Electric bike power
 

I am in the process of building an electric bike and all I need is the battery system. I am going to run it at either 36 or 44 volts, so 10-12s lipo or a bunch of a123 cells will do the duty. So far I have a big honking astro 90 and a "little" 3032 scorpion with appropriate OEMRC ESC. Both are rated at 1200w continous. I want to test the difference in efficiency between the systems and see which one works out for the best.


Now for the hard choice. Batteries! I would like to use lipo because it has a higher power density, and for my projected amp/hour rating it will only take 2 or 3p to get 10 to 15 amp hours. I would like to use a123 for the fast charging (if I have enough power :lol:) and the longevity of the cells. The downside is that I will need 5 or more parallel banks for runtime.


What do you guys think about it? Charging seems to be the toughest part about the whole matter.

The little 3032 isn't really designed to handle 36 volts. Remember it's going to be carrying a pretty big load. (your butt) LOL

I played around with this idea using several different outrunners on 4S.

I used a 1" Diameter rubber Wheel and put it in a Prop Adapter for an Airplane. Then used one of those touring bike tires on the front, looked almost like a slick for the best contact.

I made a spring loaded motor bracket that would apply constant pressure between the drive and the front wheel.

A Quark 80amp Esc and a Servo Tester to operate it with. It had a little dial to turn it up and down with.

The 3520 would carry me about 20mph for a couple of miles on 4000mah. Then I tried a Century 600 plus, a 3530 I believe. It carried me up to 28 mph for a couple of miles. But both motors ran really hot and wouldn't have held up to this kinda treatment for very long.

Get one of these. http://www.unitedhobbies.com/UNITEDH...idProduct=5139

It's 12mm shaft is very close to the standard 1/2" 1/2" converted is 12.5mm fyi

Being rated for 7000watts, it will put out over 9hp. The price isn't bad either. In fact, I have one I'll sell/trade you if you're interested. On the condition that you let me know how this all works out and by all means, don't get yourself hurt. LOL

For Power, 10S A123 is the way to go. Their Tough and are gonna give you good cycle life. Charging this isn't really an issue. Just use the factory Dewalt Charger Base.

I'm sure you've been inside a few packs like I have to gather cells for other projects. You can use one empty case with the Battery Management Circuit inside to charge the entire thing.

Leave the Circuit inside the Case and jump off the power leads to your own connectors.

If balancing is a concern, you can make your pack parallel by jumpering between each cell. Then carry these connections to the single Battery Management circuit that's transferring power from the charger.

These are some of the ideas that I thought about putting to work on this.

The big outrunner probably has enough torque to drive the rear tire with chain drive. I was thinking about mounting a stepped sprocket on it so I could find the ratio that it operated at best. Have it take the place of the regular front sprocket, and retain the gear changing ability if I could.

The big motor should be able to put out enough power to go as fast as you care to go. It's all a matter of how much juice you wanna feed it. LOL

I bet it would really accelerate hard too. :yes:

I will be rewinding the 3032 for 36v use of course. I think it will be enough to handle the job, but that is why it is called trial and error and not trial and success, lol!

a123 does sound good. I have really been leaning to that solution, although I have seen some really smoking deals on 18c and 20c lipo packs lately. I just don't want to deal with the charging nightmares mostly.

I will be using a pocket bike CV tranny with external chain reduction too. This way I can mess with gearing and still have a decent top speed. The biggest hurdle so far has been getting the reduction in a small enough package for the tiny bike, hence the pocket bike tranny. I only want 30mph on a 12" tire, so that is 6:1 reduction on a motor that spins only 6k rpm. The second choice is to take the belt drive system out of an old washing machine. I would just need to weld or make a hub carrier for the rear pulley.

Look at this guys conversion. Pretty haus motor. http://www.rcgroups.com/forums/showthread.php?t=804254

This is a very intriguing idea... I've already got an old mountain bike with 24" wheels and a rear derailleur and without pedals, an OEM RC Sentilon 12s Lipo 100amp ESC, an Astroflight servo tester, 4 x 12v 7Ah lead acid batteries, and 2 x 5s2p A123 packs + an extra 1s2p. If I could get that gigantic outrunner from United Hobbies that sike linked to, a suitable chain-drive "pinion gear" from http://www.spd-si.com , and mount everything, then I'd have a fully functional electric bike... Now onto Brian's calculator to figure out what size "pinion gear" I would need to achieve 30mph.

EDIT: The motor sike linked to is 180kv. Based on calculating gear ratios, it would require a reduction of 22:1 to run at 30mph tops with 26" tall tires and 48v. I did find that they have a 130 kv version of the same motor:
http://www.unitedhobbies.com/UNITEDH...idProduct=5142
With the same tires it requires only a 16:1 reduction.

Your geardown will be the hardest part. You will need 24x total reduction to drive the wheel at 30mph with a 6k rpm motor.

Alot of 18 speeds on the market now, have a stepped sprocket in the rear with 6 steps.

I've never counted the teeth, but next time I'm down at the local Walmart, I'll check that out and make a note.

My little experiement pushed me to 28mph, and it felt like I was flying. I got down to the end of the road about 2 miles out and the battery went dead. Then I realized I had covered alot of ground pretty quick when I had to peddle back. LOL

Most 6 speed freewheels are 14-28 (14t small, 28t large), wide range shimano are 14-34. The downside to using one is that you lose braking power via the motor, and they really can't take much power. A cassette could be used, and a fixed trials hub would get rid of weak pawls. I welding the freewheel to the hub is an easy and cheap solution.

I guess I will have to deal with braking on my CV tranny anyway, since the belt wont have much grip for braking in reverse. On top of that, my ESC's wont have braking. Doh!

guess what i might build:
i already have one of these:
http://www.amazon.com/Baja-Motorspor.../dp/B0006UEX5W
and i was thinking one of these
https://www.unitedhobbies.com/UNITED...idProduct=5142
one of these
http://www.horizonhobby.com/Products...ID=CSEPHX110HV
and 2 of these in series
https://www.unitedhobbies.com/UNITED...idProduct=4289

:party::party:

Ever saw the electric version of the goped? it moves well. it uses lead batteries.

here is a dutch company that makes electric bikes;
http://www.sparta.nl/nl/sparta-ION-p...0001&menu=1com
They use ion batteries, look at the funky lower tube, that's where they hide the batteries.

Their rear hub is a large BL motor. It supports up to 25 km/h (so i guess it produces roughly 180 watts of power)
It's not really considred an electric bike, it's a bike withe electric support. I don't know what your goal is?

Those HXT outrunners at Hobbycity look like they could work well. The site says it replaces a 60-80cc engine. A lot of pocket bikes use 49cc engines and can push you to the 40mph area with one speed, so that outrunner should do ok.

I'd like to see an electric pit bike, but use the original transmission and sit the motor where the crank of the engine would usually be. I would look more professional than some of the custom e-bike around and it can't hurt to have multiple gears.

I've always thought about an electric push bike with the batteries inside the frame. Makes it look a lot neater than a brick hanging off the side.

I do have a pit bike that could be converted in the future. It is a drz 110 with a 140CC kit and all the works. Maybe in the future it will get converted. Right now the liquid fuel is a much denser power delivery tool :D I like the ideas of multiple gears.

I remember a thread where there was some links to some electric bikes and motors But i couldn't find it

Do you mean this one? http://www.rc-monster.com/tempforum/...read.php?t=487 It was in the temp forum.
Wonder if Brian ever started it.

Been doing some thinking/designing and parts locating for my bike. It looks like the cost is going to be ~$300 on top of the ESC and batteries that I have already. Here is a parts list:
http://img.photobucket.com/albums/v1...bike_parts.jpg

As I stated in a previous post, this bike needs some major reduction, 16:1 for 30mph. The largest "spur gear" (sprocket) on the wheel is a 28t, so I'll be using that. That sprocket will mate with an 8 tooth sprocket attached to the output of the reduction unit. A chain of the same size as stock will be ordered, and this chain should handle a larger load than the stock bike chain. So far, it has a reduction of 3:1.

On to the reduction unit. I would put some mod 2.5 gears (or something like that) in the reduction unit, but those gears are just too darn expensive and would require more precision alignment. From SDP-SI I found "ladder chains" and matching sprockets, so I found a combination (11t "pinion" and 54t "spur") that should work well. The 11t sprocket will go on the motor (requiring either a sleeve to convert the 12mm shaft to the 1/2" ID of the sprocket or a new shaft), and the 54t sprocket with hub will sit on a 1/2" diameter shaft, which will be supported by bearings. This unit will give a reduction of 4.19:1.

That's a total reduction of 14.5:1, which isn't exactly what I'm looking to get, but an extra couple MPH won't hurt. Anyone have any opinions/crticism on this setup?

No, I never did. The lack of disc-golf partners kinda withered my interest in the game, and I had (and still have) other things on my plate. It's all I can do to fund my R/C projects let alone dump cash into experimental projects. It's still something I'd like to do though.

However, I've been eyeing my Mazda 3 thinking that a BL system driving the rear tires may give those turbo'd MazdaSpeed 3's and STi's a little run for their money, especially in the 1/4 mile. Keeping gas powering the front and adding "only" around 30HP (but tons of torque) to the rear would be fun! Since BL has max torque at 0 rpm, it would help get me off the line where the gas engine is the weakest. A hybrid, but for a different reason. :smile: But, 200v/150A ESCs are hard (and expensive) to come by...

You could cut a lot of cost off if you have a farm implement/ yard tractor place around you. Gears for combines and brush hogs can be bought there, as well as many chain sizes.


Seems like a good setup. Just make sure you have enough room for the 54t sproket on the bike, the gearbox to house it will be bigger than your motor most likely. You have the skills to pull it off pretty clean, I would love to see it.

This may be a silly idea but if gearing down enough is an issue why not just use 2 chains. It has been done on some mountain bikes. So have a chain coming off the motor going to another chain which goes to the back wheel. It would make changing gear ratios easier and cheaper.

That is what MetalMan and myself are doing. My first reduction stage will be a pocket bike tranny.

Thanks for the idea, I'll see if I can find a place like that.

The 54t gear actually won't be too big, only about 6.5" in diameter. The motor will mount directly to the gearbox, so this unit won't take up too much space.

Ididn't understand but it sounds good. When I first read this I thought you were talking about an RC motor bike. This should be good to see. I'll be interested to see if you can make something that can beat good old human power.

You may want to take just a regular bike (the pedaling kind) and try putting a BL system in that. You already have the gears and for me to be going 25-30mph on the flats I know that I need to put out about 350-400 watts. Thats not very much, you could get over 50 on a system that would put out 2000 watts continuous.

Uh-oh, what have I gotten myself into... One of these is now on its way to me:
http://www.hobbycity.com/hobbycity/s...idProduct=5142
$150 + $43 for EMS Express shipping! I opted to pay the extra $12 on shipping over the Air Parcel option. Supposedly the shipping time is 3-5 days, I'm getting anxious!

Now it's time to start collecting some of those specialty sprockets and chains for the reduction unit (JRH, I know, I could save a lot if I just look around, so I will). However, if I don't find anything soon I will just order the ones I posted from SDP-SI since they aren't normally stocked and will require me to wait for them to be made.

I have been trying direct tire scrubbing drive over the past few days. I think I will need a wind for 36v to work proper, the 11.1v wind of the scorpion 3032 doesn't work as it overheats. The startup with a MM is also much too hard, as the tire scrubbing force is pretty great. I am seeing if I can get a proto with a knurled case. In the mean time I may try an epoxy/ sand coating. The can face speed is 15mph, which is right where I want it.

I haven't started my gearbox drive bike yet. I want pedal assist so the rear hub will be the tricky part.

lol, you think that 7 ft-lbs of torque will be enough? And that's just the motor (@130A) without any gear reduction.

I hope so :lol:. And to think, that's before an ~14.5:1 gear reduction!
Initially the motor will probably run at 24v, and if I have enough balls, then I might try 48v :surprised:.
Who wants to make a bet on how fast it will push me? (it will still have a rear dérailleur, and I weigh 165lbs).

In that case, you need two of those running at the full 48v. 14.5:1 gearing will give you 101 ft-lbs of torque. For two motors, that's 202 ft-lbs, but only 17.4HP (130A X 48v X 2 motors). :lol:

No sir, I've got no idea what it was.. I heard no motor, only squeaking tires..

I just got version one working. 6s a123, mamba max, 4035 outrunner. The OEM RC ESC wouldn't stay synched on the hills, but I think it might have been a bad cell in the battery pack. I will retest it tomorrow and see what is up.

Final speed about 10mph last I tested. Runtime is about a mile on 2 amp hours so far, but with a new cell that will probably improve. It has a ton of torque, the motor is rated 4hp continuous and 5000w peak.


I have to be careful, it likes to wheelie with the seat so far back.

Here she is

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I ruined a mamba max during today's test. I also tried out the OEM RC ESC and it wouldn't keep sync under load. Still worked well if I didn't goose it too fast. The mamba max wasn't even hot, kinda strange that it bit the dust although not a complete surprise.

John! Dude! You should be in the Movies!

That was great! Encore Encore.........clap-clap

hehehhe.........Looks like you were having some fun there.

:rofl:Thats the best clown bike Ive ever seen. :lol: I'm still rolling on the floor laughing. Funniest thing Ive seen in a long time. I dont know what I was expecting while I was reading this thead over tha last few weeks, but that was not it!!!!:tongue:

I say you should take the little wheels off of that bike and strap them on a full size bike frame. Of course it should still be pink. :whistle:



Nice work man! Looks like a great contraption for hurting yourself. :mdr:

More Power!!!

That was hilarious! Too bad my bike won't be so much fun...

My next build will keep the rear wheel size (easier to get the right rollout) and have a 20" front. Like a chopper. I will have to mig a frame up, so it will really be a custom motorcycle when I am done.

Thanks for the comments, it is pretty fun to ride :D Maybe a bit dangerous.

JRH is single-handedly redifining how we see transportation.

I can see the future now, middle aged men in business suits riding electric powered little girl bikes to work!

Seriously dude, that was funny, especially the music, and the bright yellow vest. Can't wait to see the "chopper" bike, that should be interesting!

Bravo Bravo.
 

I must say even though your test was not a huge breakthrough in electical science it was a smashing success in humor. A wheelie dumping you off would have been better though. No really even though things did not go exactly as you expected there has to be some amount of humility during any testing phase of operations. I think you are at the very least having fun and learning from the experience. I would love to see a 60 to 75 lb kid drive that thing. I bet it would do much better for them. No pun intended. The thing that is cool is that you have a good number of others here on the site thinking about giving it a go and try their own version. I know I am thinking of trying something like this now. I am just recovering custody of my three young children (9,11,& 12) after 6 years, and the two boys would have a blast working with me on something like this. There are so many options and different ways to go that you could spend years testing and having fun along the way. Still our hearts are truly in the RC arena. Good luck with your future testing and keep feeding us with the comedy shows. That was really funny.:lol:

Got version two done. Now I will make a new tranny to double the geardown, and then I will double my voltage on the motor. This should keep wheelspeed the same while halving amp draw assuming I don't goose the throttle more on startup.


I may change the gearbox to include a clutch so that the motor can start up with no load. This will keep me from having to push off on start. So far, I have logged about 20 miles on the new frame. A 6 mile trip costs me a whopping $0.0138 in electricity assuming 10% charger inefficiency. Version three is in the works, I am converting my santa cruz bullet to a pedal/electric motorcycle. Version four is also in the works with a very high power system. Most likely a 90v 200a ESC and matching motor.


This thing is so much fun, I can't believe it took me so long to get it done. I will be selling gearboxes in the future most likely.

nice!!! you should get the Hobby city 80-100 outrunner

No need, mine produces 3500w