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Goin down a hill with a wheel


Zenko
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Hello all,

I'm used to go down a hill daily with my ACM 16 820wh, around 650meters  length and 65-7meters height. That gets me an average of 10% slope with variation between 0 to 20%.

Last 2 days, i got a worrisome phenomenon that happens when i go down : even with weak speed (10km/h), a little braking can be troubling. Pedals start getting tilted, and motor alarms starts bipping to death. Lucky me, I've not yet experienced a cut off at this point, but this is really annoying. I had this kind of problems with average speed 15-20km/h, and started to chill out and going slower to avoid any problem. But now, it's coming back to haunt me at low speed...

@Marty Backe i know you're the ultimate gotway user, anything to relate to this ? You probably had experienced this, no ?

I know some cases of Ninebots or small motors >800W cutting off in big slope, they couldn't sustain the effort of braking.

I'm still surprised to be so close to 80% motor power with my ACM 1500W and full battery capacity. It behaves still okay on flat ground, with hard braking and acceleration. Well, my motor axle feels a bit tired with time, will probably broke in a year or less.

I wish to discuss about some points with you buddy-wheelers, what are the recommendations and solutions to go down a hill with 100% safety ?

  • I guess the less you speed up, the less i risk to get huge W consummation spikes when i brake
  • What about taking my wheel backside ? If there's a side to drive it, maybe going in reverse could be better to brake ? Might be a stupid idea right there.
  • Bigger motor needed ? Hello Tesla, KS18L.
  • Can wheel size have influence in braking power ? Small wheel can deal with it easier ?
  • Can weight positioning on pedals influence the braking system ? I would say no, but so much physical parameters, speed, weight, slope, what's your view about this ? A little picture to illustrate the idea :
  • 59ddd91b808b1_pentewheel.thumb.png.ae2e029fe1f9620446c02a28b03c272d.png

I wish you'll come out with more advice on this, i'm a bit short on ideas right now. It's so frustrating to be going down a hill at the speed of a walker. Thanks !

PS : for those who'll come to say "just don't brake dude" => No.

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It really makes no sense that these are power warnings (aka the wheel would be close to what it maximally can do). The ACM (even the 67V you have) is a very powerful wheel, and it can go up much steeper inclines than 20% without any warning beeps, so going down 20% for a few moments should be totally ok, especially at full battery. Unless you weigh 200kg :efee8319ab:

1 hour ago, Zenko said:
  • I guess the less you speed up, the less i risk to get huge W consummation spikes when i brake

It depends on the acceleration. If you reduce your speed slowly, you need much less extra power vs. reducing the speed quickly (= hard braking). Speed isn't that important, especially when that speed is from going downhill so the wheel does not have to work for it (but at higher speeds, the wheel has less reserves for acceleration/deceleration and more energy is needed for braking/stopping, so you can't brake as hard without a cut-out like with low speeds).

1 hour ago, Zenko said:
  • What about taking my wheel backside ? If there's a side to drive it, maybe going in reverse could be better to brake ? Might be a stupid idea right there.

No difference. Electric motors work the same, no matter which way you turn them.

1 hour ago, Zenko said:
  • Bigger motor needed ? Hello Tesla, KS18L.
  • Can wheel size have influence in braking power ? Small wheel can deal with it easier ?

1500W nominal (and 3000W or so max) is more than enough! That can't be the problem (you don't weigh 200kg, right?:efee8319ab:).

What really matters is torque (which you feel when you see how quickly a wheel accelerates or brakes), not motor power. Torque is proportional to the tire radius. That means, if you double your wheel size, with the same motor power you get only half the torque for braking and accelerating (which is what you feel how "powerful" and direct the wheel reacts). So bigger tire wheels will feel more sluggish with the same motor power.

So 1500W for the 16 inch ACM is the same as 18/16*1500W = ~1700W for an 18 inch wheel. To get a wheel that feels like the ACM (and brakes and accelerates like the ACM) with a 10 inch tire, you'd only need 10/16*1500W = ~940W motor (mten3 has 800W, for comparison).

(This is only approximate, other stuff like voltage, software, etc. also decide how "powerful" a wheel feels to ride)

1 hour ago, Zenko said:
  • Can weight positioning on pedals influence the braking system ? I would say no, but so much physical parameters, speed, weight, slope, what's your view about this ?

No. If you brake with a certain deceleration, you brake with a certain deceleration, no matter how exactly you move. The motor and batteries don't care (or know).

(But how you move will make you brake faster or slower.)

--

In general, going down hills works like this:

  • Stand on the wheel, and don't accelerate or brake, just let it roll down the hill naturally (of course it will get faster and faster and faster, just like a ball rolling down a hill). This is how it behaves if it uses no power (but it gets recharged from the rotating motor).
  • If you go slower than this (you have to brake eventually, you can't go too fast), some power is needed for braking. But in the sum, the wheel still recharges because you get more power back than you need for braking.
  • If the hill is very steep or you go very slowly, and so you have to brake hard all the time, a lot of power is needed for braking, and then you don't recharge because you need more power for the braking than you get from going down the hill.
  • Also, if the wheel were to cut-out (no reason for that, but if it would), you would probably fall backwards, because without the wheel doing the braking, it would be faster, so if it's suddenly off, it would roll forwards and you fall backwards.
    So if you are braking (like going down a hill), expect to fall backwards if something happens.
Edited by meepmeepmayer
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1 hour ago, meepmeepmayer said:

I suspect what you get are overcharge warnings, not any max-power warnings. If you go down a hill, the battery recharges. If it's already full and you go down, the wheel will quickly make you stop (aka beeping and tiltback). Don't ignore overcharge warnings, even after a few meters the wheel may give up, it can happen fast!

I'm pretty sure i had the same issue with 80/90% battery. I'm well aware of overcharge warnings, and as i said, i use this road daily, since months, with full and not full battery.

49 minutes ago, meepmeepmayer said:

If the hill is very steep or you go very slowly, and so you have to brake hard all the time, a lot of power is needed for braking, and then you don't recharge because you need more power for the braking than you get from going down the hill.

I would say I'm quite in a situation like this, i need to brake all the time, basically, so if i generate a bit of a speed, and try to brake hard, bang, bip bip bip, or even worst, a cut-off. I don't feel like this is a behavior of a overcharge isn't it ? Shouldn't overcharge alarm appears when i'm just rolling down naturally ? The feeling before the alarms come when i'm trying to brake is like it starts being slippery, as if it does not want me to brake, isn't it totally against an overcharge reaction ?_?

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You can check the wheel's current with an app (Wheellog) while going down a hill. If it's high (20A or so), you're braking hard, if it's low (10A or less), you're probably recharging.

--

I can't really explain the problem. I do not even know if the 80% warning gives you tiltback or just beeps (and no idea how exactly the 80% warnings on the ACMs work, there's conflicting information and Gotway won't tell:efeee20b79:). But if the wheel gets soft, maybe that is really an overpower situation. Anyways, don't ignore the beeps, whatever the reason.

Maybe something's wrong with your wheel, especially if this suddenly appeared? Like high friction in the motor so you need way too much power - broken ball bearings, sand in there, ... no idea. Or there is a battery problem? Do you know whether you use more battery % for the same route?

For the record, what is your weight?

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8 minutes ago, meepmeepmayer said:

For the record, what is your weight?

I would said something like 90 kg stuffed on it.

Gotway 80% alarms is just a bip, never had a tilt back (at least high speed). But in a slope, i don't really know, it feel strange, like it start behaving reaaally soft. I think i heard something about an alarm for high temperatures too. That could be also an issue here. For the record :

I had trouble with my wire connection (oh hello quality), starting to melt my plastic shell, so i was worried and send back my wheel for inspection. Got my wheel back with new welding for wires, because the ACM & MS3 wires welding is crap quality (and sometimes just awful). They told me it was badly done, so resistance was producing heat at this specific point.

Too bad now, i know it's still burning up good, specially in hill climbing, but i guess it's something you can't really avoid. At least shell doesn't melt anymore, and i go easy on it for hill climbing (and i i'm not worried about a sudden cut off/ blown up wire connec

tion, it should still handle the heat). But i recently checked the inside, and feel the wires are really worn out, like they've been used for years (a bit of a dark yellow color), when it's not even 1 year.

Battery isn't a problem i think, i didn't feel any change, i'll confirm with an app review. Maybe LEDs give false information, but it's really unlikely.

20 minutes ago, meepmeepmayer said:

You can check the wheel's current with an app (Wheellog) while going down a hill. If it's high (20A or so), you're braking hard, if it's low (10A or less), you're probably recharging.

Yes sir, i'll do that !

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So your weight isn't the issue.

Temperature alarm is both beeping and tiltback. No idea what the soft/wobbly pedals exactly mean. @Marty Backe, halp!

4 minutes ago, Zenko said:

I had trouble with my wire connection (oh hello quality), starting to melt my plastic shell

Yea, have that too, my connectors did get very hot one time and started melting the side pads. Probably not much before the cable insulation would have melted then.

But sounds like you were too close to something happening too. Hills + these thin cables = :efee96588e: If you want, it would be nice if you have a photo how the inside of the wheel looks with the discolored cables etc. Your description of "worn out wires" does not sound good...

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I think the sensor is at the mosfets, not sure how much it says about the cabling. My wheel cabling (84V ACM) melted while going up a steep, looooong hill without temperature warning.

Usually, my (84V) ACM is at 47°C whatever I do. Sometimes on hills 60°C. I don't think I've ever seen more, but I usually never look.

--

I don't think it's a temperature issue though, the wobbly pedals make no sense for high temps.

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That you are experiencing tiltback in your described problem, is a 100% sign that you are experiencing a overcharge alarm, at least for me. And yes, soon after tiltbacking on a overcharge comes a cutout. 

But: Its not normal that this happens so fast(and on a battery lower than 80%), this overcharge alarm, perhaps some sensors, or capacaitors are not ok on your board.

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1 minute ago, KingSong69 said:

That you are experiencing tiltback in your described problem, is a 100% sign that you are experiencing a overcharge alarm, at least for me.

But it isn't a classic "tiltback", trying to slow me down, it's like the pedals getting soft and braking power fade out (Feel like if it try to brake more, my pedals will just be verticals without braking that much). I know my description isn't really clear...

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Just now, Zenko said:

But it isn't a classic "tiltback", trying to slow me down, it's like the pedals getting soft and braking power fade out (Feel like if it try to brake more, my pedals will just be verticals without braking that much). I know my description isn't really clear...

Yeah, on a hill down, a tiltback will feel like braking more....like from itself. 

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1 minute ago, Zenko said:

@KingSong69 but why would that happen only when i brake ? shouldn't it happen when i peak optimal speed for recovery ? like going fast at 20km/h ? It really only happens when i start braking.

I can only speak from my experience:

Because of tiltback sounds like a overcharge warning...braking gives recuperated power back, why should this only happen at a specific speed?

the 80% warning is more or less only at a fixed speed of about 36-38kmh, its no real „overpower sensed“ alarm.

But again, normally that should only happen on a full or nearly full battery...its not normal that this happens so fast, somethings fishy here.

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Might I suggest that if you have an Android phone then download and install WheelLog. Record the telemetry data from your ride. Using Excel, open the file and remove all positional data (so we can't come find you) and then post the file up here for us to look at along with the approximate ride time where the problem happened. This will help remove almost all speculation/guesses/feelings and will provides some hard data which stands the best chance of giving you and answer.

If you don't have an Android phone... well, maybe go get a cheap one (they can be had in the US from Walmart for $30 so must be available cheaply in France too) or hope that someone here can tell you how to get the same log data using DarknessBot or something similar for an iDevice.

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It's still not very clear for me from your answers :confused1:. So in terms of torque reserve margins is going downhill at 20 km/h basically the same as going 20 km/h on flat surface? But braking will be much more demanding for the motor? Overall, do I need to be very carefull when going downhill?

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I'm with @KingSong69, if you get "overcharge beeps" while the battery isn't even full, maybe the board is going bad. Or there's a cabling problem with the battery cables?

The "tiltback": I think he means that he gets no classic tiltback, but that the pedals become very wobbly (like in soft riding mode) so they react little to big inputs (big tilts). If it's really that, I don't think there is any intentional Gotway wheel behavior where the pedals go soft, is there?

1 hour ago, WARPed1701D said:

Might I suggest that if you have an Android phone then download and install WheelLog. Record the telemetry data from your ride. Using Excel, open the file and remove all positional data (so we can't come find you) and then post the file up here for us to look at along with the approximate ride time where the problem happened. This will help remove almost all speculation/guesses/feelings and will provides some hard data which stands the best chance of giving you and answer.

If you don't have an Android phone... well, maybe go get a cheap one (they can be had in the US from Walmart for $30 so must be available cheaply in France too) or hope that someone here can tell you how to get the same log data using DarknessBot or something similar for an iDevice.

Good idea!

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57 minutes ago, meepmeepmayer said:

I'm with @KingSong69, if you get "overcharge beeps" while the battery isn't even full, maybe the board is going bad. Or there's a cabling problem with the battery cables?

The "tiltback": I think he means that he gets no classic tiltback, but that the pedals become very wobbly (like in soft riding mode) so they react little to big inputs (big tilts). If it's really that, I don't think there is any intentional Gotway wheel behavior where the pedals go soft, is there?

Good idea!

I'm not aware of any Gotway behavior where the pedals act differently. I've never heard of such a thing or experienced it in the many Gotway wheels that I've owned. I can't even imagine that being a failure since pedal softness is a function of the firmware.

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I'm usually going down hill when I start out.  I never had overcharge warnings on my ACM until I upgraded my control board from the 6 mosfet to 12 mosfet board.  Then suddenly I started getting overcharge warnings on a full charge.  To avoid it I make sure to ride at a constant speed down my first hill and just avoid braking.  I imagine that you could also avoid overcharging on steeper hills by carving back and forth to slow your decent (like you would on skis or a snowboard) rather than going straight down.

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16 hours ago, meepmeepmayer said:

Usually, my (84V) ACM is at 47°C whatever I do. Sometimes on hills 60°C. I don't think I've ever seen more, but I usually never look.

My small report with wheelog -

  • Temperature - Even when i climbed last night, I didnt got more than around 41 °C. Nothing to say here.
  • Power motor - When I fully brake at around 15km/h (I didnt wanted to try much more), it doesn't use that much power, good news, I can brake hard downhill (it can't compete with acceleration consommation).
  • Current - wheelog is a mess with this, can't really make any statement, it measure upside down it seems... because it's constantly stuck around 64/67 (not sure anymore exactly). When I look into the graph, I see some huge spikes even one got to 70A, not really sure if it's possible ._. I did mess it a bit by accelerating braking hard all the way down the hill... But the high current is probably due to acceleration, not braking...

  • So... finally checking battery, starting around 91%, even when i go rather slow, it's getting near 95-96%, guess I don't really need to look somewhere else !
15 hours ago, Marty Backe said:

I agree with the general consensus - your problems are due to an extended downhill ride with full battery. People who start their rides at the top of a hill will charge their wheels to ~90% instead of 100%, and then start their ride.

I've never experienced pedal issues because of an over-charge. Only the beeping, which is called Overcharge Beeping.

Overcharge beeping is 3 short beeps followed by a 2 second pause, then 3 short beeps.

And this close the deal, thanks Marty. I remember now that distinct 3 short beeps.

What's funny is that it's been nearly a year that I climb down a hill daily to go to work, I had these annoying bips worrying me at the beginning, i just went easier on it, going slower, and never had any trouble, so I thought "damn, probably power saturation when i brake or some shit, better be cautious now."

Well, well, well... Thank you everybody ! @KingSong69@Marty Backe@meepmeepmayer@WARPed1701D

It's time for me to invest in a charge doctor, and go like a mad man on descent to not recharge too much ! I'll still continue to do some check up 

8 hours ago, oolong said:

I'm usually going down hill when I start out.  I never had overcharge warnings on my ACM until I upgraded my control board from the 6 mosfet to 12 mosfet board.  Then suddenly I started getting overcharge warnings on a full charge.  To avoid it I make sure to ride at a constant speed down my first hill and just avoid braking.  I imagine that you could also avoid overcharging on steeper hills by carving back and forth to slow your decent (like you would on skis or a snowboard) rather than going straight down.

But constant speed isn't going to charge even more battery ? so when i finally need to brake, it's gonna be even more close to a cut off ? Carving is my second life saver for it, that's for sure (I like carve-braking, I find it more efficient than straight classic brake).

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Overcharge warning starting at 91% battery? Oh well, I hope it really is this and not some board error.

3 hours ago, Zenko said:

But constant speed isn't going to charge even more battery ? so when i finally need to brake, it's gonna be even more close to a cut off ? Carving is my second life saver for it, that's for sure (I like carve-braking, I find it more efficient than straight classic brake).

As far as I know (might not be true), the faster you rotate the magnets, the more power you generate for recharging. Just an electric generator. You have that, minus the power needed for riding. So no braking and no power needed for riding (like when rolling downhills) = maximum recharging; and hard braking = lots of power used for braking and slow rotation = not much recharging. In theory, I guess. Not sure.

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Glad you made progress. If you have the log file from the ride then feel free to post it here for further analysis.

Charge Doctor is awesome so you won't regret spending the money. Just remember that every 10 or so charges to not use the Charge Doctor and leave the wheel on charge for several hours after the charger light goes green. This will allow the individual battery cells time to balance avoiding a weak link in the cell chain. On those days do not ride down the hill until you have burned some energy out the battery first to avoid this overcharge issue and potential cutout.

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45 minutes ago, meepmeepmayer said:

Overcharge warning starting at 91% battery? Oh well, I hope it really is this and not some board error.

As far as I know (might not be true), the faster you rotate the magnets, the more power you generate for recharging. Just an electric generator. You have that, minus the power needed for riding. So no braking and no power needed for riding (like when rolling downhills) = maximum recharging; and hard braking = lots of power used for braking and slow rotation = not much recharging. In theory, I guess. Not sure.

When wheel push you => power consumption

When wheel is rolling down => generate energy

So when I brake in descent, I generate energy, I get back my battery full. Therefore warning bips start coming precisely at this time.

I don't really know why, but you're theory and statement is wrong (got bashed in french forum for it). Hard braking does not generate lots of power, somehow.... A small acceleration in descent need waaay more power than a hard braking (i would say somewhere around 2 times more power needed). Also, there's a fact that energy gained from recharging might be reclaimed specifically when i brake.

Overall, I did not had overcharge warning at 91% battery in this specific situation, but the descent i take might be able to generate enough energy to make my battery full before i end the downhill, making me close to overcharging. It would not be surprising to get a full battery even with less that 90% if I roll good enough.

22 minutes ago, WARPed1701D said:

Glad you made progress. If you have the log file from the ride then feel free to post it here for further analysis.

Charge Doctor is awesome so you won't regret spending the money. Just remember that every 10 or so charges to not use the Charge Doctor and leave the wheel on charge for several hours after the charger light goes green. This will allow the individual battery cells time to balance avoiding a weak link in the cell chain. On those days do not ride down the hill until you have burned some energy out the battery first to avoid this overcharge issue and potential cutout.

Unfortunately i did it in real time and didn't activate the log file record... silly me. I'll try to do that.

I heard a lot about this balance cells thing, it didn't really meet a real consensus that it's bad to not fully charge the wheel from time to time no ? Is there more information / facts about it to confirm what you say ? Like a topic or article or review... Only fact i'm sure of is to try to keep the battery over 30% as much as possible.

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