New Electric Bike but one small niggle

[flecc]

it would make sense to abandon the power limit and just have a speed limit.

The European Parliament made a recommendation to do just this, but sadly the EU Commission turned it down.
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[flecc]

the woosh Gallego has a new solution to comply with the new regulation, the throttle only activates after you rotate the cranks for about half a turn. Then it works like a normal throttle.

I don't think this complies though, due to there being no phase down of power with the throttle in use, as mentioned here
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[SteveRuss]

The maximum continuous power is the power at which it won't overheat. The maximum power is the most it will produce, but it will overheat, so it can only do it for a short time.

So what you are suggesting is. If you want to minimise the over heating of the motor, then rotation speed is the key? Rather than keeping it in a high gear and using all your leg power to go up a hill, you'd be better off (and the motor more to the point) if you go down a number of gears so that the motor is spinning at a more vigorous revolutionary speed?

 

[flecc]

So what you are suggesting is. If you want to minimise the over heating of the motor, then rotation speed is the key? Rather than keeping it in a high gear and using all your leg power to go up a hill, you'd be better off (and the motor more to the point) if you go down a number of gears so that the motor is spinning at a more vigorous revolutionary speed?

Overheating is more likely to be an issue with hub motors, since they include the most powerful e-bike motors. They are completely independent of the cycle gears used of course, so for efficiency and avoiding overheating, the motor is kept in the upper half of the speed range by adjusting the rider assistance to keep up sufficient road speed.

Most crank drive units use moderate power motors, so overheating is much less of an issue. Also most are effectively protected at lower speeds by using torque sensors, since less rider effort means less power applied so less heat. More rider effort means more power so speed rises, once again protecting against overheating.
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[mike killay]

Rated means that it's been tested/evaluated, and from the results, the engineer has decided that's what it should be. Continuous means exactly that. You can run your bike continuously on level one or level 5. The maximum continuous power is the maximum continuous power that the motor can run at without overheating. Put them all together and the rated maximum continuous power means that the engineer has determined the maximum continuous power that the motor can run at without overheating, and he's written it down in the motor's specification.

The user or manufacturer can, of course, run the motor above its rating, so the rating of 250w has little bearing on the actual power of you bike. The big problem with the rating is that it's also speed dependent. Because efficiency goes down at low speed, even a 250w motor run at 250w will overheat if it slows down too much going up a steep hill, so the engineer needs to apply a bit of judgement too when he rates it. You could be correct in rating what we'd call a 1000w motor at 250w if you wanted to be sure that it wouldn't overheat. Basically, nothing can be tied down. It's all a nonsense, so it would make sense to abandon the power limit and just have a speed limit.

Thanks, at last I understand
Mike

 

[flapajack]

Overheating is more likely to be an issue with hub motors...

Most crank drive units use moderate power motors, so overheating is much less of an issue. Also most are effectively protected at lower speeds by using torque sensors, since less rider effort means less power applied so less heat. More rider effort means more power so speed rises, once again protecting against overheating.
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This is the most succinct explanation of why crank drives are better than hubs.

Of course, the other advantages such as a natural riding experience helps too.

 

[Deleted member 4366]

This is the most succinct explanation of why crank drives are better than hubs.

Of course, the other advantages such as a natural riding experience helps too.

Overheating is only one factor though, and even that can be avoided by temperature control that you can find in some hub-motors. There's also hub-motors, like the Xiongda, that can automatically change to a lower ratio to keep it spinning in its efficient zone. You can't make sweeping statements that crank motors are better than hub-motors. You have to look at all the characteristics. Everything has advantages and disadvantages. You can only say that a particular motor's characteristics suit your style of riding. Have you tried a Panasonic hub-motor yet, like the one on the KTMs, or a Xiongda 2-speed? They might both change your opinion about which is best.

Also, whether you have a torque sensor or pedal speed sensor has nothing to do with the type of motor. You can have either with either - whatever you want.

 

[mechaniker]

About overheating

most overheating is at the Hub motors.
Problem on Hub motor is for two reason:
low speed and high current for example on a hill. The rpm is to low for efficient motor work and this means only a few watt is use by the motor to forward-power the bigger part of the battery consumption is simply change into heat

This brings us to Hub problem number two,
they are outer runners and the hub motor can´t transfer the heat to the Motorcover. Inside runs the Motor on a air-pillow of heat and no chance to transfer the heat because this is only possible at the slim axle shaft

Middrive Motors are inner runner means the inside is only some magnet rotate on an iron-axle (not sensitve for heat)
the stator (the heat-producer) is integrated into the Motorcover ,he can easy transfer his heat across the cover to the outside
advantage number two of the Middrive is that it is easy to keep this motor on a efficient level of rpm by switch to the next gear

But,
it is always the compromis you want go.
Hubmotor is high efficient on flat terrain and on higher rpm, higher efficient as the middrive
At the Hill the middrive have his advance because of better heat transfer and possibility to keep the motor on high rpm

like d8veh said:
there is no good or better you must choose the right motor for what you want this can be a hub and it also can be the middrive it depends on what is important for your need

I would choose a hub-motor for flat terrain and little hills because I like DD-drive´s silent power
If I would need a bike for hill area, I would choose a middrive


regards
frank

wow long writing hope my english is good enough to understand

 

[SteveRuss]

Overheating is more likely to be an issue with hub motors, since they include the most powerful e-bike motors. They are completely independent of the cycle gears used of course, so for efficiency and avoiding overheating, the motor is kept in the upper half of the speed range by adjusting the rider assistance to keep up sufficient road speed.

Most crank drive units use moderate power motors, so overheating is much less of an issue. Also most are effectively protected at lower speeds by using torque sensors, since less rider effort means less power applied so less heat. More rider effort means more power so speed rises, once again protecting against overheating.
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Thanks Flecc.

I'm still getting my grasp on these things and whilst i'm riding, i'm always trying to get the best out of the bike whilst respecting what's best for it.

My impulse 2 on my Kalkhoff Algine 8G seems pretty robust when I push it up some steep and long hills but i'm always reticent to go in to low gears (and a lower speed) when i'm heading up a steep hill and am feeling confident that I can maintain a higher speed in a higher gear.

If however it's better for the motor and maybe even the battery, then i'm happy to slow down and go down a couple of gears if that's the best way forward. Still trying to get my head around this stuff..

 

[Deleted member 4366]

It won't do any harm to use a higher gear. You get maximum power at about 2/3 maximum motor crank speed, but if you spin a bit faster, you might get a tiny bit more efficiency, but not enough to worry about. Just ride your bike how it's comfortable.

Frank, have you tried the Xiongda 2-speed yet? If not, you should. It's totally silent like a DD and can manage 30% inclines without overheating. The 48v one is much better than the 36v. The KT controller that comes with it, uses current control, so you get very comfortable power modulation. They're very cheap too.

 

[SteveRuss]

It won't do any harm to use a higher gear. You get maximum power at about 2/3 maximum motor crank speed, but if you spin a bit faster, you might get a tiny bit more efficiency, but not enough to worry about. Just ride your bike how it's comfortable.

Thanks. What do you mean though when you say 2/3 maximum crank speed? Sorry if i'm being dense..

 

[Deleted member 4366]

All motors have a maximum speed. It's easy to see if you have a throttle, but in your case, somebody will have to give it to you from the spec sheet. Probably about 100 rpm.