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Observation going uphill.


LanghamP
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Going uphill uses a tremendous amount of energy, but not all at once. I have some steep and long hills around where I live, and jog, bicycle, and EUC up and down them.

My biggest observation is that if you go up them on an EUC about as fast as you could trot up them without breathing hard then you'll be just fine on your EUC regardless of your weight.

Edited by LanghamP
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That's only 50% true, from my (very little) experience looking at numbers while going uphill.

In the end, you lift something which is the biggest part of the energy you need to provide, and if you lift it faster (speed is proportional to height lifted) you need more power aka a higher current.

But there is a "good zone" between very slow and fast where your current depends very little on speed. But that zone is not that big, and going faster then will give you a higher current (as will going very slow).

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31 minutes ago, meepmeepmayer said:

if you lift it faster (speed is proportional to height lifted) you need more power aka a higher current.

True, but that power is mechanical power, and the current(no matter which) is dependent on the efficiency of the motor which in turn depends very much on the speed. The current I'm referred to is the motor current.

Edited by zlymex
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This is interesting because i've read some posts saying going uphill overtaxed their machine and caused cut-outs, and so did transitioning from a flatter to a steeper incline.  I confess that made me nervous about the idea of going up hills quickly.  But I think that if I'm going to be safe doing that on any machine, my new MSuper is likely to be one of the wheels most likely to handle that safely.

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12 hours ago, zlymex said:

True, but that power is mechanical power, and the current(no matter which) is dependent on the efficiency of the motor which in turn depends very much on the speed. The current I'm referred to is the motor current.

efficiency is however in favour of higher speeds. 

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I mean to clarify that climbing up hills using the same forward pressure you use on level ground uses the same wattage. The wheel will slow down going uphill, sometimes by a lot, but as long as the wattage stays the same then everything is ok including overheating problems.

I think.

I weigh 215, haven't had problems overheating yet on my KS14C. Some hills are absurd, I have problems even just walking up them, but my EUC is just fine.

Amazing devices.

Edited by LanghamP
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2 hours ago, LanghamP said:

The wheel will slow down going uphill, sometimes by a lot, but as long as the wattage stays the same then everything is ok including overheating problems.

You can easily see why this is probably not the case by looking at the limit when speed goes to zero. At zero speed, all the wattage as to be converted to heat, because kinetic and potential energy remain the same.

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On 7/8/2017 at 4:08 PM, Mono said:

You can easily see why this is probably not the case by looking at the limit when speed goes to zero. At zero speed, all the wattage as to be converted to heat, because kinetic and potential energy remain the same.

I can't figure this one out. I have been looking at my wattage on my KS14c and my MSuper V3s, and the trend seems clear; the faster I go up a hill (not accelerating but staying at the same speed) the more wattage I use.

However...

I did get my KS14c to overheat twice. I started at the bottom of the hill at the same temperature, I went up the same hill using the exact same path.

--Going uphill quite slow (~6 mph), I used less wattage but the wheel overheated and kicked me off about halfway up.

--Going uphill much faster (~10 mph) used up more wattage BUT the wheel overheated and kicked me off at nearly to the top.

I will say going uphill at higher speed is scary as hell, and that is where my 100kg makes that a pretty bad idea. The wheel kept skipping, surging, falling behind then catching up. It doesn't do that going slow.

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21 hours ago, LanghamP said:

I can't figure this one out. I have been looking at my wattage on my KS14c and my MSuper V3s, and the trend seems clear; the faster I go up a hill (not accelerating but staying at the same speed) the more wattage I use.

That's an easy one: The faster one goes up the same incline, the more power (wattage) is needed ( P potential = m * g *  h * delta h / delta t ...with delta h / delta v = the vertical speed ). But the same Energy is needed, since one is faster on top with the higher speed - so E potential = m * g * h is not dependend on speed or time anymore.

(Edit: Or the other way round E = m * g * h and P = delta E / delta t = m*g*delta h / delta t)

You see the wattage from a wheellog/9BMetrics/the app?

However - they report the wattage wrong (the slower one goes the bigger the difference)! Most wheels report the motor current and the battery voltage and multiply both for the wattage.

But since Battery Voltage and Motor Voltage are different (the PWM signal is used to lower the battery voltage to the needed motor voltage, which is dependend mainly on the speed) and with Power Battery = Voltage Battery * Current Battery = Power Motor (+ Losses) = Voltage Motor * Current Motor (+ Losses)  the motor current is higher than the battery current (the lower the speed -> the lower the motor voltage -> the higher the motor current!)

So the lower the speed the bigger the error of the wattage the app shows (it shows always too much).

Quote

However...

I did get my KS14c to overheat twice. I started at the bottom of the hill at the same temperature, I went up the same hill using the exact same path.

--Going uphill quite slow (~6 mph), I used less wattage but the wheel overheated and kicked me off about halfway up.

--Going uphill much faster (~10 mph) used up more wattage BUT the wheel overheated and kicked me off at nearly to the top.

I will say going uphill at higher speed is scary as hell, and that is where my 100kg makes that a pretty bad idea. The wheel kept skipping, surging, falling behind then catching up. It doesn't do that going slow.

So you went up the first time the hill up with v  which needed a power of p for t seconds.

The second ride was with 1.6 * v, so you needed a power of 1.6 * p for 1/1.6 * t seconds.

But with the higher speed you had a relatively lower current  - and the mosfet and ?some? motor losses are ~proportional to the square of the motor current.

So presumably riding at 1.6 * v with a power of 1.6 * p needs in your example a comparable motor current as going up the hill with v and a power of p - but since you were faster the second time you came further...

 

Edited by Chriull
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