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Power beeps while power breaking


Scatcat
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I noted today when breaking really hard, that I got the 80% power beeps from a fully charged EUC.

As I've had two instances when the 80% power warnings have led to tilt-backs, I wonder if that could happen while breaking? I really hope it can't...

@Yi Chen or @陈小杰 is it possible to get a tilt-back (tilt-forward?) while breaking? If so, I would suggest changes in firm-ware.

If you're breaking hard enough for the alarm to trigger, you're doing it for a reason. In my case it was a BMW-driver that came into a roundabout about 15mph faster than legal, almost moving me down in the process. Only fast reactions and power-breaking put me behind him rather than under him...

I suppose it isn't an issue, just checking.

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On the KS-14C I have gotten that beep and tiltback on a really steep hill about a block away from my house. If I do a completely full charge and then ride down that hill I can get it reliably. It's really spooky. Usually I use the Charge Doctor so I'm not at full charge. 

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Braking hard on full battery is asking for trouble due to the regenerative braking (charge back to the battery has nowhere to go, thus BMS can/will kick in to protect from damaging the battery).

Never charge to full if you anticipate immediate braking situations, such as constant initial downhill.

Edited by houseofjob
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14 minutes ago, houseofjob said:

Braking hard on full battery is asking for trouble due to the regenerative braking

 

1 hour ago, Scatcat said:

I noted today when breaking really hard, that I got the 80% power beeps from a fully charged EUC.

As I've had two instances when the 80% power warnings have led to tilt-backs, I wonder if that could happen while breaking? I really hope it can't...

@houseofjob is spot on, the only faceplant I have ever had was braking after having ridden a mile or so from a full charge. My KS-14C just went limp on me and I went flying. At least your wheel warns you. Unless you need the range there is a lot to be said for using a charge doctor to stop the charge at around 85-90% and just occasionally do a full charge to make sure the cells are balanced OK.

Not at all sure it will try and tiltback but I'm fairly certain it won't tilt forward to stop you braking.

Edited by Keith
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Yup, only time I 100% charge is when I either forget, or when I need the range and know I can blast the first few miles without braking to rundown the battery and re-create that [hard] braking threshold again.

If I forget, I'm super careful in avoiding braking situations, and any braking I super gradually slowdown and/or S-curve to brake, so I don't get that full charge, regen cutout.

 

Plus, 80% charging is the BatteryUniversity-proven way to maximize lithium battery cycle life. The Charge Doctor series is invaluable IMO, as you can fine-tune cut by voltage threshold so you don't go over (I've got one for almost every wheel connection standard now!) For my GT16, I set to ~80.4V, which I believe gets me to around 80%.

Edited by houseofjob
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8 hours ago, houseofjob said:

Yup, only time I 100% charge is when I either forget, or when I need the range and know I can blast the first few miles without braking to rundown the battery and re-create that [hard] braking threshold again.

If I forget, I'm super careful in avoiding braking situations, and any braking I super gradually slowdown and/or S-curve to brake, so I don't get that full charge, regen cutout.

 

Plus, 80% charging is the BatteryUniversity-proven way to maximize lithium battery cycle life. The Charge Doctor series is invaluable IMO, as you can fine-tune cut by voltage threshold so you don't go over (I've got one for almost every wheel connection standard now!) For my GT16, I set to ~80.4V, which I believe gets me to around 80%.

Well, I do hope the next gen of RW has 1300+ Wh power, then I'd happily stop at 80%. I often start out my rides going uphill for a bit, so I loose a volt or two in the first couple of miles. I used the app to see what the numbers look like when I get over the top and start out going down, just to make sure I'm not close to overcharging - and it's no problem.

Power breaking ain't regenerative, you apply power in the opposite direction which draws power, not the other way around.

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Think whatever you like, but it still is regen braking, all EUC braking is. AFAIK, the wheel is not freely spinning in the opposite direction, it's opposing the motor still spinning in the original direction.

EUC regen is surprisingly efficient. I've helped a fellow V5F+ rider recover 1%/minute via rope-tow where I speed while the V5F+ hard brakes.

Edited by houseofjob
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6 minutes ago, houseofjob said:

Think whatever you like, but it still is regen braking, all EUC braking is. AFAIK, your wheel is not freely spinning in the opposite direction, it's opposing the motor still spinning in the original direction.

Oh, I didn't say the motor doesn't create current, it does that even without breaking. And I'm not that good an electrician to swear on which direction that will take, as in: are the power requirements of applying breaking power more or less than the regenerative current from the motor. Someone with the experience and schooling should chip in on that (@esaj, is this something you could answer?).

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@houseofjob - you've had your GT16 for quite some time now.  Could you give us a long term usage report about how it's been riding it over the past months?  Likes and dislikes, points of strengths and weaknesses?  Also, how's the Dualtron Man riding been going?  :w00t2:

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I agree with @houseofjob that all regenerative braking is returning the power from the motor, but also as I encountered with a shorted MOSFET on one wheel and as @esaj mentioned if the motor is shorted it will generate breaking.This makes me think that slow braking handles energy transfer differently than just being sent back to the battery, especially when I don't see any battery power gain on decelerating very slowly on my LHOTZ, at least to what I see from the APP. (could also be I'm not decelerating properly also)

In any case, energy transfer is never 100% efficient so breaking very slowly and S riding downhill helps where possible. If not, spare some of your energy to carry your baby downhill,;) at least overcharging warnings like on the IPS i5 are getting common on EUC and that should be enough to let you decide if you want to protect the battery or save some of your time.

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At least mostly the braking seems to be the regenerative kind, and the 80% power alarm could be triggered by high current flowing in reverse (based simply on the assumption that the 80% power warning works only by measuring the amount of current flowing, not the direction). There are other types of braking, like dynamic/rheostatic (causing the current produced by the motor back-EMF to flow through some resistance, which might be resistors or the low-side mosfets partially conducting), but I doubt that is used in the wheels as there are no large braking resistors and the mosfets would likely overheat. So-called "plugging" type braking uses the battery (or other power source) by reversing it over the motor (so kind of like trying to run it in reverse), which maybe could be used in (some) wheels. The problem with that one is that it heats up the motor windings a lot, as that's where the power of the motor back-EMF + power applied from the battery/power source is wasted and could even melt/burn them if applied for a bit longer while.

So far, I don't think anyone has shown any conclusive proof that wheels do have plugging-type braking, I think the assumption is mostly based on some app logs, where it at least sometimes seems that the speed is dropping while the current is actually running from battery to motor. But that could also just be a misconclusion, like actually riding up a hill, where the motor is using power, but the speed drops because not enough torque to keep constant speed/accelerate is provided... it's all guesswork ;) The manufacturers/firmware programmers probably know, but I doubt they're willing to share their code or intimate details about the motor drives.

Edited by esaj
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16 hours ago, Scatcat said:

Power breaking ain't regenerative, you apply power in the opposite direction which draws power, not the other way around.

This is something of a myth that got started a while ago, not helped by graphs that do not appear to have + and - signs.

this is simple conservation of energy, if you were putting energy into the wheel and at the same time the wheel is trying to dissipate energy to slow down, where the hell do you think that energy is going. With brakes you burn that energy off as heat - a lot of heat. If you consumed power to remove energy from the system that is even more energy that has to go somewhere and the only place you have got is the MOSFET heat sinks - they ain't big enough to absorb that kind of heat, however the battery, unless full, is and that is where it goes.

Edited by Keith
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This weekends leisure time problem seems not to be. This is what I got in the mail today:

gorgeous.thumb.jpg.9e6d3a7a0d95d029fe4a4d7e71601051.jpg

My old shell was pretty banged up, so I'm practically drooooooling... :D

That gorgeous blue color, somewhere between metallic and satin. A real head-turner.

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On 31/08/2017 at 9:55 AM, Keith said:

This is something of a myth that got started a while ago, not helped by graphs that do not appear to have + and - signs.

The graphs and data I have seen, e.g. this, definitely support this "myth". True, current readings have no sign, so we also don't know in which direction the wheel moves in the first place from the current readings. But, I am pretty sure that I remember correctly the following points

  • I have consistently seen the immediate voltage increase under regen braking and an immediate voltage drop under power braking (there we have the sign, in the voltage change).
  • I have seen in current graphs and (consistently) felt the switch from regen into power braking when I increase the deceleration demand during braking.
  • The observed large currents under heavy braking tend to suggest that they cannot be charge currents.
  • A forum member posted personal communications with an employee (can't remember the brand though) who claimed to know that power braking is coded in the controler.

Finally, the power warning observed by @Scatcat (if I understand correctly) is another piece in the puzzle.

On 31/08/2017 at 9:55 AM, Keith said:

this is simple conservation of energy, if you were putting energy into the wheel and at the same time the wheel is trying to dissipate energy to slow down, where the hell do you think that energy is going

The same question arises when you push with the wheel against a wall without actually accelerating. The energy drawn from the battery must go somewhere. I assume it heats up material, in particular the motor. The last time I computed this, the order of magnitude seemed to be consistent (I don't remember the numbers, but like you need to heat up the motor wires by 5-10 K for a single brake would make some sense). My observation is also that I cannot do too many power brakes in a row in a very short period of time. And the final one (last and least), the braking on my IPS is much weaker than on my two other wheels, which I suspect is due to the lack of power braking (it's a very old model). 

Edited by Mono
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There's some interesting background info on plugging-type here (if the wheels actually use battery power for braking, my best guess is that plugging would be used):

https://electronics.stackexchange.com/questions/264252/non-regenerative-braking-on-a-pmsm-bldc-motor

For those who don't want to read it: basically it says that (at least in most cases) the majority of the energy is burned off as heat in the motor windings.

Edited by esaj
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On 9/1/2017 at 11:53 AM, esaj said:

For those who don't want to read it: basically it says that (at least in most cases) the majority of the energy is burned off as heat in the motor windings.

Informative article! I find myself having to look up some of the unexplained acronyms.  The article discusses a method for fast deceleration from high speed without regeneration where they shorted the low-side of the MOSFETs for a period of time. Then they mentioned the unfortunate side-effect.... an uncontrolled deceleration. 

Has anyone considered experimenting with a mechanical brake that could be activated by simply squeezing a built in padded linkage between both calves?

Edited by Rehab1
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21 hours ago, Rehab1 said:

Has anyone considered experimenting with a mechanical brake that could be activated by simply squeezing a built in padded linkage between both calves?

If you brake the EUC under you mechanically or otherwise you will faceplant. A mechanical brake activated by the controller is an option, if backwards out-leaning the wheel is actually a problem.

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1 hour ago, Mono said:

If you brake the EUC under you mechanically or otherwise you will faceplant. A mechanical brake activated by the controller is an option, if backwards out-leaning the wheel is actually a problem.

Your correct! It would require an electronic braking system simlilar to one incorporated in the new Uno Bolt. http://www.unobolt.com/

I wish there were more details on how Sean Chen, the inventor, integrated the electronic brakes into the regenerative brakes on the BLDC motor.

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  • 1 month later...
On 30/8/2017 at 9:54 PM, houseofjob said:

Già, solo il tempo che ricarico al 100% è quando dimentico, o quando ho bisogno della gamma e so di poter esplodere le prime miglia senza frenare per abbattere la batteria e ricreare di nuovo quella soglia di frenata.

Se dimentico, sono super prudente nell'evitare situazioni di frenata e qualsiasi frenata di super-graduale rallentamento e / o curva di S per frenare, quindi non ottengo quella carica completa, regen ritagli.

 

Inoltre, il caricamento dell'80% è il modo dimostrato da BatteryUniversity per massimizzare la vita del ciclo della batteria al litio. La serie Charge Doctor è IMO prezioso, in quanto è possibile ottimizzare il taglio dalla soglia di tensione in modo da non andare oltre (ho uno per quasi tutti i standard di connessione a ruota!). Per la mia GT16, ho impostato a ~ 80.4V , che credo mi porta a circa l'80%.

Come si fa a impostare? 

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1 minute ago, Francesco Gulberti said:

Come si fa a impostare? 

Buy the correct Charge Doctor for your wheel (buy direct from hobbyist (France), the maker, here), ...

... then use in dn A (ampere-based) mode for ~320wh wheels or below; or for larger/all batteries, use in up V (voltage-based) mode.

For down A mode, setting 1A usually corresponds to around 90% charge, adjust accordingly.

For up V mode, setting ~80.5V for 84.4V wheels or guess-timating ~64V for 67.7V wheels will get you in the ballpark for 80% charging cutoff.

 

See @hobby16 / hobbyist's site for full details.

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