E-bike battery charging while riding
- Thread starter LI-ghtcycle
- Start date
Ok, the latest update to the project :
I'm looking at dc motors and found this
https://electricscooterparts.com/motors24volt.html
It's the motor just over halfway down ($119.99)
How do I work out how which sprocket I need? 9, 11 or 13 teeth - sounds like how we rate the women in a few counties here, but I need to know how the sprocket suits a standard 26" wheel mountain bike.
24V 450W electric bicycle motor with built-in gear reduction transmission. Output shaft speed is 550RPM. Includes 9 tooth sprocket for 1/2" x 1/8" bicycle chain. 11 and 13 tooth sprockets are available for this motor. Output shaft is 11mm OD with a 4mm wide x 2mm deep keyway. Powerful four brush permanent magnet design. 100% ball bearing construction. 24" long power leads. Shaft rotation reversible by reversing power leads. Three bolts on front side of motor for mounting. Mounting bracket is available for this motor. Motor dimensions: 4-1/4" outside diameter x 3-1/2" long excluding transmission and output shaft, 4-1/2" long including transmission and output shaft.
The site doesn't give an email address otherwise I'd ask there!
Thanks
I'm looking at dc motors and found this
https://electricscooterparts.com/motors24volt.html
It's the motor just over halfway down ($119.99)
How do I work out how which sprocket I need? 9, 11 or 13 teeth - sounds like how we rate the women in a few counties here, but I need to know how the sprocket suits a standard 26" wheel mountain bike.
24V 450W electric bicycle motor with built-in gear reduction transmission. Output shaft speed is 550RPM. Includes 9 tooth sprocket for 1/2" x 1/8" bicycle chain. 11 and 13 tooth sprockets are available for this motor. Output shaft is 11mm OD with a 4mm wide x 2mm deep keyway. Powerful four brush permanent magnet design. 100% ball bearing construction. 24" long power leads. Shaft rotation reversible by reversing power leads. Three bolts on front side of motor for mounting. Mounting bracket is available for this motor. Motor dimensions: 4-1/4" outside diameter x 3-1/2" long excluding transmission and output shaft, 4-1/2" long including transmission and output shaft.
The site doesn't give an email address otherwise I'd ask there!
Thanks
Chalo
100 TW
Is that for propulsion or for use as a mechanical generator? Those are Unite brand brushed motors, which are quite inefficient by today's standards.
I used a 350W Unite motor in a stationary generator bike once upon a time. I made a two stage chain drive to get enough RPM to charge a 12V battery, 60/16 on the first stage and 90/11 on the second. It worked as intended, but high efficiency was not of paramount importance in that case.
I used a 350W Unite motor in a stationary generator bike once upon a time. I made a two stage chain drive to get enough RPM to charge a 12V battery, 60/16 on the first stage and 90/11 on the second. It worked as intended, but high efficiency was not of paramount importance in that case.
It was going to be for propulsion until I realised I'm building a 36v battery... 
I read a post on rc motors and Bobc managed to get 20miles at 20mph out of a cheap outrunner so I'm aiming for something similar. Waiting to hear back about how many Kv I need so will update this post when things have moved on a bit.
Thanks
I read a post on rc motors and Bobc managed to get 20miles at 20mph out of a cheap outrunner so I'm aiming for something similar. Waiting to hear back about how many Kv I need so will update this post when things have moved on a bit.
Thanks
Hey Dudes,
It's a known fact that if you spin a motor it generates electricity.
Why not take a rear hub driven bike that can reach 55km/h and stick a small standard 250w passive hub in the front wheel to charge the battery while riding?
Will it generate enough power to charge the bike in a way that it will extend the battery life in a decent percentage or will it be minor and not worth it?
It's a known fact that if you spin a motor it generates electricity.
Why not take a rear hub driven bike that can reach 55km/h and stick a small standard 250w passive hub in the front wheel to charge the battery while riding?
Will it generate enough power to charge the bike in a way that it will extend the battery life in a decent percentage or will it be minor and not worth it?
keithmac said:
I didn't say that it would give back 100% of what it puts out.
Basically the front hub is pretty easy to spin by hand as it is pretty small so why wouldn't it be able to give a bit of charge?
There is another thing to add to the equation and that is that you don't have to power the rear hub in order to have the bike rolling, you can use a bit of throttle and then stop giving the rear motor juice and the front keeps spinning, especially on declines.
You're talking about "regenerative braking", often referred to as regen. The entire time the front 250W hub is generating electricity, it is also causing drag. This has been tried before, and there is more drag than regen watts going to the battery.
The front motor would have to be a direct drive hubmotor, and it would be useful as a magnetic brake for very long and steep downhills. However, on flat land this would be easy to test.
Put a cheap watt-meter on the rear hub and measure it's steady-state watts drawn at its top speed. Then add the front hub, set up for max regen, and then measure the watts drawn by the rear hub at a steady top speed on flat land. Finally, put the watt-meter on the front hub to see how many watts it is putting into the battery.
The front motor would have to be a direct drive hubmotor, and it would be useful as a magnetic brake for very long and steep downhills. However, on flat land this would be easy to test.
Put a cheap watt-meter on the rear hub and measure it's steady-state watts drawn at its top speed. Then add the front hub, set up for max regen, and then measure the watts drawn by the rear hub at a steady top speed on flat land. Finally, put the watt-meter on the front hub to see how many watts it is putting into the battery.
spinningmagnets said:
I didn't talk about regen braking, but only to use the front hub as a charger.
If you say that it has been tried and it didn't work then it will be probably useless for me to try and expect different results, and even if different, it would probably be just a bit better than what most tried which still doesn't worth it imo.
I was thinking just now about something else...
Why not throw out the extra front hub idea and just use the electricity that the powered hub is creating while it has no power driven in to it.
For example, on declines and when you let go of the throttle and keep rolling.
You shouldn't count the drag since it is already there, nothing added, PLUS my rear hub is a 7.8kg beast which can generate alot more than those small 250w hubs.
Also, if connecting the phases to the battery is problematic since when I use the throttle it throws current into the phases then it's possible to make a simple relay that will connect the hub wires to the battery (in order to charge it) only when the throttle is at 0 position.
Thanks alot for all the info.
Seems that it's better to have a clutch system because the motor drag will always be greater than the regen but when you don't really have a clutch to disconnect the motor on downhills for example then regen works (not so much in the city though).
Seems that it's better to have a clutch system because the motor drag will always be greater than the regen but when you don't really have a clutch to disconnect the motor on downhills for example then regen works (not so much in the city though).
izeman
1 GW
Forget about all the drag stuff. You can't get more energy out than you put in. It's that simple.
Every watt the front motor 'produces' has to be 'produced' by the rear motor. Or vice versa.
Every watt the front motor 'produces' has to be 'produced' by the rear motor. Or vice versa.
If you want to charge the battery with a passive hub motor, you will need to turn that passive hub motor.
How can you turn this hub motor?
If the passive hub motor is 100% efficient and you want to charge at 100 W then you need to put in 100 W (to move it) only to get out 100 W. You did not gain anything.
How can you turn this hub motor?
If the passive hub motor is 100% efficient and you want to charge at 100 W then you need to put in 100 W (to move it) only to get out 100 W. You did not gain anything.
Thanks guys, I wrote this in my message above, I just learned that fact BUT the regen thing does exist and IS efficient as the hub motor that drives the bike, when not connected as regen is just creating drag and not giving the power that drag makes back, so instead of wasting that drag that is already there, why not use it to throw back a certain percentage back to the battery.
What I don't get is how the regen mode is triggered.
Basically it should be, whenever the throttle is not applied but from what I read it is connected to the brake lever which is a waste since all those declines when not using the brakes would not trigger the regen mode.
Why don't the controllers have an option for an automatic regen mode whenever throttle is not applied?
I thought about hacking this in a McGyver kinda' way by having a small momentary on/off button on the twist throttle and when the throttle is at zero point there will be some kind of a plastic thingy pressing the button making regen mode work. what do you think?
What I don't get is how the regen mode is triggered.
Basically it should be, whenever the throttle is not applied but from what I read it is connected to the brake lever which is a waste since all those declines when not using the brakes would not trigger the regen mode.
Why don't the controllers have an option for an automatic regen mode whenever throttle is not applied?
I thought about hacking this in a McGyver kinda' way by having a small momentary on/off button on the twist throttle and when the throttle is at zero point there will be some kind of a plastic thingy pressing the button making regen mode work. what do you think?
izeman
1 GW
you still really miss some things 
the 'drag' you feel comes from the permanent magnets binding to the stator. it does NOT produce any useable energy. to transform the revolution of the wheel into electric energy you have to connect a controller that is put in 'regen mode'. doing this adds A LOT OF DRAG to the wheel.
but all this comes to the same conclusio as already mentioned: there is NOTHING LIKE FREE ENERGY.
the automatic regen think sounds like a good idea, and it DOES exist with several controllers. BUT you can't COAST, as regen will brake the wheel and slow down the bike. the more energy you 'win' the harder the deceleration will be.
the 'drag' you feel comes from the permanent magnets binding to the stator. it does NOT produce any useable energy. to transform the revolution of the wheel into electric energy you have to connect a controller that is put in 'regen mode'. doing this adds A LOT OF DRAG to the wheel.
but all this comes to the same conclusio as already mentioned: there is NOTHING LIKE FREE ENERGY.
the automatic regen think sounds like a good idea, and it DOES exist with several controllers. BUT you can't COAST, as regen will brake the wheel and slow down the bike. the more energy you 'win' the harder the deceleration will be.
Oh, so there is no regen without braking...
But without putting the controller in regen mode, if you just spin the wheel with the hub by hand and measure the phases with a volt meter, there is energy coming out of the wheel, so why can't this energy be used the way I said without actually using the regen mode (that will generate more power) and only the use the regen mode for slowing down?
But without putting the controller in regen mode, if you just spin the wheel with the hub by hand and measure the phases with a volt meter, there is energy coming out of the wheel, so why can't this energy be used the way I said without actually using the regen mode (that will generate more power) and only the use the regen mode for slowing down?
izeman
1 GW
rg12 said:
there is VOLTAGE not CURRENT. as soon as you connect a RESISTOR between those phases (or just connect two of them together) you will notice that it's much harder to turn the wheel. and it takes at least 100%+ (not the '+') power to turn the wheel compared to the energy you produce. there is NO 100% efficient machine in this world. and there are even FEWER machines with a 100%+ efficiency :wink:
This will not harm you motor in any way - it's a standard diagnostic test for shorted motor phases.
Here it will demonstrate the effect of actually using the motor to drive a load.
The difference is caused by the large current flow in the motor operating in 'generator mode' instead of just producing a voltage with essentially no current as when only measured with a voltmeter. This drag is what causes regen braking.
(Done as a normal test, if your phases were shorted, there would be no change in required force because the generator effect would be reduced or eliminated by the coils being shorted out - so no 'generator effect'.)
Here it will demonstrate the effect of actually using the motor to drive a load.
- Put the bike on a stand.
- Turn off your controller.
- Turn the wheel and note the force required.
- Unplug two phase wires and short them together with a bit of wire or a paperclip.
- Turn the wheel and again and note the force required.
The difference is caused by the large current flow in the motor operating in 'generator mode' instead of just producing a voltage with essentially no current as when only measured with a voltmeter. This drag is what causes regen braking.
(Done as a normal test, if your phases were shorted, there would be no change in required force because the generator effect would be reduced or eliminated by the coils being shorted out - so no 'generator effect'.)
teklektik said:
Yup, just learned that when I bought a motor that was separated rotor from case so when I assembled it I thought that there was a problem because it was sometimes spinning smooth and sometimes very "coggy" and then I noticed that the "sometimes" part is when the phase wires touch each other or not which happens on and off since they are tied very close.
btw, was my idea of using a momentary on/off button for turning the regen on/off is how most people do it or they connect it to their brake lever power cut off wire?
induna
100 mW
It's pretty obvious that the OP just has some basic misunderstandings about physics. Whenever energy is transformed from one medium to another energy is lost, and it certainly can not be gained. There is no such thing as a 100% efficient transformation. So, using some made up numbers, here is what happens if you try to do what the OP suggests.
Assume it takes 100W to move your bike at 20kph. You add a second hub motor to the bike and put it in regen mode, and it also takes 100W to push that new hub at 20kph. The hub in regen mode can only charge the battery at 90W due to losses. So with the second hub in regen mode it now takes 110W to go 20kph instead of 100W. It takes 100W simply to move the bikes at 20kph plus 100W to turn the extra hub in regen mode less 90W gained from the energy put back into the battery by regen. It is important to note that even if everything were 100% efficient, which it cannot be, the best you could hope for would be to break even, at the cost of greater expense and complexity.
Assume it takes 100W to move your bike at 20kph. You add a second hub motor to the bike and put it in regen mode, and it also takes 100W to push that new hub at 20kph. The hub in regen mode can only charge the battery at 90W due to losses. So with the second hub in regen mode it now takes 110W to go 20kph instead of 100W. It takes 100W simply to move the bikes at 20kph plus 100W to turn the extra hub in regen mode less 90W gained from the energy put back into the battery by regen. It is important to note that even if everything were 100% efficient, which it cannot be, the best you could hope for would be to break even, at the cost of greater expense and complexity.
izeman
1 GW
Both ways are ok. Some ppl like to control when regen happens and eg. only use it when going down long hills, some like to save brake pads and get maximum energy efficiency and use it all the time.rg12 said:
If your controller's regen setting is too high it can even be that you will lock yoir tire on slippery ground. This may be unwanted as well. So with a momentary button YOU can decide from situation to situation when it's appropriate to use.
Also don't expect too much savings. I ride quite aggressively, so my savings where quite below 10%. If you live in hilly terrain and ride smoothly and use regen a lot it can be more than that. But no where in the range of 30%!
izeman said:
Wow, I didn't know that the regen brake is that strong...I have to try it now
Even if you save 5%, why not use it? it does save brakes a bit (especially on ebikes which go fast and usually are heavy too) and you also get like that low gear feature of cruising slowly down a steep road and the number one reason is, if you already have that feature in your controller then it doesn't require any effort or money, so even for 5% gain, there were times when I got power cut offs by the controller when I could have paid $100 for those 5% as my single speed downhill setup has a giant hub motor that you need to be a professional athlete to pedal it.
Little tip btw for those who want big power: if you can settle for a lower powered hub while using vents, thicker phases and such, do it as using those 8-11kg hubs is bitc**** when pedaling or lifting them heavy a$$ bike. just my 2c
rg12 said:
It's only easy to turn when not connected to anything. As soon as you take any power from a generator, it becomes much harder to turn.
You can do a neat little trick, which I used to do for the school kids: Take two small electric toy motors and connect them together with a pair of wires. When you turn one by hand, the other turns by itself. That's an excellent way to make a remote control. It's like they're joined by gears even though they're three feet apart. Then jam one so that it can't turn, and try to turn the other. You can't.
Voltron
1 MW
Yes to some of your newer ideas rg. You can use a push button at the handlebar to trigger the regen... Vintage Electric bikes has it set up that way. And yes, triggering it without hitting the brakes is also doable... Stromer uses a thumb pad you can lock the regen on with, and vary the levels with, so you can coast down a mountain slowing down and charging the whole way without pulling the brakes constantly. There's lots of new controllers that you can choose to apply the regen as the throttle is let off, or presets, or second throttle that varies the regen, there's lots of choices. But none of those apply if you have a geared hub motor with a clutch, or a crank drive, or anything but a direct drive hub motor, which is why a good chunk of people aren't that into it. Also newer batteries have so much range that the extra miles with regen aren't as important, and many use it more as a brake than a range booster. You also have to beef up your torque arms to handle the axle rocking back and forth between driving the motor and regening it.
Separate from all that, recapturing any extra energy while coasting without slowing down is just flat out impossible, and trying it while driving the main motor is even worse. Any second motor or any other system for regen during slowing for stops or long downhill coast will be heavier and less efficient with all the extra losses thru the wire resistance and drag when not in use than just using the one motor for everything.
Separate from all that, recapturing any extra energy while coasting without slowing down is just flat out impossible, and trying it while driving the main motor is even worse. Any second motor or any other system for regen during slowing for stops or long downhill coast will be heavier and less efficient with all the extra losses thru the wire resistance and drag when not in use than just using the one motor for everything.
