# Plans for my e-bike Help Needed!



## gtdave (Dec 9, 2009)

Hi everyone,

Im fairly new to this whole concept but have always wanted to have a go at building one. It will be based around a Mid-range full suspension downhill mountain bike. I was planning on having the motor set up as direct drive to a sprocket mounted to the disc mounts on the rear wheel, and running a hydraulic rim brake on the back end, and also still keeping the normal cranks and gearing to allow for human power aswell. thus allowing me to freewheel while the motor is engaged. 

I am also thinking of converting a high ampage car alternator into a motor for use as they are small in size, fairly lightweight, extremely cheap to source, powerful, and more reliable than a motor i would be able to source for a similar price.

Was thinking of a 48V 100-200A system possibly with 4 battery packs in series, was thinking of using 12V 72Ah gel batteries, which are fairly small and lightweight and easy enough to mount on a bicycle.

The only problem I can see would be the speed controller, would I have to build my own speed controller for use with an alternator or are there suitable ones out there quite cheap which could deal with the sort of power and ampage I am wanting to use. This build is going to be on a tight budget, so anything I can source cheaply will be good. 

I am also in the UK, so websites with parts would have to be UK based to avoid high shipping costs.

Just had a thought, would I be able to use a 24V drill motor, and the speed controls from a drill to run the bike? would it have enough torque? I know the RPM's would be awesome though.


----------



## order99 (Sep 8, 2008)

I haven't put my bike together yet either-still in the 'picking the right frame from Goodwill' mode -but i'll volunteer my thimbleful of knowledge anyway...

Ebay is a pretty decent source for the low-end controllers. I picked up a 12-40V 30A controller minus frills(no case) for $22 after S&H. You can score some neat DC motors there as well if you have some patience.

Drill motors are high RPM and decent torque for what they're made for, but they aren't really designed for continuous usage. I suspect that one would overheat pretty quickly-on the other hand, if you have some cheap, used drills you don't want anymore you haven't invested much if it does blow...i've actually seen a bike on Youtube run this way using an entire drill and adapter-the drills gearing offset the RPM problem, but I don't know what kind of endurance the setup had.

I'm currently playing around with PM motors from radiators myself. I don't know how one will fare on my bike yet, but they seem to have a bit of torque to them, overvolt to 24V with little heat buildup and were designed to last a long, long time. If they don't work on my bike I might make a DC-powered lathe and refurbish some broken power tools to run on a 12V deep cycle...

Alternators are AC motors and require a different type of controller-both the rotor and stator need current, plus you have to control the frequency as well as the voltage. There aren't many AC controllers around, they're expensive and I don't know enough to say if one would work with an alternator-in theory, i'd say they would. Do you have an electronics background? If so, you might be able to DIY a controller-I know I couldn't.

Here's a discussion on alternators as motors, both in AC mode and a PMDC conversion:

http://www.rcgroups.com/forums/showthread.php?t=905411

Here's the best place I know to check out DIY electric bikes of all varieties-I think there are a few Alternator motors in the mix somewhere:

http://endless-sphere.com/forums/index.php

So what gear ratio were you planning for the direct drive? Also, 72Ahr sounds like a really long-range battery-what kind of weight are we talking about?


----------



## mxmtech (Apr 21, 2009)

27 miles is a long way



> Was thinking of a 48V 100-200A system possibly with 4 battery packs in series, was thinking of using 12V 72Ah gel batteries, which are fairly small and lightweight and easy enough to mount on a bicycle.


Sounds like about 300 pounds of batteries, impossible to mount on a bike. Bicycle wheels absolutely will not carry the weight.


----------



## gtdave (Dec 9, 2009)

They are actually small and lightweight batteries. They are designed for use in motorbikes, and quadbikes, they are sealed gel units which is way safer than Lead Acid units, and weigh a lot less. I have just re-checked on the batteries, and they are actually 17Ah each, not 72Ah, the ones that appeared to be 72Ah were actually 7.2Ah but mispelled in the title on ebay....lol.

I don't have a background in electronics, but I am very good with electrics, and have worked with PCB boards quite a lot. I do also modify xbox360 motherboards to cure overheating problems, so I am fairly confident with messing about with electronics.

I was thinking of doing the PMDC conversion, but I would of thought just removing the diodes and voltage regulator from the alternator would allow it to be used as a motor, but obviously it would need a low voltage through the coils first to allow it to spin up.

I am planning on going around some breakers yards in a couple of weeks to look for an alternator to use, can pick them up extremely cheap, approx £8 - 10. The cheapest DC motor I have seen is a 450w motor on ebay for £35, and this motor would not be powerful enough for what I am wanting to achieve.

Just spotted this AC controller on ebay, would this be suitable for controlling an alternator with diodes, and regulator removed?? 

http://cgi.ebay.co.uk/24V120A-AC-Sp..._Control_ET?hash=item22fdb5aa49#ht_1051wt_732


----------



## ev_nred (Sep 23, 2009)

gtdave said:


> Hi everyone,
> 
> Im fairly new to this whole concept but have always wanted to have a go at building one. It will be based around a Mid-range full suspension downhill mountain bike. I was planning on having the motor set up as direct drive to a sprocket mounted to the disc mounts on the rear wheel, and running a hydraulic rim brake on the back end, and also still keeping the normal cranks and gearing to allow for human power aswell. thus allowing me to freewheel while the motor is engaged.
> 
> ...


soundas to me like your doing a moutian bike to dirt bike am I rigth? if so are you alaowoed to use it on any trails thta dirt bikes can go on? srroy for takeing up you time! thank you in advance ! oh and whats your buget? i'd say thta with $800 you could get 70-90 km of range. but I am no expert


----------



## gtdave (Dec 9, 2009)

I will be converting a Downhill Mountain Bike ( Full suspension approx 6-8" travel front and rear ) into a Human/Electric Hybrid. I will therefore be able to use it on all the local mountain bike trails, and in parks etc, as it is still classed as a mountain bike, that has electrical assistance. 

I used to race Downhill Mountain Bikes, so I am wanting a machine capable of having as much fun going up the hills as coming down them, and Im not into cross country riding, so not too keen on pedalling back up hill. 

So in essence it is sort of a Dirt bike build, but a more subtle one....lol

My budget is very limited, as I am seeing if this is possible to do on as small a budget as possible then if it works, I can upgrade parts as I go along.

I have a question for the tech-heads. If I use an alternator, could I use a Diode Bridge to convert it to DC and then use a PWM controller, I have a couple of circuit diagrams for making a PWM controller, and also a Diode Bridge to convert AC to DC, any help would be massively appreciated....Going alternator hunting in a couple of weeks....I cant wait!


----------



## ev_nred (Sep 23, 2009)

gtdave said:


> I will be converting a Downhill Mountain Bike ( Full suspension approx 6-8" travel front and rear ) into a Human/Electric Hybrid. I will therefore be able to use it on all the local mountain bike trails, and in parks etc, as it is still classed as a mountain bike, that has electrical assistance.
> 
> I used to race Downhill Mountain Bikes, so I am wanting a machine capable of having as much fun going up the hills as coming down them, and Im not into cross country riding, so not too keen on pedalling back up hill.
> 
> ...


 srroy for this post but I migth ask if you were to remove the pedals it will be allowed on dirt bike trails rigth? (I am thinke this would be cool and may make a trike verison) thanks!


----------



## Amberwolf (May 29, 2009)

You might want to take a look at my bike project blog in my signature, as it is one of the ultimate no-budget conversions.  

Remember that 4 of those 17Ah SLAs will be at least 60 pounds, not counting whatever battery box you use, which must be quite sturdy to handle the remaining travel of bumps left after the suspension dampens them, with all that mass in there. 

SLA's do not weigh much different than regular fluid-filled lead-acids for the relative power you get from them, as they are still lead-based. Make sure that you are not getting "starter" batteries, as they are not designed for deep cycle use and will die quickly if used that way. Go for the types designed for wheelchair or powerchair use, as those *are* designed for deep cycle use and will last a little longer (200 to 500 charge/discharge cycles, depending on your usage, so up to a year or more, if not abused, but typically less than a year if discharged heavily most of the time). 

Also, SLAs or any lead chemistry pays a high toll to the Peukert effect, which means that the faster you take power out the less of it you get in total. Given your intended use on hills, I'm going to say that 17Ah will end up more like 8Ah actual power output, depending on actual current draw. 


You will use a lot of power going up hills, and even more with those heavy batteries on it, so they will not give you much range. Pushing them till they're totally dead (80% DoD) on my bike, with 36V 17Ah, gives me about 19 miles range, with the last two miles almost completely pedal-power. That's with a 360 pound load, including me, the bike, and cargo, at roughly 35Wh/mile, on nearly flat roads the whole way.

With any significant hills (steep and/or long) I would probably get 1/3 of that at best, due to the weight, probably less. 

I am building a Li-Ion pack of some 300 18650 2Ah cells that will end up giving me aboutg 36V 60Ah, and will only weigh 2/3 of what my SLA pack does. That will give me at least 5 times the range, though it will not perform as well for high-current draws as the SLA (which can produce up to at least 105 amps for the 17Ah batteries I have, for a short burst before controller currentlimiting kicks in). There are Li-Ion cells that *can* deliver much more (liek A123 in DeWalt packs) but they are much more expensive.


You may want to ensure you have good steel rims and hubs and good stainless steel spokes on the bike. DON'T use aluminum hubs or rims with that kind of weight on there; based on my experiences they'll just break with any kind of abuse. (there might be aluminum stuff that *will* work, but it will almost certainly cost significantly more or be thicker/heavier to the point that good steel ones would be cheaper and of the same or lighter weight). 


There is another forum, Endless Sphere, which is almost exclusively ebikes of various kinds, with lots of very very good information. I suggest you also check it out as well as what is on this forum. There is a specific thread there about battery boxes, with pictures and whatnot, including a few that use the size batteries you describe.


As for the alternator, while you can use a diode bridge to take the OUTPUT of an alternator and turn it into DC, you cannot use one to take DC from a PWM controller INTO the alternator and make it work. You CAN make the alternator into a BLDC motor, using one of several DIY methods I've seen scattered around the web, and use a BLDC controller. 

How powerful it ends up will partly depend on what magnets you end up installing, and partly on whether you rewind it or not, and what kind of alternator it started out as. 


If you end up buying a controller rather than building one, check out 4QD, as their controllers are made for heavy-duty use on golf carts and whatnot. Their 2QD which is sometimes available works well for my CrazyBike2, driving a wheelchair motor/gearbox that then drives the regular shiftable bike drivetrain. 

If you build your own, stock up on MOSFETs and driver transistors and gate resistors, as you will probably toast a few in the design and testing phase.  I have a little box of fried ones from my experiments. 
________
Asian live


----------



## Amberwolf (May 29, 2009)

gtdave said:


> Just had a thought, would I be able to use a 24V drill motor, and the speed controls from a drill to run the bike? would it have enough torque? I know the RPM's would be awesome though.


If you use a sufficient gear ratio to change the high RPM to low RPM and high torque, then you can even use a drill to move a car (slowly). It has been done. 
________
WEB SHOWS


----------



## fleebell (Jan 5, 2010)

gtdave said:


> They are actually small and lightweight batteries. They are designed for use in motorbikes, and quadbikes, they are sealed gel units which is way safer than Lead Acid units, and weigh a lot less. I have just re-checked on the batteries, and they are actually 17Ah each, not 72Ah, the ones that appeared to be 72Ah were actually 7.2Ah but mispelled in the title on ebay....lol.
> 
> I don't have a background in electronics, but I am very good with electrics, and have worked with PCB boards quite a lot. I do also modify xbox360 motherboards to cure overheating problems, so I am fairly confident with messing about with electronics.
> 
> ...



You might want to look up some of the rc radio 3 phase controllers too. Some of them can carry quite a bit of amperage and voltage.
Lee


----------



## Amberwolf (May 29, 2009)

fleebell said:


> You might want to look up some of the rc radio 3 phase controllers too. Some of them can carry quite a bit of amperage and voltage.


Though often not for more than a few minutes of high power use at a time, as they typically don't have a good way of getting rid of the heat build up in the switching devices.  There is at least one good discussion about that on the Endless Sphere forums, if I can find the link to it.
________
BONG


----------



## sunworksco (Sep 8, 2008)

www.astroflight.com


----------

