# Motor power/ battery capacity ratio?



## elevatorguy (Jul 26, 2007)

Dan Yanoff said:


> Hi everybody! This is my first post here, but I'm also a member at a "smoking" car forum - canadiandriver dot ca.
> 
> I always wanted to ride or drive something cool and environmentally friendly. I am still stuck with a conventional car for work but I am planning to build an EV for shopping and other short distance chores.
> I am starting low and my first project is gonna be a bicycle conversion. I think I will go with wilderness energy's 36 v brushless motor but I want to use a bigger battery than in the kit. There are good SLA batteries made for main power use which are 12v 28Ah. 3 of them will weigh 33 kg. Do you guys think its an overkill for a 600 watt motor?
> ...


Dan,
It really depends on the range you want, I use 18 ah batteries and can ride for about an hour at 20mph. I am not too familiar with the kit you are going to use, but if the battery weight is up high on the bike the center of gravity may become a problem.
More capacity wont be overkill, but depending on desired range you may be hauling a lot of weight that you dont need to.
Jerry


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## Dan Yanoff (Jan 18, 2008)

Thanks, Jerry. The kit I'm planning to use is this: 
http://www.wildernessenergy.com/product_info.php?cPath=24&products_id=30

If the motor is REALLY 600watt it translates in 0.8 HP which is pretty good IMO even with 33 kg of battery weight. When I was a kid I had a gas moped rated 1 HP, and even though it only had 1 speed and a huge heavy frame I was quite happy with its performance on paved surfaces. 
To be on a safe side I'm thinking to order it with a 24" wheel which should give me a little more torque. 
It is still way too cold here. In spring I will try to find out if a local supplier got such a kit installed and possibly take it for a test ride. I'm just curious about its acceleration and how powerful it feels.


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## BenNelson (Jul 27, 2007)

I built a 36V electric bike from a hub motor kit.

I am using 18AH batteries and have decided it is overkill.

That 20 mile range is about right with that size battery. The trouble is that it's a bit extra weight when you are just under pedal power without the electric.

I think I would use maybe 12AH batts. Just remember, if you run out of juice, you can still use your legs!

Electric Bikes may be the only hybrid vehicle that really makes sense.


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## Dan Yanoff (Jan 18, 2008)

Which kit did you use and how quick does the bike accelerate to max speed? 

Thanks.


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## BenNelson (Jul 27, 2007)

I used a Golden Motor hub kit.
I think they were a little cheaper when I bought mine than they are now.

I would put my bike in lowest gear to pull away from a stop, pedal about two full turns, then put it in highest gear and start to pedal and hit the throttle all the way up.

Doing this seemed to minimize the amps to pull away from a stop.

I could go from a stop to 20 MPH in about 5 seconds.

Acceleration is not a problem. Besides, what's the big rush? You are on a bike, enjoy it!


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## Dan Yanoff (Jan 18, 2008)

Thanks for the link. Acceleration in itself doesnt matter to me of course, but it relates to how brisk the bike will be up hill. When I build one there is a park I have between my place and the office with one steep hill so it would be good to know as well if there is a hub I can get in Canada with possibly more than 600 watts output. I dont really care if it will be street or sidewalk legal or not, I just dont see cops charging (no pun) me for having an EV


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## BenNelson (Jul 27, 2007)

One thing I really like about a front-hub electric bike is that it's a simple human-electric hybrid vehicle.

I have one huge hill by my house that would not be climbable on electric, but I would have to walk up it rather than pedal.

With both pedals and electric together, I can make it up that mountain without stopping, although it is pretty slow.

Also, if you ever run out of batteries, you can still just pedal away.

It sure has plenty of torque. One time I decided to pull away from a stop without pedaling, just to see how much power it had. The front wheel ripped itself loose and shot forward without me!


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## Dan Yanoff (Jan 18, 2008)

" It sure has plenty of torque. One time I decided to pull away from a stop without pedaling, just to see how much power it had. The front wheel ripped itself loose and shot forward without me!"

Forgot on of these


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## xrotaryguy (Jul 26, 2007)

I only have a 300w motor on my bike and it does just fine. the only hills I pull with it are little ramps up to freeway pedestrian bridges, canal bridges, etc, but it handles those very well. I pull my son on his trailer bike much of the time too. It is very satisfying to cruise right past a fellow cyclist while pulling a 6 year old.


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## Mastiff (Jan 11, 2008)

This website offers bicycle kits of all kinds:
http://www.beepscom.com/category_s/276.htm

If you want to keep a lower center of gravity, just get a welder and some small steel rod or tube and build off the back end of the bike two hanging battery spaces and stuff your batteries down into it to get them lower.

If you build it right you can set two 12v batteries into the side slings and one where the water bottle usually goes between the frame. (giving you 36 volts)

I think a hub motor might be the best because it requires the least modification to your bike and allows you to still easily pedal to assist the motor.


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