Electric bike power

[johnrobholmes]

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 ) 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.

[sikeston34m]

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.

[johnrobholmes]

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.

[johnrobholmes]

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

[MetalMan]

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.

[johnrobholmes]

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

[sikeston34m]

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

[johnrobholmes]

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!

[BL_RV0]

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

[Serum]

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?

[Patrick]

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.

[johnrobholmes]

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.

[crazyjr]

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

[Patrick]

Originally Posted by crazyjr

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.

[MetalMan]

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?