The 12 volt bike to end all 12 volt bikes

[creativeadapter1990]

I am contemplating building a low voltage lead acid bike that will be capable of running with the petrol bikes on the blue star/vfw highway (speed limit 65 kilometers per hour, regularly ignored by cars) It will consist of a mountain bike frame, wide medium pressure comfort cruiser tyres and a semi homemade reluctance motor to be made using the stator coils of a 200+ amp truck alternator and a self machined rotor and other parts. Will use well over 2000 watts. A commercial builder has used similar alternators as the basis for cheap multi horsepower reluctance motors with good results. pedals will simply be removed, I am not going to pretend I will be pedaling plus I think pedals on a motorbike look silly, and with this big a motor are not needed.
To feed the massive amp draw for a useful time I intend to use a semi deep cycle Group 31 (I already have 2 of them from my boat project) these weigh about 27 kg and are rated at 12 volts 105 ah. Their low temperature preformance is astounding; at 20 Fahrenheit they are brief burst rated for over 650 amp, continuous rated for 200 amps, and are capable of far more amps at warmer temps.

Homemade and heavily modified motorcycles and kit cars are surprisingly popular local to me so the dmv/rmv will not be a problem, although due to local laws regarding high watt bikes it will be a "limited access vehicle" (more powerful than a moped but not capable of running on the freeway) This means I will need to pay taxes ($60 every other year), get a police officer to assign vin number, buy a license plate, and have a valid and current learners permit or drivers license.

I already have an ebike build under my belt, using a bmc V1 hub motor and a 36 volt 26 ah powersonic lead acid pack. It is ok on a flat but I live on a hill where it slows to little better than a walking pace at full throttle.

does anyone on this forum have experience with reluctance motors, or high watt low voltage systems. Has anyone had that much weight on a bicycle frame (if it matters I am 195 cm tall and weigh over 90 kg) I have considered going with the frame of a small motorcycle for better strength and high speed handling.

 

[TylerDurden]

Please expand on your rationale for using such a low operating voltage.

 

[dogman dan]

I'd build something based on 48v, with motors and controllers similar to golf cart stuff, but able to mount a sprocket.

Seems like at 12v, you'd need wiring the size of garden hose.

 

[creativeadapter1990]

I have a giant 12 volt battery at hand, an alternator to convert, a lathe to make the rotor and other components, too much spare time, a desire to build somethng unusual, and a desire to go fast, and cant justify the cost of a new high voltage battery. the local stores have good prices on 4 gauge cable. another option would be to get a motorcycle frame and put both giant 12 volt batteries in it in series. plus the look on peoples faces when the see a 12 volt bike that isn't some child's toy.

some of it is just to prove a fast low voltage bike can be built and work. I know of a few companies building 10kw+ marine engines using 48 volts, they seem to work fine. a truck alternator will generate 200 to 300 amps and spin at 12000rpm in its original useage, I see little reason why a the same would not take even more amps as a reluctance motor where there is virtually no induction heating of the rotor. I will probably use a controller of about 150 to 250 amps depending on what i can get a good used price on.

also regarding golf cart motors I want there to be a reluctance motor powered bike out there, and Lectra went out of business several years ago.
most of its time would be spent in far more tame places than the vfw highway, I would spend much of my time at a more moderate 25 to 30 mph.

 

[TylerDurden]

24V is a much better option, 36V is even better.

Are these batteries flooded or AGM?

 

[dogman dan]

Nothing wrong with cheap fun with stuff on hand. Just expect a lot of posts soon, saying get a different motor and 72v lipo.

 

[creativeadapter1990]

Thank you dogman.

If I had enough money and the folks at EVionyx would get off their duffs and give us what they promised us by 2007 I would be using a 60 volt 80 ah electrically rechargeable zn air bank that weighed under 30 kg. :x

i cant afford a 72 volt lipo

The real purpose of the project if started would be to make the motor as machine shop skills practice. the bike would be something to do with said motor besides just watch it turn. a lot of amateur machinists build something pretty but useless and rev it up as a very expensive noisemaker at swap meets and tractor shows. i want to make something with a purpose in life and get better at metal working as well as riding around town.

 

[Pure]

I would still go with 12V LiPo over lead acid. Your cost isn't going to be that much (well save for the fact that you already have some Lead) but the weight savings is worth it. LiPo can def handle the Amps you're looking for. There are even some cool vids on here of people cranking cars with small packs of Lipo.

This pack can pull over 200 amps http://www.hobbyking.com/hobbyking/store/__20845__ZIPPY_Flightmax_8000mAh_3S1P_30C_USA_Warehouse_.html Put 3 of them together so you can have some kind of range and possible 720Amps on demand. Realistically you wouldn't want to pull max amps from them but they would more than be able to handle your application. All for less than 150 bucks. Lead really has no place on a bike.

 

[NeilP]

Well I have not read the thread...but if you are going low voltage, but want to go up a bit...36 volts...I have a 350Amp 36-48 volt curtis brushed motor controller for sale in the Used section
If it is any use let me know...I need cash for my 5404 project

 

[Doctorbass]

.. at 12V i would need 1000 amp continuous and 2000amp burst on my giant DH built !!

Doc

 

[amberwolf]

Just so you are aware, lead-acid (LA, SLA, FLA) has a very high Peukert toll on the total capacity (Ah, Wh) it can provide when that is drawn out at very high current (A) rates.

Since you will need to draw it out at many times it's capacity rating (C-rate) at such a low voltage, in order to provide the total power needed for your system, you will essentially be throwing away more than half of your battery pack's capacity via the Peukert effect. Potentially a lot more than half.

Plus the voltage drop on the nominally 13.6V SLA under those loads will further reduce the total power (W) you can actually provide at any one moment.

That is why most people choose a higher voltage. It usually is better to series the batteries you do have (if you have more than one of the same kind) for that higher voltage, especially for chemistries like LA, simply because of the losses to Peukert if for no other reason. Raising the voltage decreases the current necessary, which lowers the C-rate, which lowers the effect Peukert has on the total capacity, sometimes dramatically.


Another reason is the wiring: it would have to be extremely large gauge wire to avoid significant resistive loss in the cabling itself (causing further voltage drop in the system, causing even further power losses before reaching the motor, requiring even higher current draw to achieve the same total motor power).



Based on my own experiences and a few years of reading of various custom-builds for heavy stuff and/or high speeds, I highly recommend you do not use a bicycle frame for it, but rather either a scratch-built frame from heavy-duty materials, or a modified dirtbike or motorcycle frame. Much less flexiness and more durability, less likely to break under load.

 

[dogman dan]

Nobody willing to drive 40 mph here either. 40 mph club is not so extreme for bikes, just extreme for junky wallmart stuff.

 

[ZOMGVTEK]

Unless you want 100W or so, 12V is too damn low.

The lowest I would venture is 6S LiPo, or '24V'... Most 24V controller even have a 10.5V LVC, which works out great on 6S. You buy 6S packs and parallel them until you get the capacity you want, it's stupid easy to make, charge, and maintain. 8S would be a bit better, but a bit harder.

Even at 24V, you are running small stuff hard above about 500W. You'd need a lot of lead to get meanful capacity out. I was getting 4-5AH out of 18AH SLA's when discharged 2-3C peak. And that was with a TON of voltage sag. It's pathetic stuff. I have a 12V 108AH battery on an inverter that nets me about 20AH under 200-300A loading. It's cheap and dumps amps, but you pay the price elsewhere. I have 2' of 1 AWG wire between the battery and inverter that actually gets warm. You don't want to be running 4/0 or something stupid beefy on a bicycle.

 

[neptronix]

OP, in case you haven't got the idea yet, get back to the drawing board for your ideas. There are multiple problems with this idea and i'll summarize: it won't work, and the components will cost you more $ than actually doing it right.

high volts, low amps is absolutely the way to go. You're gonna have to reconsider your budget for this ebike project, and probably start a lot smaller as well.

This is not a cheap hobby. I built my first bike for $700 and that was skimping at every corner. Current bike that does 30-35mph cost me about $1200 to build. You can buy the parts gradually, so that's a plus.. but you're just going to have to make an investment in doing it the right way, lest you waste more $..

 

[Drunkskunk]

Doesn't matter how you get there, but get to high voltage.

Since you have 2 batteries already, you have 24 volts. thats twice as likely to work as 12 volts. That would cut the amp load in half.

Incase you didn't know, watts = Volts X amps.
So 120 volts and 20 amps is 2400 watts
but at 12 volts it takes 200 amps to make 2400 watts.

lead acid batteris don't like to porduce high amps for long. It kills there capacity and shortens their life. Its far better to go high voltage.

 

[AussieJester]

+1 to amberwolfes post, he explained
Best why lead acid has no place on a bicycle
I'm all for DIY, but what your planning won't
Work well, its both a waste of your time and
your resources...imo

KiM

 

[creativeadapter1990]

Re: everyone who said "lead acid doesn't like to pull big amps; put more in series" lead acid doesn't like high C rates.

the group 31 is a very large battery, an equivalent (equal nominal watt hours) 120 volt pack would consist of a 10s pack of 12v 10ah batteries.

pulling 2000 watts from a 12 volt pack means 2000/12 = 167 amps
for a 100 ah nominal battery: c = amps/amp hours = 167/100 = c rate of 1.67

pulling 2000 watts from a 120 volt pack means 2000/120=16.7 amps
but for the same weight and energy density as before the 120 volt pack has only 10ah
c=16.7/10= you guessed it c is 1.67

compare to say an xlyte x5 series with a 48v 18ah sla pack pulling 1600 watts

1600/48= 33 amps
33amp/18ah= c of 1.85

c rates of under 2 are well within the capability of lead acid.
thick wire is cheaper than lipo and isn't all that heavy.

anyway 2000 watts would be at full throttle, I would spend most of my time drawing well under 1000 watts. The ezip 1000 is 36 volts and uses a 10 ah pack for its 1000 watt motor (although strictly limited by controller to about 900 watts at wot)
25 amps and 10 ah makes for a c rate of 2.5
claimed and according to the reviews accurate range is 12 miles.

 

[neptronix]

77lbs to go 12 miles. I can do that with 9lbs of lipo.
You'll need 4-6 gauge wire, and that is indeed heavy.
You will turn tons of power into heat running a high amp setup.
For high amp 12v operation you are probably looking at a 20-30lb industrial machinery type motor.

Even then, 2500w is not motorcycle-competitive power.
So you'll have 100+lbs of junkyard parts on your bike.

Meanwhile other people on the forum are pushing 2000-3000w on motor + battery setups that are 30 pounds or less.

Go put a few boat anchors on your bike before you go on this mission to build the worst electric bike ever. See how it handles. That will give you an approximate idea of how your bike will perform. Make sure to go down some hills while you're at it and learn why heavy bikes are bad news :lol: :lol:

 

[torqueon]

Hey if your really into this 12 volt cheap ride thing. Go pull a starting system off a big block ford motor!! Hook it all up and push the button and go like hell !!! I always wanted to try this LOL !

If you really want to learn how to machine stuff fast and well Get a Job in a machine shop and you will learn !

In all seriousness listen to what these guys are telling you. The people here know there s***

 

[Ricky_nz]

pulling 2000 watts from a 12 volt pack means 2000/12 = 167 amps
for a 100 ah nominal battery: c = amps/amp hours = 167/100 = c rate of 1.67

So What is the capacity of your group 31 battery at the 0.6 Hour rate.
Lead batteries are normally rated at the 20 Hour rate.

 

[neptronix]

Haha... well there is an issue with using starters. They are not rated for high continuous output. They're designed to take hundreds of amps for a very short period of time.

Maybe a starter for a semi truck would work, lol.. run it at 1/3rd it's peak power constant.. it may live.

 

[AussieJester]

Hey if your really into this 12 volt cheap ride thing. Go pull a starting system off a big block ford motor!! Hook it all up and push the button and go like hell !!! I always wanted to try this LOL !

If you really want to learn how to machine stuff fast and well Get a Job in a machine shop and you will learn !

In all seriousness listen to what these guys are telling you. The people here know there s***

There is a video of an Aussie guy on YouTube who has done exactly that (maybe not from a big block ford but was a heafty size starter motor)

The weight of OPs batteries alone is more than my entire drive train AND batteries and then
i still come under 20kilo for all of it, a setup that @ 10 000watts... Wanna use Lead you will be disappointed...

KiM

 

[Ricky_nz]

The starter motor thing works ok for a short period of time but the battery required is big and heavy
Heres a work mates starter motor bike
[youtube]1qonMG_zhsY[/youtube]
Its neat because its so crude but not a reliable system

 

[torqueon]

God I love this forum !! Great Vid !

 

[dogman dan]

Still nothing wrong with it, if he feels like wasting his time. But I would keep total costs down to at most, 50 bucks.

That motor will run on 24v, so at least do that. But the 40 mph club with a 70 pound battery on the bike sounds danm sketchy to me. That is, if his actual real world speed comes even close to that.

If he makes it work, then good on ya mate! But a 5 min ride on any of our track racing bikes would have him going, OHHHHHHH YEAHHHHH! This is much nicer at 120v.