Chris_rider Posted January 7, 2021 Share Posted January 7, 2021 (edited) Mod edit: please see https://forum.electricunicycle.org/topic/23242-euc-world-what-does-the-safety-margin-alarm-do/ Dear euc world users Here is what I got on euc world today. Min safety margin -1%. Min battery 48% min voltage : 63.4v I'm really surprised for several reasons : 1st : I set the margin alarm to 15% and even if the transaction between phone, cardo, ear, brain can take some delay I never experienced such a low value (usually I loose 3% max). 2nd : I should have experienced cut off below 0%, shouldn't I ? And I didn't even have a tilt back. I tried to do a free spins till cut off and it literally cuts at 0% What do your guys think about it ? It's the results of hard accélération at 35kph with 60% battery left on S18.. the purpose of my post is post is mostly to understand how Tilt back/safety margin works. Base on speed and battery level or based on battery sag or amps peaks ?! Non logical fact : once at 35% battery I had Tilt back but no safety margin alert. How is that possible when yesterday I ve hit bellow 0% without even a Tilt back.. Edited September 19, 2022 by RagingGrandpa (ref more relevant thread) Quote Link to comment Share on other sites More sharing options...
Chriull Posted January 7, 2021 Share Posted January 7, 2021 (edited) Welcome! 1 hour ago, Chris_rider said: 1st : I set the margin alarm to 15% and even if the transaction between phone, cardo, ear, brain can take some delay I never experienced such a low value (usually I loose 3% max). The transition from more than enough safety margin to faceplant can be very short. For example if one rides from a flat road with 40 km/h on some steep incline one will faceplant more or less immedeately. Same is true for some "crazy" acceleration at such higher speeds. Quote 2nd : I should have experienced cut off below 0%, shouldn't I ? Negative values should not be possible. But 0% do _not_ mean cut off! Just that the wheel cannot provide anymore the _full_ needed torque - so the rider starts "rotating" forward. One could get through such overleans safely. Just if one accelerates/burdens the wheel too much this overlean comes so fast it feels like a cut off. As safety margin displayed in EUC World is 100 - inverter load. Inverter load, reported by the firmware is understood to be the duty cycle of the mosfets. From 0-100? So there is some small firmware hickup or some artefact from smoothing or wathever @Seba did to the safety margin = 100 - inverter load? Quote And I didn't even have a tilt back. Yes - tilt back comes at some fixed set speed. Not in relation with this safety margin/inverter load. So there are scenarios possible to overlean at speeds below set tiltback speed! Quote I tried to do a free spins till cut off and it literally cuts at 0% The cut off (after some beeps) at free spinning (lift cut off speed) is almost the no load speed of the motor - the maximum speed it can reach at a certain battery level. This is the only time the wheels firmware really cuts off (did not really dig deep enough into bldc control to get why this is done...) This speed could theoretically be reached going down some not too steep or too "flat" descent - but most likely one overleans the wheel before! Quote What do your guys think about it ? It's the results of hard accélération at 35kph with 60% battery left on S18.. High accelerations at high speeds necessarily lead to overleans. Quote the purpose of my post is post is mostly to understand how Tilt back/safety margin works. Base on speed and battery level or based on battery sag or amps peaks ?! Every bldc motor has a maximum torque over speed limit line. It runs between "stall torque" at 0 km/h and 0 Nm at no load speed. As written above the no load speed depends on the battery voltage. (Directly proportional) So the faster one drives, the less torque the motor can deliver. Some of this torque is needed to overcome friction, air drag, acceleration, inclines, etc. The difference to the maximum possible at the actual speed is a safety margin... For more details take a look at Quote Non logical fact : once at 35% battery I had Tilt back but no safety margin alert. How is that possible when yesterday I ve hit bellow 0% without even a Tilt back.. If one accelerates slowly on a flat road one inflicts only very low burden and can easily come up to tilt back speed. Edited January 7, 2021 by Chriull 1 Quote Link to comment Share on other sites More sharing options...
Seba Posted January 7, 2021 Share Posted January 7, 2021 1 hour ago, Chris_rider said: And I didn't even have a tilt back 1 hour ago, Chris_rider said: yesterday I ve hit bellow 0% without even a Tilt back You won't get tiltback in overlean condition, as there is no torque available to tilt you back. 6 minutes ago, Chriull said: @Seba did to the safety margin = 100 - inverter load? Yes. And if KS wheel will send inverter load as a 101, safety margin will be a negative value and this is intended behaviour. I intentionally didn't capped safety margin in 0..100 % range, to account for possible +100 % load values. Still, we don't know what exactly is that "load" value. It's possible that it's not raw PWM value as we think, but something like calculated load value, only derived from PWM. Of course there is also possibility that there was some glitch in communication or firmware operation - something that is common with Gotway wheels. CSV log would be helpful here. 1 Quote Link to comment Share on other sites More sharing options...
Chris_rider Posted January 8, 2021 Author Share Posted January 8, 2021 Thanks everyone for your replies. I guess it's a little clearer. However in my 18L I already had Tilt back at slower speeds because of hard accélération. I still think KS may have a feature built in to prevent overlean Aas long as we don't push against it. Like when it detects it may lead to overcome capabilities of the wheel it uses the remaining power to Tilt back. I'm not sure though.. Quote Link to comment Share on other sites More sharing options...
Chris_rider Posted January 8, 2021 Author Share Posted January 8, 2021 However it makes me think that Kingsong should offer a much much louder buzzer on the S18. This is. Shame after 20kmh you just can't hear it.. Quote Link to comment Share on other sites More sharing options...
Chriull Posted January 8, 2021 Share Posted January 8, 2021 3 hours ago, Chris_rider said: still think KS may have a feature built in to prevent overlean Aas long as we don't push against it. Like when it detects it may lead to overcome capabilities of the wheel it uses the remaining power to Tilt back. I'm not sure though.. They have a fixed alarm once one reaches 88% of this inverter load (12% safety margin) - 3 beeps afair. KS also has some system to reduce max speed (tilt vack speed) with battery voltage - can be seen in EUC world as red hatched part of the speed gauge. This works a bit in this direction but unfortionately nothing real is imolemented (by now). Quote Link to comment Share on other sites More sharing options...
Chris_rider Posted January 8, 2021 Author Share Posted January 8, 2021 4 hours ago, Chriull said: They have a fixed alarm once one reaches 88% of this inverter load (12% safety margin) - 3 beeps afair. KS also has some system to reduce max speed (tilt vack speed) with battery voltage - can be seen in EUC world as red hatched part of the speed gauge. This works a bit in this direction but unfortionately nothing real is imolemented (by now). Nothing imolemnted you mean about upgrading the buzzer or the Tilt back system? Quote Link to comment Share on other sites More sharing options...
Chriull Posted January 8, 2021 Share Posted January 8, 2021 1 hour ago, Chris_rider said: Nothing imolemnted you mean about upgrading the buzzer or the Tilt back system? The firmware. Upgrading the buzzer to some adaptive ambient loudness system could be great, too! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.