E-Scooter Idea

[rocky79]

Hello,

I want to build a light weight electric scooter that should move a person up to 250 lbs.
I was doing the basic power calculations and found out that I need at least 1000 watts motor. 24 v @ 42 amps max or 12 volts and 84 amps
Do you think a powerful Himax or similar brushless motor used for large scale electric planes will do the job?

I just wonder why the scooter companies like goped or schwinn still use lead acid batteries?

Any thoughts would help.

thanks

[orraman]

Rocky79,

I would like one of these for Xmas.
Li-ion please. :D

Dave

http://nycewheels.com/ezee-carro-electric-trike.html

The numbers might help.

Brushless

[rmteo]

The Schwinn electric bicycles use lithium polymer batteries.

http://www.schwinnbike.com/products/bikes_category.php?id=109

[rocky79]

Orraman and rmteo, Thank you for your replies.The websites did help. Those brusless motors seem to be at least twice if not more as big as a hobby outrunner brusless motor. I can easily find one that is 800 watts.

The thing I am not sure about is what kind of motor specs besides power i would be looking at for an electric scooter?

Thanks

[jeffs555]

Cost is probably the main reason for using lead acid. Not really up on the larger brushless motors, but I am sure if you could mount it and gear it properly you could find one that would work. This one at 6500Watts would probably have you doing wheelies. http://www.bphobbies.com/view.asp?id=V450327&pid=B3675243

[rmteo]

The other thing to consider is the cost of the batteries. Assuming you want work at 24V, 42A (about 1,000W) and get ONE hour of run time. The closest would be a 7S4P (25.9V, 40AH) battery using 10AH cells. Here is a 10AH LiPO cell:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3819

At $44.06 each, your 28-cell battery will cost you over $1233.

[jeffs555]

That Schwinn with the lithium is only 180 watts continuous and has a 10AH battery. They say 24v so not sure if it is 6 or 7 cells. Even at only 10AH, the battery is probably a large part of the $1500 cost of the whole bike.

[phil_g]

+You really should read this entire thread, its huge but gets interesting around page 73:
http://www.rcgroups.com/forums/showthread.php?t=566256&page=73
Theres a huge amount of information in there if you have the patience :)
Cheers
Phil

[andrew b]

This motor is only for the most advanced electric modelers. This motor is BIG, BAD, and very DANGEROUS! :D sounds great, an 8HP electric motor

[mjsas]

Here is a source of scooter parts.

http://www.electricscooterparts.com/

They have motors from 80 watts up to 1200 watts. They have a 300 watt brushless motor with built in speed controller for $39.95. Lead acid batteries give plenty of run time and for a scooter the weight is not a problem.

The engine cooling fan motors used in many cars are in the 200 to 500 watt range and would make good scooter motors. Look for Ford Escort fans, Denso makes fan motors for several brands and there appears to be four sizes used in 90's cars. The biggest size is large and the next size down would still be big enough.

[phil_g]

I recommend TNC Scooters, http://www.tncscooters.com
ask for Chris

One of the problems noted in the A123 pioneers thread is that sensorless brushless motors cog badly when loaded, ie on a scooter or any other vehicle drive chain which is physically holding back the motor as it attempts to spin up... sensored motors fare much better in this respect. The problem occurs mostly at low revs, so a centrifugal clutch would help, but then you're wasting the greatest benefit of going electric - ie full torque from stationary.
This was one of the reasons I went for brushed motors, they're so much easier for EV use and brushed controllers are way easier to home-brew.

Cheers
Phil

[rocky79]

I recommend TNC Scooters, http://www.tncscooters.com
ask for Chris

One of the problems noted in the A123 pioneers thread is that sensorless brushless motors cog badly when loaded, ie on a scooter or any other vehicle drive chain which is physically holding back the motor as it attempts to spin up... sensored motors fare much better in this respect. The problem occurs mostly at low revs, so a centrifugal clutch would help, but then you're wasting the greatest benefit of going electric - ie full torque from stationary.
This was one of the reasons I went for brushed motors, they're so much easier for EV use and brushed controllers are way easier to home-brew.

Cheers
Phil

Thank you phil! I appreciate the insight on motor selection.

[rocky79]

Here is a source of scooter parts.

http://www.electricscooterparts.com/

They have motors from 80 watts up to 1200 watts. They have a 300 watt brushless motor with built in speed controller for $39.95. Lead acid batteries give plenty of run time and for a scooter the weight is not a problem.

The engine cooling fan motors used in many cars are in the 200 to 500 watt range and would make good scooter motors. Look for Ford Escort fans, Denso makes fan motors for several brands and there appears to be four sizes used in 90's cars. The biggest size is large and the next size down would still be big enough.

Wow! that site has so much parts. Thank you for sharing!

[Yimmy]

here's another website to check out. http://electricscooterparts.com/motors.html

[Amberwolf]

One thing besides raw power you should look at in the scooter is RPM vs torque. You need torque way more than you need RPM. Pick something that spins only as fast as you need to go at maximum speed, when it's at it's full rated voltage. Some give RPMs per volt instead of a max speed vs max voltage rating.

Since the motor should take less current when operating at max speed vs startup (stall) speed, it will require less power that way. Of course, with the load on it it will still take more current to run than simply free-running it, but not as bad as if you pick a motor designed for 3000RPM and load it down to 90RPM. :)

Also, if you pick a motor that runs at the speed you need it to at max to turn the wheels fast enough to get you the max speed you intend to go, you will not need additonal reduction gearing beyond the chain/sprocket system (or belt or friction drive) you will already be using.

That's a complication you don't need, as it adds unnecessary weight and friction losses to your powertrain.

I've been struggling to find myself a motor I could recycle for my ebike conversion project (http://opporknockitytunes.blogspot.com) , and finally decided to just build one for it, from an old cieling fan AC motor, as it appears to be made well enough to be worth rewinding and adding magnets to turn it into a BLDC. The harder part is the controller for brushless, because I don't want to deal with PICs or other uC's, but may have to resort to that anyway.

[rocky79]

One thing besides raw power you should look at in the scooter is RPM vs torque. You need torque way more than you need RPM. Pick something that spins only as fast as you need to go at maximum speed, when it's at it's full rated voltage. Some give RPMs per volt instead of a max speed vs max voltage rating.

Since the motor should take less current when operating at max speed vs startup (stall) speed, it will require less power that way. Of course, with the load on it it will still take more current to run than simply free-running it, but not as bad as if you pick a motor designed for 3000RPM and load it down to 90RPM. :)

Also, if you pick a motor that runs at the speed you need it to at max to turn the wheels fast enough to get you the max speed you intend to go, you will not need additonal reduction gearing beyond the chain/sprocket system (or belt or friction drive) you will already be using.

That's a complication you don't need, as it adds unnecessary weight and friction losses to your powertrain.

I've been struggling to find myself a motor I could recycle for my ebike conversion project (http://opporknockitytunes.blogspot.com) , and finally decided to just build one for it, from an old cieling fan AC motor, as it appears to be made well enough to be worth rewinding and adding magnets to turn it into a BLDC. The harder part is the controller for brushless, because I don't want to deal with PICs or other uC's, but may have to resort to that anyway.

That's a million dollar advice about the torque and rpm. I was reading a book about electric motors and they mention exactly that. Thank you for sharing!

I want to build a really light scooter so more weight than needed is a definite no.
I am still in the planning phase ( motor selection) frame design and all the other parameters.

As far as controllers I am planning to use one off the shelf.

Cheers!

Rocky

[Amberwolf]

You should blog your whole creation process! From design ideas to finished scooter--it'd be really nifty to read that. Blogspot is free and works well (if you already have Gmail just use that as your login, since Google runs both). It's what I am using to track the Electricle™ project.


If you're interested in making your own motor for the purpose, it's possible, and might not even be that hard, depending on how lucky you get with scrounging. If you're just making a Brushed DC motor, rewinding it with bigger wire or more turns or more poles, or replacing it's magnets with more or stronger ones would be reasonably easy to do, depending on how technical you are and how deep into design you want to get. .

I couldn't find a motor big enough to do what I wanted that I could afford, so I decided to make my own, and this is the first step towards it. I'm not doing anything really technical yet with it, since I have yet to calculate anything about what specifics the motor will need to have. At the moment, I'm just throwing junk together to get motion. :-)

I tested a version of an AC-cieling-fan-to-brushless-DC motor conversion and posted a video of it working (where you can hear me rambling) on my blog in this post:

http://opporknockitytunes.blogspot.com/2007/12/bldc-motor-test-proof-of-concept-with.html

This is a direct link to the video, (http://www.blogger.com/img/videoplayer.swf?videoUrl=http%3A%2F%2Fvp.video.goo gle.com%2Fvideodownload%3Fversion%3D0%26secureurl% 3DqAAAAIiSxp13MRsP2RXZVN7myjKRxvpjAuG5DCAR0MkCKMHG mpq2hGL7HQ3Qj3bpz2RzURGaJZmPGbcCUhJIbwAn1k1M-7ghRSvNYyXkUPySzGnQkWkEYulUTzr9FyiV3plZeVUxLZKzKc0 EgyY9ICOwNp422U_yoc245l8SrJ_JpiQbkMjqQPrCfuJzOizME 74SNN7y70CGt26I0HnJ8HCv2OITQDA0AwdwWcA_ysK9Ape1%26 sigh%3Dg8qn72DxlsXg01WOQ10wDmTpyzc%26begin%3D0%26l en%3D86400000%26docid%3D0&nogvlm=1&thumbnailUrl=http%3A%2F%2Fvideo.google.com%2FThumb nailServer2%3Fapp%3Dblogger%26contentid%3D687f449f ac6437d%26offsetms%3D5000%26itag%3Dw320%26sigh%3Dd MWbO3550sXgBq0-fLqLIb9UQhU&messagesUrl=video.google.com%2FFlashUiStrings.xlb% 3Fframe%3Dflashstrings%26hl%3Den) in case you don't want to scroll
thru the rest of my blogpost, which will open in a new tab or window, depending on your settings.

I thought it was really cool that it worked at all, considering the junk I used to do it with, and that the actual time spent to do it was less than an hour and a half, not counting all the fiddling around with stuff I did that wasn't necessary to just get this working. It won't run the bike yet, but it's a proof-of-concept.

Yes, you *can* turn a cieling fan, some harddisks, and a laser printer into a bike motor. :-)



--

--
Michael Elliott
Opporknockity Tunes Studios, Uninked
Phoenix, AZ
Bicyle Conversion Blog: http://opporknockitytunes.blogspot.com

[rocky79]

I compiled useful equations for selecting the appropriate electrical motor parameters needed for a particular task.
A. Rpm Calculation:

RPM= Kv x (Vin-ImRm).
Vin is the applied voltage.
ImRm is the resistive voltage drop across the motor winding due to copper loss.
Kv is Voltage Constant = RPM/Volts.

B. Torque Calculation:
Torque= Kt x (Iin-Io).
Io= No load current (leakage current).
Kt is the torque constant = (Inch-OZ)/ Amp.

C. Kt x Kv = 1355.
D. Max mechanical power is produced when the motor is loaded until the RPM is half the no loaded RPM. ( Don’t do it)
E. Choose the proper motor so that the power required from the motor is when the motor is operating at a point near it’s best efficiency.Therefore it will be running at it’s coolest temp.
F. Hysterisis loss is a loss due to the fact that the armature must be magnetized and reverse magnetized every single revolution of the motor shaft.
G. Watch for cogging that can cause severe resonance in gear boxes and long drive shafts.
H. Motor heat at Stall is :
Heat at stall=Vin x Istall=Vin/Rm (where Rm is the copper winding resistance).

I. Input power Pin (watts) = Vin x Iin.
J. Output power Pout= Torque x RPM.
Pout= Kt (Iin-Io) x Kv(Vin-ImRm). Where Kt x Kv = 1355

Pout(watts) = (Iin-Io) x (Vin-ImRm)
1 hp=746 watts.
K. Efficiency = Pout/Pin.
L. Imax efficiency= SQRT( Io x Istall).

[ZAGNUT]

if designing your own motor then set it up to run at 1:1 with the RPM you need at the rear wheel. this eliminates any need for gearing, chains or belts and lets you integrate the motor into the wheel hub itself. saves lots of weight and space.




dave

[DavidB.]

1:1 gearing will not be a good idea. A reduction will allow a very small lightweight motor to be used, and I believe the idea is to have something lightweight. My scooter in the links above tops out at almost 40mph and is seriously fun to ride :) The new larger HXT motors at www.hobbycity.com would be even better I'm sure and still only weight 3lbs or so.

[rocky79]

1:1 gearing will not be a good idea. A reduction will allow a very small lightweight motor to be used, and I believe the idea is to have something lightweight. My scooter in the links above tops out at almost 40mph and is seriously fun to ride :) The new larger HXT motors at www.hobbycity.com would be even better I'm sure and still only weight 3lbs or so.

David, I am interested in your 40mph scooter, I don't see the link. What motor did you use?

Thanks

[DavidB.]

+You really should read this entire thread, its huge but gets interesting around page 73:
http://www.rcgroups.com/forums/showthread.php?t=566256&page=73
Theres a huge amount of information in there if you have the patience :)
Cheers
Phil

Here it is