balls are subject to gravity and wind resistance. In 'normal' conditions, you can likely make small changes and have a slight + or - effect. But near a boundary condition (ie the balls only fall out of the air so fast), a small change in how fast you throw can mean the ball misses your hand on the next cycle and suddenly all the balls fall out of the air.

    Going back to your motor, if you made more aggressive settings and actually got less power, it likely means you've exceeded the performance possible from the motor. But the extra power you're throwing at it is going somewhere! Likely excess amperage in the windings or high voltage spikes in the controller. So probably best to tune back to a normal operating range...at least until you can identify what specific parameter is causing the problem and adjust accordingly

    Thus concludes my .02 cents worth of free advice with no experience to back it up! lol

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  • dward05
    started a topic Unexpected result from small changes

    Unexpected result from small changes

    I have a BBSHD installed on a full suspension mtb . Totally impressed with how the bike rips. But my only small complaint is that the power drops a little bit at high pedal cadence, really notice it in lowest gears goin up hills. I made a couple small changes hoping to fix it so the power output would be constant no matter what the pedal cadence is.

    I changed,
    PAS Levels 1 - 9 only very slightly,
    KEEP CURRENT from 80 to 100
    CURRENT DECAY from 4 to 8
    START CURRENT from 20 to 30

    Those changes didn’t help, it just restricted the hell out of the motor. Where usually I’d ride in PAS1 2 and 3, I had to use PAS 6,7,and 8. It was so drastic I thought maybe I accidentally lowered the max current down to 15 Amps or so. Was not the case though. Very strange
    Last edited by dward05; 01-29-2021, 08:23 AM.
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