Electric bike build

[Fallenleopard]

Okay so me and some friends are in a school vs school sort of competition where you have to make an electric bike.
just wondering if anyone could help us with some ideas maybe put us on the right track. we are going to use a bike because they have good wheel bearings and will have nice speed.

here are some of the critera it has to fit.

-must be able to reach 40km/h
-must be able to do a lap of the track with an average speed higher than 30km/h
-total battery cost nust only be $200 au (all batterys have to be new)
- person to complete most laps wins!

those are the main ones that we are trying to work out
we are in australia so would prefer links to anything from australia although i would appreciate anyones comments or ideas we are not sure what size motor to use on the bike because you have to keep that speed and do alot of laps so we need time and speed. we are also allowed to use forms of regeneration on the bike. also we were thinking SLA batterys but we need to get the right voltage

so if anyone has any ideas then thanks!

i have already read the post on electric stuff but i need some ideas for this particular project

Thanks!

 

[Badot]

-must be able to reach 40km/h
-must be able to do a lap of the track with an average speed higher than 30km/h
-total battery cost nust only be $200 au (all batterys have to be new)
- person to complete most laps wins!

So as long as it's capable of going 40k, and 30k around the track, aside from that you can go any speed you want?

Also, any restriction on pedal power?

If you're going for the most laps you'll probably just want to slowly putz around the track to minimize air resistance. And/or look into fairings. Then get a small guy in tight cycling clothes to ride it, and have him hunch forward the whole time. Air resistance is where most of the energy put into bikes goes. Obviously you'll want to minimize friction too though. Starting off with a 700c bike, or some kind of road bike in general helps a good bit over mountain bikes.

Aside from that, your #1 thing will probably be finding the cheapest bang for your buck in batteries, and the most efficient motor you can find.

 

[DaiSan76]

What about using some of these? They are light and give good power.

http://www.nitrorcx.com/98p-40c-10000-2s2p-hardcase.html

 

[Badot]

Lead acid is probably the way to go...

This is cheaper, and will give you a boatload more power: http://www.allelectronics.com/make-a-store/item/GC-217/12V-18AH-SEALED-LEAD-ACID-BATTERY/1.html

Weight isn't really an issue so long as you don't need much acceleration and you're not braking much. It'll add a slight rolling resistance, but it's fairly negligible.

Now, pushing the rules here probably but: is there anything saying you can't use a gas engine to drive an alternator which powers an electric motor? And in addition to a basic electric bike setup, pedal power the wheels or an alternator to power the motor?

 

[nak18]

Lead acid is probably the way to go...

This is cheaper, and will give you a boatload more power: http://www.allelectronics.com/make-a-store/item/GC-217/12V-18AH-SEALED-LEAD-ACID-BATTERY/1.html

Weight isn't really an issue so long as you don't need much acceleration and you're not braking much. It'll add a slight rolling resistance, but it's fairly negligible.

Now, pushing the rules here probably but: is there anything saying you can't use a gas engine to drive an alternator which powers an electric motor? And in addition to a basic electric bike setup, pedal power the wheels or an alternator to power the motor?

This is wrong on so many levels. Weight, power, discharge.

Power: 12v x 18A = 216W, which is only going to move a object with around 250lbs about 10mph. This is only if gearing is right. Most motors are 24v-48v, requiring 2-4 lead batteries

Weight: Person ways 100lb, bike 30lbs, and electronics 100lb.
He's going to need more the one battery as above .

Discharge: Don't spend $200 on Lead batteries when all their going to do is loss capacity after your drain them out.

--------------------------------------
My idea:

Use Lipo battery, brushless R/C motor.

This motor is equivelant to 3hp when running at max speed.
http://www.hobbyking.com/hobbyking/...SK3_6354_215kv_Brushless_Outrunner_Motor.html

All you have to do is match battery to motor rating.

5 in series and 5 in parrallel, should be enough to get you atleast 10min. Through in 5 more if the budget allows.
http://www.hobbyking.com/hobbyking/store/__16482__ZIPPY_Flightmax_2650mAh_2S1P_45C.html

 

[Badot]

This is wrong on so many levels. Weight, power, discharge.

Power: 12v x 18A = 216W, which is only going to move a object with around 250lbs about 10mph. This is only if gearing is right. Most motors are 24v-48v, requiring 2-4 lead batteries

Okay, really, where the **** is this stuff coming from?

First of all, the battery I linked to is $53. Let's assume he uses 4. 12v x 18ah x 4 = 864 wh.

Your battery? You can get 16 of them for the same price. 7.4v x 2.65ah x 16 = 313.76 wh. Seriously, one of these packs has the equivelant power of 5 good alkaline AA batteries.

Second -- Weight and input power have ABSOLUTELY NOTHING to do with top speed alone. It takes a combination of input power, aerodynamics, and rolling resistance to determine your top speed, and weight and input power to determine acceleration.

Third, you've shown a very distinct lack of knowledge on batteries -- there's a very common thing called deep cycle lead acid batteries which are specifically made to be run down to 20-30% and charged back up. The one I linked is one of them, it was originally meant to be used as a battery backup to a security system. Either way, a regulator could be extremely easily constructed to stop current draw below a certain voltage to prevent this.

Fourth, The total wattage of the batteries has NOTHING to do with how much power they can put out at any given time. Batteries are rated by amp-hour, meaning over the course of one hour they can output the given amperage, and then be dead. If you draw twice as much, it lasts half as long. Extremely basic math there. Why do you think a digital thermometer running on a single AAA battery can last years, but when you put one of those fancy 'high capacity' batteries you linked to into an RC plane it only lasts for 10 minutes?

It takes more than learning how to do basic electrical math from a wikipedia article to understand how batteries work. Please don't run around telling people they're wrong when you can't even get your own sh*t straight.

 

[nak18]

Okay, really, where the **** is this stuff coming from?

First of all, the battery I linked to is $53. Let's assume he uses 4. 12v x 18ah x 4 = 864 wh.

Your battery? You can get 16 of them for the same price. 7.4v x 2.65ah x 16 = 313.76 wh. Seriously, one of these packs has the equivelant power of 5 good alkaline AA batteries.

Second -- Weight and input power have ABSOLUTELY NOTHING to do with top speed alone. It takes a combination of input power, aerodynamics, and rolling resistance to determine your top speed, and weight and input power to determine acceleration.



Third, you've shown a very distinct lack of knowledge on batteries -- there's a very common thing called deep cycle lead acid batteries which are specifically made to be run down to 20-30% and charged back up. The one I linked is one of them, it was originally meant to be used as a battery backup to a security system. Either way, a regulator could be extremely easily constructed to stop current draw below a certain voltage to prevent this.

Fourth, The total wattage of the batteries has NOTHING to do with how much power they can put out at any given time. Batteries are rated by amp-hour, meaning over the course of one hour they can output the given amperage, and then be dead. If you draw twice as much, it lasts half as long. Extremely basic math there. Why do you think a digital thermometer running on a single AAA battery can last years, but when you put one of those fancy 'high capacity' batteries you linked to into an RC plane it only lasts for 10 minutes?

It takes more than learning how to do basic electrical math from a wikipedia article to understand how batteries work. Please don't run around telling people they're wrong when you can't even get your own sh*t straight.

Woah, Buddy, are you mad?

1) The motor take 10s lipo thats 37v, lets use your scenario.
I have 16 lipo batteries.
5 in series gives me 37v and 11 in parallel 29.15A
37v*29.15A =1078.55W

The lead batter you choose scenario:
4 batteries, 3 in series 36v and 1 in parallel 18A
36v*18A= 648W

You could under power the motor, but then you have to take in consideration of the rpm.


2) If he has 4 sealed batteries and 100lb person on his bike how hard would it be for him to accelerate at standstill. The cranks will probably be removed since the lead batteries will be in the way and that means he's going to have to push it like a motorcycle going in reverse.
If he uses anything other than a BMX or Trial bike he has the potential to fall in turns, because batteries will sit higher near the top tube.

3) My lack in knowledge. You showed your battery having about 900w and the motor is going to want to pull 2kw. You didn't even take the battery configuration properly.
How low can you run the one in the picture? If its around 30-40% he's going to get there fast which ever battery he chooses, because the strain its going to have pushing that weigh.

4) Take your advice on Amps, look at the "C" of Lipos. Hobbyking, is a USA/HK company with no real competitors. I think valuepartz.com or whatever its called had 4s lipo@ 5A for $12.

I could get on some of most of the stuff you said was stupid, but I'm going to stop at. The reason those high fancy batteries last 10mins, is because of weight. You won't fit 12lipo in a small R/C, because they're replicas of the real design scaled down. If you want the time to run it for 1A, than buy the extra batteries duh. Wait,then the controller and motor heating issue comes in.

Yea, if you would have done you wiring correct you would have seen that trying to prove me wrong wasn't even worth it. When your back at the start, of finding batteries to supply the Watts for my motor.


And you should have said

"Why do you think the batteries in a hotwheels car last longer, atleast it on topic. The mottr in those cars are 100-300W. If I put a lipo in a thermometer, bye bye battery change.
Have a nice day.

 

[Badot]

Woah, Buddy, are you mad?

1) The motor take 10s lipo thats 37v, lets use your scenario.
I have 16 lipo batteries.
5 in series gives me 37v and 11 in parallel 29.15A
37v*29.15A =1078.55W

Okay, basic math time again. 5 seriex x 11 parallel = 55 batteries, running you over $710 to get a slight improvement over $200 worth of lead acid.

You could under power the motor, but then you have to take in consideration of the rpm.

I never said a thing about that motor, nor did the OP. I'll be the first to admit that I don't have a large amount of experience with electric motors, HOWEVER a motor designed for high draw and short runtime like that is bound to be less efficient than one designed for a long range light weight electric vehicle.

2) If he has 4 sealed batteries and 100lb person on his bike how hard would it be for him to accelerate at standstill. The cranks will probably be removed since the lead batteries will be in the way and that means he's going to have to push it like a motorcycle going in reverse.
If he uses anything other than a BMX or Trial bike he has the potential to fall in turns, because batteries will sit higher near the top tube.

There are no required acceleration specs, for one. Furthermore, if you had even looked at the battery I had linked to, it is 3" wide. It'll probably fit inside the cranks of 99% of all bicycles. Even then, there's nothing saying the OP will not choose to use a rack mount or a tandem bicycle. The bike will handle exactly the same way in turns, bicycles DO NOT support lateral loads through turns, they lean, meaning it will handle in the exact same way, just requiring a tad bit more countersteering. Either way, the weight of those batteries is fairly negligible compared to the rider.

3) My lack in knowledge. You showed your battery having about 900w and the motor is going to want to pull 2kw. You didn't even take the battery configuration properly.
How low can you run the one in the picture? If its around 30-40% he's going to get there fast which ever battery he chooses, because the strain its going to have pushing that weigh.

A 900 watt-hour battery set with a 2000 watt draw will last .45 hours. Again, incredibly basic math.
Furthermore, I showed your batteries to provide about 300 watts max for $200. That's with 16 of them, so you can't even run them in an even 5 series to match the voltage of the motor properly.

Yea, if you would have done you wiring correct you would have seen that trying to prove me wrong wasn't even worth it. When your back at the start, of finding batteries to supply the Watts for my motor.

Please provide sources proving what I am saying to be wrong.

 

[nak18]

Okay, basic math time again. 5 seriex x 11 parallel = 55 batteries, running you over $710 to get a slight improvement over $200 worth of lead acid.



I never said a thing about that motor, nor did the OP. I'll be the first to admit that I don't have a large amount of experience with electric motors, HOWEVER a motor designed for high draw and short runtime like that is bound to be less efficient than one designed for a long range light weight electric vehicle.




There are no required acceleration specs, for one. Furthermore, if you had even looked at the battery I had linked to, it is 3" wide. It'll probably fit inside the cranks of 99% of all bicycles. Even then, there's nothing saying the OP will not choose to use a rack mount or a tandem bicycle. The bike will handle exactly the same way in turns, bicycles DO NOT support lateral loads through turns, they lean, meaning it will handle in the exact same way, just requiring a tad bit more countersteering. Either way, the weight of those batteries is fairly negligible compared to the rider.



A 900 watt-hour battery set with a 2000 watt draw will last .45 hours. Again, incredibly basic math.
Furthermore, I showed your batteries to provide about 300 watts max for $200. That's with 16 of them, so you can't even run them in an even 5 series to match the voltage of the motor properly.




Please provide sources proving what I am saying to be wrong.

UNDERSTAND THIS FIRST
===================
A lipo pack is 3.7v, but if the pack says 2S1P than its 7.4v at the same amps as before.
If its 1S2P than its 3.7v but with double the voltage.

The battery, I shown was 2S1P, which mean its 3.7v x 2 = 7.4v. Now if you add 5 in series that 7.4v x 5 = 37v. Now if you have 11 batteries in parellel at 2.65A than the total will be 29.15. After you get the watts the total is 1078.55W. Check your math exactly. 1078W/2100W= 0.513333Hours. So that 30mins. He's doing a race so, it will be about 10minutes average 15minutes top.

This should explain why you only need 16 batteries.
Note: He's not going to see 2,100W more likely 1,900W. 2100 is the max, and you should run anything near the max unless you plan to replace it.


What I type before, I realised you didn't understand lipo's and what I was saying that much.
==========================================
1) You are not making since. Where are 55 batteries come from?
5 in series and 11 in parallel.
That's a total of 16 batteries. You don't put 11 batteries to every one battery in series.

I'm not in the mood to go into exact detail to all your answers, so here is a video of a gokart running, 3 turnigy motors(5kw each)with a total of 22 batteries. He's supplying 50v at 22A for 8mintues for a 15kW system. The motor I posted was 2kw which consumes 7 times less battery power than this setup which uses the same amount of amps.

You keep saying I'm wrong and my basic math is wrong then here goes a gokart proving me right. Unless this cart is running on nuclear fusion or miracles.

http://www.youtube.com/watch?v=vwODx028_Jw

As you can see
==============
55mph is pretty fast for 22 batteries that have amps lower than the one I posted.

----------------------------------

Here's a few sources that can help my statements:
1)http://endless-sphere.com/forums/viewtopic.php?f=6&t=8482
2)http://www.youtube.com/watch?v=61sM9qovORU
-5km is 3miles, which is usually 12 laps around a school track.
-If he uses the batteries I linked to, then he only needs 5 batteries.(Amazing right.)
3)http://stealthelectricbikesusa.com/the-bikes.html
Battery Capacity : 1.1kWh, my batteries were 1078W.
-Look they're using Lipo's, too and there selling them.

I think I was able to prove my point.


When you said it will fit in 99% of bicycle cranks, it made you sound like you don't know what bicycle are. If you can put a lead battey inside a bike crank then you should patent it. Last time I checked cranks are less than 2inches in diameter.
We don't know the gearing or his motor choice so all we really are talking about is the batteries.

=====================================
At the end Lipo batteries are cheaper for the power. If he choose to draw the samee amount of power as your lead batteries he'll out perform them.

 

[jman231994]

Im in the same team as fallen leopard...some of our funnier ideas have been: Using electricity to drive electrolysis and running an engine on hydrogen

Buying 200 dollars worth of lemons

Or as someone said...a generator haha

I agree with the lipo ideas, except we need a motor that is efficient at pumping out the power we need, I've seen a 5300watt brushless on hobbyking but its probably going to draw more amps than is necessary and useful. Also our average speed around the circuit has to be 30 kph, otherwise we need to make it up by lowering our times later on. The circuit is on a slight slope, so we can sort of coast for the first half and climb for the second.

The LiPo idea is great, except for the wattage and voltage. We want at least 24V which means a decent array of 2S lipos or 2 3S would probably be close enough...and then wed need to build up the Amp Hours to something useable...If any of you can do some calculations to tell us something good for this and under 200 AUD then please feel free

Thanks

 

[Badot]

1) You are not making since. Where are 55 batteries come from?
5 in series and 11 in parallel.
That's a total of 16 batteries. You don't put 11 batteries to every one battery in series.

http://www.otherpower.com/otherpower_battery_wiring.html

Read. Understand. Do the general public a favor.
If you have 5 of those batteries in series you get a big pack at 37 volts, 2.6 amp hours.

1 battery x 5

If you have two of those big packs in parallel, you get 37 volts, 5.2 amp hours.

1 battery x 5 x 2.

And you want to run a 5x11 cluster, for 5x the voltage, 11x the amperage. 5x11=55.

As absolute proof, your math violates the law of thermodynamics. 1 battery pack = 7.4 volts x 2.65 amp hours, or 19.61 watts. 16 of them (19.61x16) is 313.76 watts, like I had previously stated. 55 of these batteries (19.61x55) is 1078.55 watts, what you claim to be able to get from 16 of them.

When you said it will fit in 99% of bicycle cranks, it made you sound like you don't know what bicycle are. ... Last time I checked cranks are less than 2inches in diameter.

Last time I checked cranks are usually made of solid metal and around .5" diameter, although not necessarily round. Are you, by chance, referring to the frame tubing?

By 'inside the cranks' I mean it will have a narrow enough profile on the frame to allow the cranks to pass on either side of it so it would not interfere with pedaling, like you had originally said they would.

 

[nak18]

http://www.otherpower.com/otherpower_battery_wiring.html

Read. Understand. Do the general public a favor.
If you have 5 of those batteries in series you get a big pack at 37 volts, 2.6 amp hours.

1 battery x 5

If you have two of those big packs in parallel, you get 37 volts, 5.2 amp hours.

1 battery x 5 x 2.

And you want to run a 5x11 cluster, for 5x the voltage, 11x the amperage. 5x11=55.

As absolute proof, your math violates the law of thermodynamics. 1 battery pack = 7.4 volts x 2.65 amp hours, or 19.61 watts. 16 of them (19.61x16) is 313.76 watts, like I had previously stated. 55 of these batteries (19.61x55) is 1078.55 watts, what you claim to be able to get from 16 of them.




Last time I checked cranks are usually made of solid metal and around .5" diameter, although not necessarily round. Are you, by chance, referring to the frame tubing?

By 'inside the cranks' I mean it will have a narrow enough profile on the frame to allow the cranks to pass on either side of it so it would not interfere with pedaling, like you had originally said they would.

OH ok, thanks for helping understand that. hahaha, learned something new today.

I did a research on the battery you choose, looked at the reviews and the battery is rated on a 5hr discharge, so that is 18/5 = 3.6A/hr

Seeing that the OP doesn't need 36v, but 24v and wants about 40kph, it shouldn't be that hard to find batteries. To meet the standards he wants for 24v system

BTW here are some lipo batteries that are 4s(14.8v) and are 5A/hr.
http://www.ebay.com/itm/TRANSMEIIC-lipo-battery-5000mAh-14-8V-XT60-Connector-/110746052526

Doing my math right.
2 in series = 29.6V
4in parallel = 20A
total = 592W

14.8*5*8= 592W

Max discharge is 592*20C= 11.84KW


592/2100=0.28. -> .28 *60=16.8 Mins
40kph to mph = 24mph/60= 0.4mi * 16 = 6.4 miles rounded to 6 mi. * 4 = 24laps

So if the trackis is 1/4 of a mile it will be able to do 24laps at 40kph for a duration of 16 minutes. That's in a controlled environment though.


What bike have you chosen?
What is the overall budget?
What is the motor budget?
-Have you considered hub motors.
Did you take into consideration of customs on foreign parts and calculate shipping price/time?

@ badot
By cranks I thought you were referring to the round hollow cranks. Some new modern bikes have hollow crank arms to reduced weight. They are usually tampered, though.

 

[jman231994]

Sorry neither of us have posted on here in a while.....your saga of disagreement got a tad boring.

Anyway, what we are entering in is not a straight out race but an endurance competition. i.e. most laps done whilst still beating a certain lap time.

And whilst I know if I was somebody else reading this I would definitely want to know all of the details, I don't think I should give them up just yet because odds are another team has been checking out this forum for help. Some of the other teams are using 36v....whilst I agree this is better for performance and a little bit on current draw, I think that the extra cost needed to buy 3 batteries rather than 2 certainly outweighs the gains. Not to mention we would be sacrificing run time not cost due to the battery cap of $200.

I will say that the frame is a steel frame due to our lack of skill when it comes to aluminium welding. We have also extended the frame for comfort reasons

And because Australia is awesome....We dont have to pay import duties or customs costs as long as its less than $1000 hehe

And there isnt really a budget....I will say that our motor was quite expensive.....I will probably post some pics the day before scrutineering or something so we cant get copied......That Is All....Thanks

 

[fowler]

id be using one of those inner hub motors with lithium ion batterys

we had to do a similar thing in school but made a trike

top speed was about 36 and we got 1 hr of use with 2 12v motorcycle batterys

but the team with lithiam ion batterys ran outta time at 3 HOURS!!! and they were still going strong

 

[jman231994]

Awesome fowler....what Ah were your moto batteries? I wish we could get lithium ion's but 200 bucks is a bit short.....The concept of hub motors is good. But I like a bit more control.....GEARS

 

[fowler]

The maximum battery bank storage is 432 Watt-hours. This
equates to 72 Ah at nominal 6V, 36 Ah at nominal 12V, 24 Ah at
nominal 18V, 18 Ah at nominal 24V, or 12 Ah at nominal 36V.
this is the site http://evchallenge.org.au/Ev_Challenge/Home.html

come to think of it
we had 3 12v baterys in our later karts

i wasnt there for the electrics though i was there as an aluminium welder fabricator

 

[nak18]

id be using one of those inner hub motors with lithium ion batterys

we had to do a similar thing in school but made a trike

top speed was about 36 and we got 1 hr of use with 2 12v motorcycle batterys

but the team with lithiam ion batterys ran outta time at 3 HOURS!!! and they were still going strong

3hrs is amazing, do you know the battery setup and there top speed?

 

[fowler]

there top speed was also about 36

but on our course we hardly used it as it was a tight course in a car park

we all had regenerative brakeing as well

but as i said i wasnt there for the electronics and i dont really understand it

this team wasnt a school team they were a university that enterd so there budget would have been much bigger

 

[jman231994]

The rules for that one are really different to ours...better in some ways...harder in others.

For instance, we need to have a minimum 1200mm eye height....So either a high chair go kart....a really tall guy or a bike. Doesnt really leave much for the imagination. (except the high chair go kart)

Ours is on the Newcastle Kart Racing Club's circuit. Which is quite interesting....hills

Also...Any tips on welding aluminium with a mig welder.....It takes me half an hour to prepare a piece just to get an average weld....any less and i get an almost completely seperate bead?


Thanks guys

 

[fowler]

ya u gotta get it super clean

we had a speicial wire brush that was for ally only
also it goes without saying we had ally wire and straight argon

i cant say i got much more than average welds but they were stronger that the metal

the heat affected zone around the weld was an issue
on the first kart i had a couple of peices break about 4mm from the weld

end result i welded like i was trying to make a bad steel weld lower amps higher wire speed
seemed to work
but on this scale i cant really judge if it was a good weld it looked ok and non broke after that

your rules are quite differant
our top speed isnt quite your minimum
what is your time limit