Trying to plan out first build

[TRIGON391]

Just started reading about ebikes and I definitely want to try to make one myself. I'm 18 and it would be perfect for getting to places around a college campus next year for cheap. I was initially planning something very ambitious, an RC drive with lipos and all that, but realized I should "walk before I run" and start out with a hub motor setup. My budget for this project is roughly $1000. If I could get it under 1000 with reasonable reliability, that would be great. On the other hand, if I need to spend more than 1000 to get the real world performance I want, I can but I really want to keep it under 1000 if at all possible.

So far, I have determined for sure that I want to base the build on a BMX bike, probably a cheap steel BMX bike from walmart or craigslist. I want to use a BMX bike because they're compact, easy to transport, and wouldn't be too difficult to carry up a flight of stairs if I had to. The lack of suspension also doesn't bother me I just want to get from point A to point B on electricity comfort will be a secondary consideration. I definitely want to use a rear wheel drive setup due to its obvious advantages over a frontwheel setup.

In terms of performance, I want something that can go 30mph with no pedaling on flat ground with decent hill climbing capabilities. When it comes to range, 20 miles with no pedaling would be ideal, but I would be content with a 15 mile range without pedaling for the time being because I can always upgrade my battery setup. I'm in very good physical shape, so I'll also be pedaling a lot which I understand will help out my range, but I still want at the very least a 15 mile range with no pedaling. And I guess another factor that would have an effect on the performance is the fact that I'm a pretty small person, my weight fluctuates from 130-150 (thanks to wrestling).

I'm confident in my abilities to put the bike together myself, I've been tinkering with stuff ever since I was a little kid and I have a lot of experience with soldering and electrical projects, and I have no problems reading up on things and overcoming problems by myself.

So based on my requirements and the research I have done, it seems like I should be looking into direct drive hub motors. I prefer direct drive over geared because geared hub motors have more moving parts and less upgrade potential. In terms of batteries, I'm leaning towards lithium ion or lifepo4. Lipos are an attractive option but they are obviously a bit risky to use and don't last for as many charge cycles as lion or lifepo4.

Are my expectations for performance realistic based on my budget and small size? If yes, what combination of parts or complete kit should I get that will give me that kind of performance? If my expectations aren't realistic, how much more will I have to spend so that I can get the performance I want?

Oh and I live in the US on the East coast if that helps at all.

Thanks for any help, I'll definitely try to give back to the community and document my build on this forum.

 

[dogman dan]

Well, not as unrealistic as some. Others want 30 mph for 60 miles, and cheap, and light enough to carry up stairs.

You'll need a faster winding, in a presumably 20" wheel. The standard windings when put into a 20" wheel will torque up real nice, but not reach 30 mph on 48v. So a lot will run them at 72v. That's real fun and all, but starts complicating that goal of simple basic transport. One great source of motors that are well matched for thier rim size is Grin Cyclery. A 9c kit might not be the cheapest option out there, but it's a good place to start your ebike adventures. You'll get a vital ebike tool in the kit, a cycleanalyst.

But other cheaper vendors exist, just make sure that you get a faster winding when you order a 20" wheel if you want fast top speed.

A 48v 15 ah pingbattery would give you the range you need. But it might be very hard to fit a battery that size into a bmx frame triangle, and you really don't want to carry it on a rear rack. If you could live with more like 10 mile range, you could perhaps cram an A123 battery from Emissions Free into that frame.

If anything, the bmx frame is the problem, if you want really long range. A regular MTB frame would carry more battery much better, and likely be more comfy on a long ride.

Good thing you are a teen, and old fart like me would die riding 20 miles on a bmx at 30 mph. For you it should be only mildly uncomfortable.

The bmx frame is not a shitty idea, 20" wheels work great on hubmotors. But you might rethink the long range, and just carry a few miles worth of battery. Occasionally, an additional battery can be carried in a backpack for longer rides.

The budget is not too far off, but somehow most of us end up $1200 to $1500 into it by the time we are done. Accessories like big racks, panniers, a nicer bike to start, or longer range expensive batteries. But you can do a smaller range bike for a thou for sure.

 

[dogman dan]

Well, not as unrealistic as some. Others want 30 mph for 60 miles, and cheap, and light enough to carry up stairs.

You'll need a faster winding, in a presumably 20" wheel. The standard windings when put into a 20" wheel will torque up real nice, but not reach 30 mph on 48v. So a lot will run them at 72v. That's real fun and all, but starts complicating that goal of simple basic transport. One great source of motors that are well matched for thier rim size is Grin Cyclery. A 9c kit might not be the cheapest option out there, but it's a good place to start your ebike adventures. You'll get a vital ebike tool in the kit, a cycleanalyst.

But other cheaper vendors exist, just make sure that you get a faster winding when you order a 20" wheel if you want fast top speed.

A 48v 15 ah pingbattery would give you the range you need. But it might be very hard to fit a battery that size into a bmx frame triangle, and you really don't want to carry it on a rear rack. If you could live with more like 10 mile range, you could perhaps cram an A123 battery from Emissions Free into that frame.

If anything, the bmx frame is the problem, if you want really long range. A regular MTB frame would carry more battery much better, and likely be more comfy on a long ride.

Good thing you are a teen, and old fart like me would die riding 20 miles on a bmx at 30 mph. For you it should be only mildly uncomfortable.

The bmx frame is not a shitty idea, 20" wheels work great on hubmotors. But you might rethink the long range, and just carry a few miles worth of battery. Occasionally, an additional battery can be carried in a backpack for longer rides.

The budget is not too far off, but somehow most of us end up $1200 to $1500 into it by the time we are done. Accessories like big racks, panniers, a nicer bike to start, or longer range expensive batteries. But you can do a smaller range bike for a thou for sure.

 

[TRIGON391]

Thanks for the reply, I was hoping I didn't sound too ignorant with my expectations and whatnot, glad to see it might be possible to stay close to my budget. It sounds like the bmx frame is somewhat of a limiting factor. Keeping all other things the same, how much more realistic are my goals on a mountain bike frame instead of a bmx frame? If I were to go with a mountain bike I would get the genesis v2100 from walmart which seems pretty popular on these boards, the size would be inconvenient but not a deal breaker if it is going to make everything else easier.

 

[Brentis]

Welcome aboard the Sphere.

Very well composed first post. Nice to see not all 18 year old' are, let say, challenged. :wink:
I agree with Dogman. I think you have it nailed.
Take a look at my Ghetto build in sig.
I wanted exactly what you wanted. I missed my top speed by a lil', but it throws balls.
Even @ only 1500w.
I am a broken record and recommend Cell_man for batteries & motors. Also consider Grin or Methods as they are continental. :wink:
That said, I think given your past electrical experience, & your willingness to learn, & the confidence you exude, dont fear Lipo.
Its not evil. The user is. If you treat it right, the risks are low.
So Hobby King

Ask questions before buying, it will save you $. and

Good luck

 

[docnjoj]

Hey TRIGON391

Here is an interesting upgrade for Genesis bikes. I hope this helps.

http://endless-sphere.com/forums/viewtopic.php?f=31&t=34939

otherDoc

 

[Brentis]

Here is some of that evil Lipo. Meet LFP.
[youtube]dree0rTr1HM[/youtube]
Dont do that & you'll be 99% kool. :wink:

 

[TRIGON391]

Alright so I did a little more reading based on what you guys have told me and this is what I've come up with so far.
Assuming I stick with the BMX plan, this kit seems pretty good
-crystalyte HS3548 in a 20 inch rear wheel
-20A infinion controller (is 20A enough?)
-throttle
-cycle analyst

all for $620 on ebikes.ca

As for the battery, it seems like lipo might actually be a decent option after reading through a couple more threads, but how exactly should I go about configuring them? It seems like there are almost an infinite amount of combinations of lipo packs that I could get from hobby king that would get me the performance I want, but I don't know how exactly I should go about choosing them.

As far as mounting the battery, I'm willing to get creative to mount it on the bmx frame. I was thinking of sticking them in some PVC pipe or a PVC rain gutter type tube like some other people on this forum have done. I could mount a few of the batteries within the frame and whatever doesn't fit there I can strap on top of it somehow or even just carry the extra batteries in a backpack (although lipos strapped to my back still kind of scare me).

 

[Brentis]

Alright so I did a little more reading based on what you guys have told me and this is what I've come up with so far.
Assuming I stick with the BMX plan, this kit seems pretty good
-crystalyte HS3548 in a 20 inch rear wheel
-20A infinion controller (is 20A enough?)
-throttle
-cycle analyst

all for $620 on ebikes.ca

As for the battery, it seems like lipo might actually be a decent option after reading through a couple more threads, but how exactly should I go about configuring them? It seems like there are almost an infinite amount of combinations of lipo packs that I could get from hobby king that would get me the performance I want, but I don't know how exactly I should go about choosing them.

As far as mounting the battery, I'm willing to get creative to mount it on the bmx frame. I was thinking of sticking them in some PVC pipe or a PVC rain gutter type tube like some other people on this forum have done. I could mount a few of the batteries within the frame and whatever doesn't fit there I can strap on top of it somehow or even just carry the extra batteries in a backpack (although lipos strapped to my back still kind of scare me).

That winding the 3548 will want a few more amps.
Go for the 40amp, its a valuable investment.
You will soon outgrow 20 amps.
+1 on ebikes.ca & a C.A.

 

[TRIGON391]

Alright here's the new complete parts list:

From ebikes.ca
-infineon 36-72v 40A controller 175.00
-crystalyte 3548 in 20 inch wheel 395.00
-throttle 20.00
-cycle analyst with spedo 125.00
so that's $814.00 with shipping so far

from hobbyking:
- 8 x 5000mAh 4s1p 14.8v 20c lipo (http://www.hobbyking.com/hobbyking/store/__15521__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack.html)
and that comes out to $253.01 with shipping

So thats 1067.01 without a bike or a charger so far.

As I understand it, I can connect 4 of the 14.8v lipos in series for a 59.2v 5000mAh pack and connect two of those together in parallel to get a 59.2v 10Ah battery.

According to the simulator on ebikes.ca, this setup would give me 10mi no with no pedaling at 34.4mph. At 75% throttle I would get 15mi at 28.1mph which is a good enough cruising speed for me because I won't have suspension and it'll leave me some extra power for climbing hills if I need it. The only variables I wasn't sure about for these results are the internal resistance of my battery and the full weight of my bike. I left the internal resistance at 0.2ohms but I have no idea what the actual internal resistance of my particular pack would be. I also estimated the weight at 220 lbs which I know will be heavier but it will only perform better than these results if it's lighter (140 lbs for me leaves 80 for the bike and I'm sure it will be lighter than that).

That leaves the bike and a charger. The bike will be the best bmx bike I can find for my needs at around 100$ and I am not quite sure what to do about the charger. My understanding is that it would take at least a 4s charger to charge one of my batteries(one individual 5000mah lipo), so I could just get one or two cheap chargers like that and charge all the individual packs till I can afford more/better chargers.I guess it would work and it's a spot where I can cut a little bit of cost out of the bike without sacrificing performance or reliability, it's just inconvenient to me. So if that means a $50 charger would work, the grand total would be roughly $1217.01, not too bad, but realistically I'll probably be spending another 50-100 for things like the battery mount or lights and stuff like that.

So right now it seems like I can pretty much meet my performance requirements with about $1400 and I leave myself a little space for upgrading, especially when it comes to range (if I can figure out a good way to fit all the batteries on it).

At this point I just need to know if there are any problems with this build that will prevent it from working. Also, how accurate are the graphs created by the ebikes.ca simulator in relation to real world performance?

 

[mvly]

Make sure when you calculate the range, you only put 80% of your lipo capacity. Lipo does not last long if you fully charge it and fully discharge it. Put in 8ah and see what your range is.

 

[TRIGON391]

Thanks for the tip with 8Ah instead of 10Ah and all other variables the same, the new top speeds are pretty much the same and range has gone down to 8 mi at 100% and 12 at 75%. Still acceptable and I'll probably buy more batteries as soon as I have enough money anyway.

 

[Venus]

I have built a BMX with the HS3548, 40amp 12S 10ah lipo setup from ebikes.ca

You will need to widen the rear axle space from 110mm to 135mm...make sure you get a steel frame.

48 kmh is really fast on a BMX with shitty rim brakes. I see no reason to go faster. It is also hard not to stand out (I am 6', 190lbs) so I hope you are not going for stealth.

Otherwise, I am very happy with it so far...

 

[wesnewell]

For $1400 I could build 2 bikes just like the one I have now with upgraded 72V 40A controller. And that includes everything. Bikes motor kit, batteries, extras, the whole works. But hey I'm 65 and 275lbs. WTF do I know.

 

[Beachcruzer]

That is going to be a very badass little bike.

You can charge all your batteries at once by paralleling them, with something like an iCharger 106B. You can even balance charge like that with a cheap adapter that runs six balance leads into one. Read up on how to do it on the forum, or go the smart/easy route and hit up IceCube57 for all the beta and a custom harness. It'll cost you less than buying all the stuff you need to make your own. Either way, budget another hundy for your harness.

My only other input is to think about how you're really going to use this bike. You've specced it as a super fun, high-performance ride. With 40 amps and that little 20-inch wheel, it's gonna rip your nuts off if you're not careful. That pack you're planning will be 66 volts hot off the charger, so your max speed will actually be in the high 30s. By the time it gets down to the 59 volt nominal voltage it's pretty much time to go home and recharge.

So far so good. But then the other part of your wish-list is that you want to ride it 15 or 20 miles. If you want to commute to class or go get groceries, etc., I'd say you'd be better off with a Craigslist mountain bike that'll be way more comfortable and sensible. If fun is higher on your priority list than sensible, by all means go with the BMX.

 

[dogman dan]

I tend to agree with that. Though the bmx will be one fun to ride little beast, It will be a bit hard to carry a large battery all the time and have a really practical bike for 20 mile distances. More can be put in a pack for occasional longer rides though, as I said before.

Nothing wrong with the little bmx though, for the young elastic lower back and knees, and you should be able to cram 8 hardpacks into and along the top of the frame with no problems. So if 8-10 mile range is good enough most of the time, go for it. You can ride 15 mph, and go 20 miles if you must, but it will be hard to hold back and ride that slow once you have tasted 30 mph.

If at some point, you change your mind, and want to go to a 26" bike with suspension, all you will really need to buy is a spoke set and a rim, or perhaps a cheap 26" dd motor only in 26".

You'll have to spread the drops on a bmx, so get steel so you can safely bend it out, and a single speed freewheel. Once you have the freewheel on the motor, you can see what your actual spacing needs to be. You may need to adjust a spacer washer, or even cut a new axle shoulder on the motor, so you can run a spacing less than 135 mm. 135 would be for a seven speed freewheel, and your bmx won't have a derailur.

The other option is no chain, and run a 110 mm front hub on the rear of a bmx frame.

Lastly, torque arms or torque plates. You need em. If the bmx bike has a big enough steel dropout, mabye you can just do this on one side.

Edit. well one or two more last things. You are in the USA, so be sure to order your lipo from the USA warehouse if possible, for quicker delivery, and easier return if you get a stinker pack. Do NOT under any circumstances order any out of stock item from HK.

You will need some kind of charger, so EP Buddy is your buddy. You can get a reasonably good 150w 8s charger there, and a good 350 watt meanwell to power it. They also have goodies you will need if you don't get them at HK. Wire, bullet connectors, a cellog 8 for checking cells etc. Your kit will come with a CA, so once you have sorted out any potential bad packs, you can monitor the whole pack voltage good enough with the CA, and have the cellog 8 in your pocket if you need to check an individual pack or cell's voltage at some point near the end of the ride home.

If you are riding every day, charging RC lipo will be a pita with a regular RC charger. But even if you get into bulk charging , you should have at least a funky 50 w RC charger in the house. Sooo handy for balancing a wonky pack when you need to do that. Doing bulk charging right is a bit pricy, you need some fairly expensive HVC LVC boards. If you go to bulk charging, you might want to go to 6s packs, so you need only 2 boards for 12s, rather than 4 for 16s.

If what you want is basic transportation that is legal in your state, ( 30 mph is likely to be illegal) you really should be building totally different. HS motor, 20 amps, 48v 15 ah pingbattery, 26" MTB and you are not going to look so much like the illegal homemade, unregistered motorcycle that the bmx build is. About 25 mph top speed, and blending in with regular bikes a lot more. 36v, to really be 20 mph legal, if that is the law where you live.

You gonna look like a clown when you spot a cop at 33 mph, and try to act like you are pedaling that bike.

 

[TRIGON391]

Alright so I did some more reading and took into consideration some of the input I you guys gave me. After thinking it through, a 25mph top speed seems a little more sensible and is something I can definitely deal with especially considering the legal aspects of it. I'm going to college in a small town so it won't be long before people catch wind of the kid on an obnoxiously illegal electrical bike flying around if I kept it at 30mph.

That being said, I've swapped out a few parts. First, instead of the crystalyte I picked the 9C motor because it's cheaper and still capable of making my bike do what I want it to do.

As for the battery, I bumped it down to 44.4v with the same packs. So 9 battery packs total, 3 in series and then 3 of those in parallel. That gives me 44.4v 15Ah which, according to the ebikes.ca simulator, will give me 17 miles at about 25mph. Another advantage of this setup is that it will be easy to mount 10Ah worth of the packs (six of them) on the bike for normal use, and I'll be able to toss the additional pack in a backpack for longer trips as needed. Still reading up on chargers and looking for the most cost effective way to handle that issue so I'll probably be back with more questions on that later.

So as of now:
-9C motor in 20 in rim 275.00
-36-72v 40A infineon controller 175.00
-might be a bit overkill but I like the upgrade potential it gives me if I ever want to rebuild/build a new ebike
-throttle 20.00
-CA 125.00
-shipping for all of that 91.34
-batteries 297.34 with shipping
And that all totals out to $983.68 still without the bike or charger so I'm slowly shaving the cost down. I know I could cheap out on a some of the stuff like the controller and make the setup a lot cheaper but I want this thing to be reliable and work for a while without me having to worry how long I have until something craps out on me in the middle of a 20 mile ride. I'm still reading into the batteries and chargers though, I feel like I might be able to come up with something a little more suitable or cheaper, if anyone has any suggestions please let me know and thanks again for all of the help so far.

 

[dogman dan]

I think you are really on the right track now. For an RC lipo noob, a 44v 12s pack is the easiest way to get going with the HK stuff. You should have nearly 30 still, but if you ride around 25 mph, you'll have a bit better chance of not pissing off the locals so much. Especially those always bike nazi campus chotas. But once off campus and on the back streets, hauling ass will not be such a problem.

At 12s, you can use a cheaper 48v controller,http://www.ebikes.ca/store/photos/C3635-NC.jpg It's not going to fry on you.

but the one you spec is a good choice too. With it, you can occasionaly go for an 18s 66v ride that's more fun.

Look at the 12s series paralell harness thread by Icecube 57 in the for sale new section. Makes 12s lipo charge up easy as pie with one relatively cheap 6s charger. Buy one from him, or solder your own. I have one, and it's sooo easy.

 

[TRIGON391]

Sorry to revive a thread that's a bit old but I've done some more research and planning and I think I have everything finalized for real this time (probably not).
Alright so after much deliberation I found that lipos are probably not the best fit for my project. They require more maintenance than lifepo4 batteries, and when factoring in the cost of the charger and connectors and a BMS, the lipo option is a bit more expensive than I initially thought. After researching, it's clear that ping batteries are a great deal and they seem to receive a lot of positive feedback on this site. I decided to go for the 48v 10Ah. I was calculating the total cost, and I read on the site something about customs. This battery will be shipped to the US, can anyone else who has ordered a ping battery to the US tell me what the ordering process is like? How much does it cost to get the battery through customs?

I also went with one of lyen's controllers, the 9 fet 4310 controller. Really glad I found out about his controllers, they are a great deal and ordering a controller from Lyen was a very pleasant experience he answered all my noobish questions promptly.

Motor is still the same 9C in a 20 inch wheel, and I was really leaning towards a mountain bike like the genesis, ultimately decided to stick with the BMX bike because it's a much more convenient size for my situation.

so:
110 for the controller and throttle
325 for the motor
450-500 for the battery, as long as customs and import taxes aren't too expensive
50 for a craigslist BMX
And I'll have a functioning ebike that does what I want it to do for around $985. I'm ordering these parts on a paycheck to paycheck basis, so the motor, controller, and throttle are on the way now. I will eventually purchase a cycle analyst, but I'm on a really tight budget so that kind of got pushed down on the list of priorities. I can't thank you guys enough for pointing me in the right direction for this stuff, like I said I'm gonna post my build here when it's all done so I can contribute a little to this community. Only remaining question is about ordering the battery to the US from pingbattery, the cost of customs and import taxes etc., so if anyone can share there experience ordering a pingbattery to the US, I'd really appreciate it.

 

[dogman dan]

Hmmm. Well, a 48v 10 ah ping can run that motor, but it will be pushed to the wall and beyond every time you start up from a stop or climb a steep hill. A ping is a 2c battery. That discharge rate means 20 amps is the max, and it better be at that max for a pretty short time.

I know money is tight, and you want the bike light, but the advised size ping for that controller is 15 ah. What is likely to happen is that the ping will wear out relatively fast. Relatively fast means it could still last a year or more, but not last 3-4 years like others have. The 10 ah size ping is ideal for lower wattage motor and controller sets like 350w. Your motor will pull 1200w leaving a stop sign.

One option you might look into is an A123 battery pack from Emissions Free, but it's a bit more pricy. Not thaaaat bad though, because you get a much better c rate, and hopefully the pack lasts you many years.

Something like this, http://www.emissions-free.com/catalog/i26.html

Or get the 15 ah ping at a similar price point, and have more range.

Getting the ping into the USA is no problem. You will lose tracking on the package while it clears customs, but it's not a deal where you get billed more. I have bought two pings and a few chargers, and never had a package hang up. Lots of other stuff from other china vendors too with no problems.

 

[TRIGON391]

Wow glad I asked before ordering. Looks like I'll be ordering the 48v 15Ah battery now, the range is more important than the speed to me, especially on the bmx frame. Haha looks like I'm off to sell some more old junk of mine on craigslist I'll post back here when my orders start coming in and I start building.

 

[stingray17]

The Ping battery at 10Ah probably does not have the discharge rate you want. The cells are rated 1C discharge. I have found that 1.5C is fine. If you are going to keep it at 15 Amps or so, no problem... although you don't really need a 9 FET controller, a 6 FET would be fine. But running at 20A for a few miles is a little bit too much for a 10Ah Ping. It certainly WILL work, I've done it before. But if used at 20A continuously it will shorten the life of the battery. I've done that before too. A larger, heavier 15Ah Ping battery will give you 22 Amps or maybe 25 without a problem.

You might be better off going for a LiPo setup - it might not be as complicated as you think. Or perhaps A123 pack from cell_man like this one or this one.

edit: right, what dogman said