Electric Scooter Project

[Johnny Ohm]

Im hoping to mod my old razor scooter (remember when those were cool?). What i want to do is power it with an electric motor powered off a car battery. Assuming the battery is 12V, does anyone have any suggestions on a motor I could use? Im about 200 or so lbs and Im hoping to reach 15-20 miles per hour (sorry to anyone who uses the metric system).

Any comments would be greatly appreciated,
JΩ

 

[rjvh]

Car battery would not be the best choice I think
they're good for delivering a high peak but havin a steady draw you better can use golf car batterys or electric wheel chair batterys

no you have also the answer for your motor

the ones in a wheelchair are probably smaller and easyer for you to build in

the speed is all about gearing and the state of the battery

Robert-Jan

 

[The Mad Professor]

Sorry but I cannot quite get my aged brain around the mechanics of fitting a car battery to a 'Razor' scooter. Where to put your feet is kinda of important to the design.

The E100 and E300 versions use Ni-Cad batteries with a motor sourced from the R/C model world. You could try beefing up the power pack for extended range, or carry a spare charged one.

The only variant that would be large enough to carry a lead-acid battery would be the 'Pocket Mod Bike' and that is already a purpose built electric scooter...

 

[Willbe]

use golf car batterys or electric wheel chair batterys

Deep cycle batteries.

How steep are the hills you want to climb? That will determine the peak torque required for a 200# payload.
For max speed, I'd look at power specs for existing scooters that advertise 20 mph. I think the drag increases as speed^2.
How long at what speed will give your battery A-h requirements.

 

[Super_voip]

Try bicycle to electric bicycle kits found on eBay, that should provide a good starting point. The big problem with them is the price.

 

[rjvh]

Try bicycle to electric bicycle kits found on eBay, that should provide a good starting point. The big problem with them is the price.

That's always the case with deep cycle batterys

Robert-Jan

 

[Johnny Ohm]

Thanks for all the help!

I looked on ebay for the electric bicycle kits and I wouldn't say they are out of my price range... but Im hoping such an expense can be avoided. These kits come with extras such as mounting hardware, front wheel, etc. that I wouldn't need for this project.

Does anyone know where I could buy some deep cycle batteries and a 500+ Watt motor sold seperately from a kit?

@Willbe: I found some info for a "Goped" scooter which is capable of reaching 20mph. The site says the scooter runs of a 24V motor powered by 4 12V sealed lead acid batteries. The transmission is a "Chain Drive - 15/76 stock sprocket ratio".

Im going to use the scooter mostly around my college campus and town which is mainly flatland, so I dont think the torque requirements will be that great. Also im hoping to avoid too much complication regarding the transmission, the goped comes with a computerized transmission and speed controller which i feel is unnecessary for my needs.

Thanks again,
JΩ

 

[Willbe]

"the goped comes with a computerized transmission and speed controller which i feel is unnecessary for my needs. "

It's necessary, otherwise they wouldn't use it.

First, figure out how much your spare time is worth and how much of it you would probably spend in making this thing.
Here's one way to approach this.

I flip a coin; heads-you build it, tails-you buy it.

How little would these scooters have to be selling for, for it to make absolutely no difference to you which way the coin landed?

Would you accept a job at those per-hour wages?

Anyway,

look up the energy density best suited for your constraints to pick your battery technology

try these guys for batteries
**broken link removed**

and a junk yard for a DC generator which you might be able to use as a ~half-kilowatt motor.

With enormous effort you might get half the performance of the commercially made scooters; the manufacturers have brought a lot of resources to bear when they designed these things and they buy parts in lots of 1000's or 10,000's.

On the other hand, if you build it, the lessons you learn vs. the "tuition" you pay for those lessons might be quite a bargain.

 

[blueroomelectronics]

Reminds me of the many UPS posts that pop up from time to time. You CAN buy a UPS for far less than building one from scratch.

If you need something then it's often just better to buy it.
If you'd like to learn something it'll often wind up costing more than just buying it outright (unless you have the parts & experience already)

I always like how when something is not understood (or expensive) it's often considered an expendable (or unnecessary) part

There were some fellows built their own Segway, cost them $4,000 and it "sort of works" but they're students and are on to version 2 (and more money of course)
**broken link removed**

 

[Johnny Ohm]

Long story short, Im a freshman in college hoping to become an EE, and I am doing this project primarily for the making rather than for the owning of the product. I also understand that the performance of the scooter will be affected due to the fact that it is DIY instead of being mass produced.

If I wanted to buy one, I would have. And if cost were an issue why would I buy an expensive scooter rather than just walk the < 2 miles to school?

Also, the goped comes with two modes, economy and full power. Unless my understanding of electronics is as elementary as blueroomelectronics is implying, this capability is what the speed controller is used for. Im hoping to utilize the KISS (keep it simple stupid) policy and bypass the controller. I want two modes: On and off. If I do actually need the part, I would appreciate any and all help.

Thanks Willbe for the battery supplier, and are you talking about a starting motor?

 

[blueroomelectronics]

I did not mean to imply you have limited knowledge, far from it. I was simply pointing out that if it's a learning project then have at it.
Knowledge gained from experimentation is priceless, well worth the effort.

The gripe was aimed at the posters who want it done for them, lock stock & barrel. The truly funny ones can't even get the parts required and it's not for learning but the hopes it can be done cheaper with parts found at the local Radio Shack and/or scrapyard, old TV etc.
The reference was meant as a generalization of something that is all too common IMO, I myself when studying a project am most interested in the parts of the circuit I don't fully understand. Others (the UPS crowd for example) want to omit pretty much everything as it's either not cheap or seems too complex.

PS look how complex the Seqway is compared to the above photo. When designing a product you have to plan for abuse and overdesign or you'll be fixing the things instead of making money.
**broken link removed**

 

[Oznog]

Well, you try to connect that batt to the motor without a speed controller- like just a relay or knife switch- and you're gonna have hell to pay. The starting torque of a DC motor on a big batt is enormous. It can easily break traction, skid, and generally hurt you and be dangerous.

You need a gel cell/AGM batt. There's actually quite a lot of difference in them, and you have specific needs. Unfortunately mfgs are rarely forthcoming in the strengths and weaknesses of their design.

The one I DO know about is BB Battery's EB series (Electric Bike), because one of their engineers took the time to explain everything in proper electrical terms that I have confidence in. Their EVP series for example has super-high current capabilities but wears down sooner over many deep cycles- including the high current capabilities. You'd only need current this high for racing anyways. The EB was designed to deliver high currents (though less than the EVP) over as many cycles as possible in high temp/vibration environments.

Digikey carries the best price on EB batts. I went to some work getting them to carry the EB20-12 as a "stocked" item because the Robomower community desperately needed a battery that wasn't going to crap out in a season. Actually, right there, 2x or probably 4x of these will do it for you. But, it WILL be expensive. However, be aware that other batteries costing half as much will probably not give you anywhere near half the total runtime hours, nor the range-per-charge, making them a less economical option unless you want to just run this a few hours and take it apart again.

 

[Willbe]

Thanks Willbe for the battery supplier, and are you talking about a starting motor?

I think a starter motor takes 70A, no load, and it sounds terrible spinning this fast.
I'm hoping a junked auto DC generator used as a motor is a little more suited to this app..

BTW, a guy in grad school made a go-kart powered by several car batteries in series and a starter motor. He put one of the batteries in backwards and it violently objected to that treatment.
Of course, he wore the same shirt he was wearing that day, now with little holes and stains all over it, to class.

 

[Johnny Ohm]

@blueroomelectronics: Thanks for explaining, I understand where your coming from, I did a bit of perusing and I found your comments to be pretty accurate.

@Oznog: Ill look on digikey for the batts. It sounds like your speaking from experience, thanks for the tip.

@Willbe: nice story, I hear chicks dig scars, even if they are caused by a DIY gokart accident. And sorry for the misunderstanding, I hoped you werent talking about a starter motor, my buddy suggested it and I was hoping he wasnt right.

Anybody else have any imput on the battery? right now I like the AGM battery that Oznog suggested.

Also, can anybody send me a link or make a quick sketch of how a speed controller circuit would look? I really dont need much complexity.

 

[nickelflippr]

Anybody else have any imput on the battery? right now I like the AGM battery that Oznog suggested.

Supposedly there are only a few manufacturers of the AGM style batteries, like US and East Penn being a couple. So you may very well see a similar battery that Oznog suggested with a different name like MK or Deka. If you can't compare or find the data sheets or manual on the battery then don't buy it. Only suggesting this in order that you may be able to defer shipping charges?

Have a 12V 100AH AGM (Deka) in the camper and its been great. The battery only dropped a couple tenths of volt after sitting idle for 3 or 4 months, so believe what they say about the self discharge rate.

To charge the AGM/VRLA type battery, get a 3 stage type charger that has an AGM setting. The AGM battery will have a different charging requirement than the flooded lead acid type, so be sure the float charge is below the mfg. data sheet recommendation. If you boil the AGM battery, there is no putting the fluid back in.

That GOPED motor looks to be a highly modified wheelchair motor. The direct drive gearbox ones like an Invacare will top out at about 5-6 mph. If you could find a junk motorized wheel chair, you might find many of the parts that you would need. I've seen some wheel chair motors with pulleys, which could be real handy.

 

[Johnny Ohm]

Im starting my search for a motor and battery but it may take me a little while. Until then Im hoping to get some imput on a simple speed controller, I dont think a pre-programed computerized controller is necessary, but ive been told a simple knife switch or an on/off toggle switch will work very well.

Could the speed be controlled with little more than a 555 timer and a variable resistor?

Any and all imput is greatly appreciated.

 

[rjvh]

Im starting my search for a motor and battery but it may take me a little while. Until then Im hoping to get some imput on a simple speed controller, I dont think a pre-programed computerized controller is necessary, but ive been told a simple knife switch or an on/off toggle switch will work very well.

Could the speed be controlled with little more than a 555 timer and a variable resistor?

Any and all imput is greatly appreciated.

That little more should be your power mosfets in parralell to control the motor

the 555 could deliver a puls that also could be made variable duty cycly with a variable resistor so I don't see the problem in that

Robert-Jan

 

[Willbe]

No resistors; watt-hours are at a premium here.

 

[3v0]

No resistors; watt-hours are at a premium here.

I think he means that the resistor will control the duty cycle of the PWM generated by the 555. The current it draws is so very tiny that it does not matter.

EDIT:
But I would dump the 555 and put in a PIC with an tach and accelerometer. Fly by wire... Regenerative breaking and and a solid state beverage cooler and you are set

 

[Johnny Ohm]

No resistors; watt-hours are at a premium here.

Im planning on using the variable resistor in conjunction with the 555 timer to increase the duty cycle, increasing the speed of the motor. Ive heard about designs which use variable resistors alone to reduce the power and I agree that reducing the power in this manner is unacceptable. Thanks for the concern.

@3v0: My knowledge of PICs is pretty limited. Could briefly explain how the circuit looks and/or make me a quick sketch? Ill look into that cooler idea