Full battery down hill??

[supercurio]

3 minutes ago, Tawpie said:

An EUCWorld tour recording should be quite helpful...

Seconding that! Seeing the battery Voltage rise with the current drawn going negative will leave no doubt.

Edited March 22, 2022 by supercurio

[techyiam]

Me three. Not just because it is annoying to the OP, but because the warning message "please repair" is worrisome to me. Doesn't inMotion warning message "please repair " means the owner needs to take wheel in to get it checked out?

[meepmeepmayer]

1 hour ago, LandoCycle said:

I'm aware the board needs to dissipate the power into heat if the batteries are fully-charged.

The board can't do that. The motor generates power downhill, and it either goes in the battery until the battery is overcharged enough to fail (catch fire), or the wheel stops (warning, and if you ignore it, sudden emergency shutdown) before that. There is no extra heat dissipation mechanism. It's "stop or fry".

1 hour ago, LandoCycle said:

The odd thing is that NONE of my other wheels are bothered, just the V11.

The V11 might be more finicky/careful with overcharging. Or it is better in regenerationg energy when going downhill. Or your V11 charger is better (stops at a slightly higher voltage) than your other chargers.

7 minutes ago, techyiam said:

If it is overcharging or over-voltage, why it is OK for the lighter rider?

Both kinetic energy (movement) and potential energy (lift energy) are proportional to weight. When you brake and go downhill, you get a percentage of that energy back, so higher weight means more regenerative charging. Eventually every rider will get a full battery going downhill, but for lighter riders will take longer, and they might run out of hill first.

14 minutes ago, techyiam said:

Also, the "please repair " warning message is worrisome. 

Yes, that's the confusing part. But presumably overvoltage is seen as generic error. I thought IM wheels had specific overcharge voices, but maybe not?

[techyiam]

21 minutes ago, Tawpie said:

It must be on the edge of over voltage... the higher mass of the heavier rider has more potential energy at the top of the hill than does the lighter rider. A (small) amount of that energy is converted to regen power but I suspect that because the lighter rider has less potential energy, they're actually power neutral or slightly using power on the way down.

 

10 minutes ago, meepmeepmayer said:

Both kinetic energy (movement) and potential energy (lift energy) are proportional to weight. When you brake and go downhill, you get a percentage of that energy back, so higher weight means more regenerative charging. Eventually every rider will get a full battery going downhill, but for lighter riders will take longer, and they might run out of hill first.

Thank you for the explanations. Just wondering, hypothetically speaking, if a rider can stay upright but stationary on a steep hill, is there any regen? No right? For regeneration, the wheel has to drive the motor, not the other way around. And the wheel has to rotate fast enough.

[techyiam]

2 hours ago, LandoCycle said:

Every time I try it on the V11 I get tilt-back and a "please repair" voice

When you ride down the hill faster, does the tilt-back occur further down the hill? My thinking is that the wheel is now "driving" the motor less, and hence less regen. If the tilt-back occur at about the same distance down, regardless of speed, then it will even more puzzling. 

Edited March 23, 2022 by techyiam

[meepmeepmayer]

24 minutes ago, techyiam said:

Just wondering, hypothetically speaking, if a rider can stay upright but stationary on a steep hill, is there any regen? No right?

Yep, then just nothing happens.

You can imagine shorting the motor, which locks it in place and acts as a parking brake. That itself doesn't need energy, and works without a battery (any fried wheel with the battery removed and the motor cables involuntarily connected will have the tire locked in place). And of course it also cannot magically create power from nothing.

24 minutes ago, techyiam said:

For regeneration, the wheel has to drive the motor, not the other way around. And the wheel has to rotate fast enough.

I think it works this way: when you accelerate, power goes from the battery to the motor. Whenever you brake (decelerate), the motor generates power that goes into the battery. So any braking recharges your battery.

Rolling down a hill, you would normally get faster and faster, but in reality you keep a certain speed, so in effect you are constantly braking. And braking means regen.

14 minutes ago, techyiam said:

When you ride down the hill faster, does tilt-back occur further down the hill?

From my experience, going down really slowly creates the most regen (or at least the most heat). Not sure why. Maybe it is the lack of air resistance? If it is, not sure it makes enough of a difference to notice how far you can go down before the warning. I wouldn't try it. Or at most very carefully.

Edited March 23, 2022 by meepmeepmayer

[techyiam]

10 minutes ago, meepmeepmayer said:

From my experience, going down really slowly creates the most regen (or at least the most heat). Not sure why. Maybe it is the lack of air resistance. Maybe some other reason.

If I am not mistaken, on descend at a really slow speed, the steeper the hill, or the slower you go, or the heavier the rider is, more heat would be generated because the motor has to worker harder to power the wheel in reverse?

[meepmeepmayer]

1 minute ago, techyiam said:

If I am not mistaken, on descend at a really slow speed, the steeper the hill, or the slower you go, or the heavier the rider is, more heat would be generated because the motor has to worker harder to power the wheel in reverse?

Imagine starting on a hill at a certain speed, and going down the hill and then stopping. Your kinetic and potential energy from that goes into regen (and motor heat). In principle, the way you do it shouldn't matter. So (in this simple theory) speed shouldn't matter (ignoring air resistance where speed certainly matters), and steepness shouldn't matter as long as the overall height difference stays the same.

There might very well be different regen efficiencies at different speeds (and temperatures) or when braking harder.

Or the motor might just do something entirely different at very low speeds (close to standstill) where it doesn't regen and just fine-balances. I think @RagingGrandpamentioned something like that once.

I don't know. Maybe my wheel just got hotter due to the lack of cooling from the wind when going really slowly.

[Richardo]

I recently read something about how, due to the way electronic braking works, most electric motors can't do it at very slow speeds, and they're actually programmed to put energy into the motor to do low speed electric braking. 

I don't understand how that could work, because if you short the mosfets the wheel sure does apply the brakes! Maybe that 'fact' only applies to certain applications? (Maybe this was in the thread about switching escooters to full electric braking)

[meepmeepmayer]

1 minute ago, Richardo said:

I recently read something about how, due to the way electronic braking works, most electric motors can't do it at very slow speeds, and they're actually programmed to put energy into the motor to do low speed electric braking. 

Yes I remember that too. Well said. No idea about the details.

[OldFartRides]

I’ve wondered about this when doing slow lazy s’s down steep hills. I “felt” like it should require energy to hold me back.

[mrelwood]

Whenever the motor is rotating, it creates voltage. It will recharge the battery only when this regenerating voltage is higher than the opposing motor driving voltage. On a shallow decline the energy required to overcome the wind and ground resistances can be larger than what a careful braking will produce. Hence, the battery voltage doesn’t increase.

 If you make the decline steeper or brake harder or reduce the wind resistance, at some point the regenerated voltage gets higher than what the controller provides for balancing, and the battery gets charged. How steep and how fast this happens at is anyone’s guess, and depends on many factors.

 The V11 has indeed just a few warnings that are used for a myriad of situations. “Please repair” is a generic warning for overvoltage, undervoltage, battery pack voltage difference, mainboard issues etc. In this case it’s of course about overvoltage.

 

8 hours ago, meepmeepmayer said:

You can imagine shorting the motor, which locks it in place and acts as a parking brake.

Not a very strong one though. Even when a mosfet shortcuts the motor, while it provides additional resistance it can still be rotated easily by hand.

 

8 hours ago, meepmeepmayer said:

From my experience, going down really slowly creates the most regen (or at least the most heat). Not sure why.

Heat doesn’t come only from the regenerated energy. At slow speeds the section width of the PWM signal is wider, so there is more DC current applied to the motor. DC heats the system pretty effectively, and isn’t related to regenerating but to the riding speed only. We all know the wheels heat up very nicely on slow inclines as well.

[Chriull]

8 hours ago, Richardo said:

I recently read something about how, due to the way electronic braking works, most electric motors can't do it at very slow speeds, and they're actually programmed to put energy into the motor to do low speed electric braking. 

Yes. Normal regenerative breaking works with the motor plus controller performing as a boost converter as shown in figure 1 in the section circuit analysis in  https://en.m.wikipedia.org/wiki/Boost_converter

28 minutes ago, mrelwood said:

Whenever the motor is rotating, it creates voltage. It will recharge the battery only when this regenerating voltage is higher than the opposing motor driving voltage

The motor never generates a voltage higher than battery voltage if it turns below lift cut off speed.

So it has to be boosted upwards. The breaking torque can be regulated by the "boost factor".

The more the voltage is boosted up, the more inefficieny rises. And there of course has to be enough mechanical power to provide the electrical power for charging plus the losses which equals the power for braking again.

So "low" speed regenerative breaking can and does not work.

Short circuiting is a bit more effective as regenerative breaking, but still degrades with lower speeds.

Last possibility afair called ?plugged? breaking - for single phase dc motors this is achieved by simply reversing supply voltage. For our 3 phase bldc motors this means to commute the motor in a way so that the generated rotating magnetic field vector "is behind" the static magnetic field vector of the rotor (outrunner). So the rotor brakes/decelerates.

This should happen all the time during normal "constant speed" cruising as to balance us riders the wheel has to change permanetly between acceleration and deceleration. 

Or at slow and smooth pendulums braking and direction change should be quite indistinguishable - just a smooth transition.

[RagingGrandpa]

(Merged now with prior same-topic thread)

20 hours ago, LandoCycle said:

I basically live on a giant hill, and to get into town is about 500' of elevation downhill. Usually, I leave my house on full-charge and have had 0 issues on any of my other wheels (V10F, S18, 18XL, V8F). Every time I try it on the V11 I get tilt-back and a "please repair" voice

Interesting that your S18 doesn't alarm, and your V11 does. They're the same voltage, and the S18 pack is smaller.
Seems to me that the Inmo overvoltage alarm threshold is simply "tighter" than the S18's threshold.

Full-charge to ensure cell balancing. Don't partial-charge.

Sounds like you should plan on doing some climbing or pendulum-ing, if you need to descend immediately after charging.

 

Edited March 23, 2022 by RagingGrandpa

[alcatraz]

It would be cool if there was a way to charge to 100% and then bleed off 5%, with the charger. Add a discharge program to it.

[mrelwood]

On 3/24/2022 at 1:25 AM, alcatraz said:

It would be cool if there was a way to charge to 100% and then bleed off 5%, with the charger. Add a discharge program to it.

After charging, power on the wheel and set the headlight to 100% brightness. It’s only a 18W light, but half an hour like that is still something. Could be just enough.

[LandoCycle]

Ok guys, more info:

I just picked up another V11, this one is second-hand with about 2,200km and is an older batch. I DO NOT have any problems with it going down the same hill. So now I'm starting to wonder if the new V11 does have a small battery calibration issue.

[meepmeepmayer]

I'm not sure what a "battery calibration" issue would even be. And I don't see any problem in this situation overall, but it's always good to be curious, who knows what one might learn.

Do both V11 have the same firmware? Maybe the BMS (firmware) is different between them? Maybe the battery is just older and doesn't charge to the same voltage the newer one does, so the regen doesn't reach the overcharge warning? Do you use the same charger for both of them?

 

[LandoCycle]

6 minutes ago, meepmeepmayer said:

I'm not sure what a "battery calibration" issue would even be. And I don't see any problem in this situation overall, but it's always good to be curious, who knows what one might learn.

Do both V11 have the same firmware? Maybe the BMS (firmware) is different between them? Maybe the battery is just older and doesn't charge to the same voltage the newer one does, so the regen doesn't reach the overcharge warning? Do you use the same charger for both of them?

 

Yeah, I thought that maybe it was battery degradation causing it. They're both up to date on the latest firmware. 

[mrelwood]

13 hours ago, LandoCycle said:

Ok guys, more info:

I just picked up another V11, this one is second-hand with about 2,200km and is an older batch. I DO NOT have any problems with it going down the same hill. So now I'm starting to wonder if the new V11 does have a small battery calibration issue.

Each V11 has a calibration setting for the voltage reading. It is perfectly normal that the calibration of the measurement varies between units.

 Check the wheel voltages after a charge. Do you see the same values on both wheels?

[Grimm10]

Move to the bottom of the hill.  Problem solved. 😄