# New build. Kids EV. Lots of questions.



## vlad_t (Jun 22, 2012)

I'm so glad I found this forum!
Please tell me if my project doesn't qualify for this section and need to be an another forum.

Technically, I'm building an EV. But a small one. After wife wanted to buy one of those plastic electric cars for kids for $250 - I saw an opportunity to have a fun project, and decided to build an EV for kids, myself. My kids are currently 3.5 and 1.5.

It's a two seater, side by side, open wheel, rear engine. 4.5 ft long, 3ft wide (at the rear wheels), body is 20" wide. Body built out of plywood, with oak for structural reinforcment, glued+screwed together. No separate frame. It's very strong and rigid back to front (can easily carry my 150lbs mother-in-law, but not too rigid on twisting which is fine. Rear wheels are 15"x6x6 wheels, and fronts are slim 12" bicycle wheels.

Anyway, I currently have a rolling chassis and working on finishing steering. Can take pictures if somebody interested. 

I need some advice (a lot of it) on electrical setup. My target speed for two kids in a car - about 10mph. If I'll need more, I can always change sprokets later, but say 10mph is target speed, considering kids age. The chassis weight is about 50lbs now (wild guess), two kids are around ~65lbs together.

I'm not too strong in electrical area. After reading a lot, I guess I need 24V system, with may be 350W motor. That is my wild guess. I'm afraid it can be too much for 10mph. I don't really need a racing speeds. But then I'm really afraid to spend all the money and have some slow thing neighbourhs will laugh at, and not able to climb a driveway (about 10deg incline).

Can guys who have experience in such things, tell me what setup I likely need to get 150 lbs at 10 mph top, be able to climb 10deg, and accelerate reasonably well?

For the controllers and accelerator pedal I found this site:
http://www.electricscooterparts.com/throttlesstandard.html
and I really hope this pedal will work with one of their inexpensive controllers:









Can somebody advice if those controllers are any good/will work for my project? And which one exactly? Reverse ability would be good, but minimally I just need it to work with gas pedal, and charge.
http://www.electricscooterparts.com/speedcontrollers24volt.html

What about motors? May be I just need 100W instead of 350W? How do I know what I need to get 150lbs to 10mph without killing it?
http://www.electricscooterparts.com/motors24volt.html

What about batteries? All I need is half an hour from this thing. Hour would be nice. What would be the cheapest and lightest setup for, say $100?
I have one good PC 545 laying around. If I buy another one like that, will it do? Or will it kill them because they are wrong type? 

Thanks a lot,
Vlad


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## vlad_t (Jun 22, 2012)

a few pictures.

very beginning:









current state:









engine bay, for engine, disk brake, and ideally, battery(s):


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## Woodsmith (Jun 5, 2008)

Welcome to the forum. It looks like a nice little project for your kid there.

The 350W motor will be good and fairly powerful for your kids and you can limit the speed by changing the sprocket size and/or limiting the controller. 

It is difficult to say if 100W would be enough, maybe but also maybe no fun for the kids if there is a slope or a bump to drive over. It depends on the rolling resistance of the kart.

The components you link to look like fairly low cost electric bicycle parts and that seems like a good start. 
Batteries may not be too big an issue. My tractor uses four Optima Red top batteries found in a junk yard and are more then enough for a period of 'playing around' with logs. They are 50Ah gel batteries on near half a ton of tractor pulling logs.

Anyway, I am supposed to be building a similar sized little kart to entertain my Dad (he is nearly 80) and I am planning on a 200W motor as I have one spare. No idea if it will be enough but if it is powerful enough for a bicycle up to 15mph it will do for my Dad.

I look forward to your progress.


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## skooler (Mar 26, 2011)

Hi Vlad,

Before my RX8 conversion, In my early teens. I built an electric scooter/Bike capable of about 20MPH and 4 Miles range.

I went for a 36V system using an unknown controller and 3* 12V, 20AH Lead Acid batteries and a 800w motor.

I think that a similar setup would be more than capable of moving your cart around.

You may want to consider using a controller capable of around 30-50Amps to have enough torque for your incline.

I'd go for a 24V, 500w controller at the very least.

Perhaps buying a controller that is slightly more capable than you require so that you can potentially add more batteries (and speed) as your kids get older? It also means that you wont be pushing it to its limits as often for the sake of a few $$.

Hope this helps,

Cheers,

Mike


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## vlad_t (Jun 22, 2012)

Thanks, guys.

So currently I'm thinking to go with this. All controllers in the price range I like seem to be 30amps. Is it not enough? I really like being able to have reverse, brake lights and motor cutoff during braking on that controller!:

*24 Volt 250 Watt Electric Scooter Motor*
24VDC 250W electric scooter motor. Powerful four brush permanent magnet electric motor design with 100% ball bearing construction. Includes 11 tooth sprocket for #25 chain. 15" long power leads with 1/4" push-in connectors. Shaft rotation reversible by reversing power leads. Dimensions: 4" wide x 3-1/4" long excluding shaft, 4-1/4" long including shaft. Mounting bracket measures 4-1/4" x 2-1/8 with 4 threaded mounting holes. Weight 4.3 lbs.
Item # MOT-MX350B

*24V 500W Speed Controller With Reverse* 
Reversible speed controller operates in either forward or reverse mode.  Designed for 24 Volt motors up to 500 Watts. Maximum current 30 Amps. Under Voltage protection 20.5 Volts. Current limiting feature prevents controller and motor damage due to over-current conditions. Under voltage protection feature prevents over-discharge and extends battery life. Uses standard 3-wire variable speed hall-effect throttle. Fits many common electric scooter and bicycle models. 
Item # SPD-24500R


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## Caps18 (Jun 8, 2008)

I tried to build one of those when I was 8 or 9. It didn't get very far. Hopefully this current EV build that I am doing goes better.


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## vlad_t (Jun 22, 2012)

Logged in to ask more questions on my new project (in another thread) and find out that I have an old thread here.

Just to finish it here's pictures of my little roadster for the kids - 24v 250w motor, one wheel drive, speeds up to 15mph. Surprisingly good handling

I went a little overboard with decorations, it was fun


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## veverone (6 mo ago)

Wow! The car looks absolutely amazing! I know it has been a long time, but do you have a comprehensive list of parts and sizes and are you willing to share? Still... even the images are a very very good source of inspiration. thank you!


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## MarkDoronin (8 mo ago)

yes, perhaps this is a car from my childhood!


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