Opinions requested by ambitious greenhorn

Hello everyone,

I am looking for advice for a build. I've wanted to build a powerful electric bike for years and I am finally getting around to it.I've researched for a few days now and I thought I would reach out with some questions I'm stuck on.

I basically want a low profile bike with as much power as possible. It doesn't need to go very far.

I would love recommendations for a motor, controller, and battery.

Here are my goals:
High torque, hard acceleration
top speed 40mph (I will normally cruise at 30) I will be riding on pavement
diy 18650 battery
8 mile range
mountain bike style, custom frame with a full suspension (not a dirt bike or a motorcycle!)
lowest profile possible
quiet
$2000 budget

I weigh 180lbs

Note: I have access to any equipment necessary to build this bike at my University.

What I think I know (please tell me if I'm wrong):

I will want close around 3kw to achieve my goals.
Hardware for systems more powerful than this are aimed at builds that are bigger, more powerful, and more expensive than I want.
The QS 205 v2 motor seems like a good choice considering that the v3 is very popular with you guys. However, it looks like everyone is running the v3 at much higher power than what I will be able to do.
Kelly controllers are also very popular and well liked.

Questions I have:

Does it make sense for me to run a QS 205 v2 or v3? It seems like this one is too big but other options are too small.
Are there good planetary hub motors for my purposes?
Should I go for a mid drive? The gear reduction would be nice, but I would rather not introduce this complexity to the drivetrain if I can get a satisfying amount of torque from a hub motor.
Will I have serious thermal management problems in the battery if I'm using a low capacity pack at the load I'll need?
Would it be insane to liquid cool the pack?
How do I choose a controller? There are so many options and opinions.
Will women be more interested in me when they see me with my amazing bike?

Thank you in advance! This community is awesome and all of your work is super inspiring to me.

Look at the leafbike build in my sig. It might be up your alley.

It uses a 35mm wide motor and can absolutely do 40mph all day. The motor is also easily 10lbs lighter than the QS, and probably a tad more efficient.

Mid drives are also popular, but beyond 1kw, most people have issues with drivetrain breakage ( bike chain is only really designed around 500w input.. )

Battery wise, if you want it to stay cool, you'll want to use 1/4th the maximum rated C of the cells.
There will be no need for liquid cooling if you do that. From fully charged to dead, you'll only see the cells go up a few degrees in temperature. seriously.

If you care about offroad performance than the hub is a non-starter.

Neanderthul said:

Will women be more interested in me when they see me with my amazing bike?

Click to expand...

I haven't had that experience, but i'm maybe a 6 in the looks department.
The only time i've got a thumbs up from a female was when i was seen riding my cannondale semi recumbent, which is the dorkiest thing i've ever sat on.

quiet

Click to expand...

I can vouch for the leafmotor being very quiet when paired with a simulated sine wave or FOC controller. This may go against what the ladies might be looking for though... When I was running the same motor with a trapezoidal controller, the sound it made on full acceleration was awesome. Good luck

A direct drive hub motor can generally handle much more than the rated power for short durations. My A2B motor is officially rated for 500W but I run it up to 2500W. For pavement use, a hub motor is hard to beat. For really steep off road trails, they overheat quickly.



The battery is often the limiting factor in a system. You don't need much range, but to get high current, you need cells that can handle it. Getting 20-30A out of a 18650 can be done, but pretty rough on the cells and only a few types can do it. Water cooling is an insane idea unless the water can be completely isolated from the electrical parts. What you really want are cells that don't get so hot you need to worry about it. Most folks just build the pack big enough so each cell isn't working so hard. Lipo cells may be a better choice for something like this.

Neanderthul said:

Are there good planetary hub motors for my purposes?

Click to expand...

If you mean geared hubs? Not if you need 3kw; though you could use 2WD, big geared hubs front and rear (like the MAC), and perhaps get peaks of 3kW out of that, but geared hubs are harder to get the heat out of, so if you don't get where you're going before you overheat them, you could have problems.

Check out http://ebikes.ca/simulator to try out different systems to see what it would take to do what you want with hubmotors, both as 1WD and 2WD, different motors, controllers, batteries, voltages, etc.

satisfying amount of torque from a hub motor.

Click to expand...

What does "satisfying" mean to *you*? It's different for everyone.

Do you want it to slam your head on the ground in a wheelie whenever you touch the throttle?

Do you want only gentle acceleration from a stop to max speed, taking a minute or two?

Do you want 0-40mph times of a couple of seconds?

Etc.

Will I have serious thermal management problems in the battery if I'm using a low capacity pack at the load I'll need?

Click to expand...

Depends on the cells and pack design.

Would it be insane to liquid cool the pack?

Click to expand...

Not exactly, but the weight and space and cost of the liquid cooling would almost certainly be more than simply having a large enough pack in the first place. If it fails, leaks, or causes corrosion or other cell damage, then the pack may become useless or have to be repaired or replaced, depending on what happens.

Air cooling is a whole other thing, though, that might not be impractical depending on cell type and pack construction methods.

I'd still vote for just using a pack that can handle it.

Will women be more interested in me when they see me with my amazing bike?

Click to expand...

That depends on them and their interests.

I assume by "low-profile" you mean "stealth", which means your bike wouldn't really look like more than a bicycle. (harder to do with the higher power systems, especially at such high speeds). So if they aren't interested in bicycles, they aren't going to turn their heads for you on it.

If you want those that are interested in some other appearance to be interested in you, you'd have to change the bike's appearance to match what they would like (even if you hate it's looks). If theyre just interested in fast bikes, they probably won't think much of somethign that "only" goes 40MPH, especially if it only does it for a few miles--they'd probably be more interested in motorcycles that go 3 digits+. If they're just interested in EVs, it probably doesn't matter what the bike does, they may be interested.

You have to decide who *you* are interested in, and target the bike to *them*, which may mean that you have to build a bike that you don't like, and that doesnt' do what you want it to do, or costs a lot more than you're willing or able to spend in either time or money or both.


I get some laughs and lots of wierd looks on SB Cruiser from people on the streets while I"m riding...but there are quite a few that are interested in it, when they stop and ask about it and we talk for a while--especially when we talk about it's uses for carrying rescued St Bernards around, for those interested in animal rescue or dogs, or it's uses for cargo, etc., for those interested in that, or simply the skills used to design and build it, for thos interested in that.

So...it depends on what (who) you're after.





Alternate power source :

I would go with leaf kit but with alum casted wheel (rim+hub) for casual riding.
https://www.leafbike.com/products/e-bike-hub-motor/brushless-motor-parts/18-inch-casted-hub-with-magnet-976.html

then buy the 1500W motor by itself
https://www.leafbike.com/products/e-bike-hub-motor/gearless-20-24-26-700c-28-29-inch/48v-1500w-rear-spoke-hub-motor-electric-bike-motor-spline-cassette-1110.html

but if you wanted the kit, with the lcd display then buy that,as you need the special controller for that display
https://www.leafbike.com/products/diy-bike-conversion-kit/24-inch-electric-hub-motor-kit/newest-24-inch-48v-1500w-rear-hub-motor-bike-conversion-kit-988.html

Some with say nay to the casted wheel, but I say yes!
Problem is if you dent the casted wheel, not much can do to fix it except bend it back, maybe MAYBE weld it maybe or maybe MAYBE brazing, maybe.

neptronix said:

Look at the leafbike build in my sig. It might be up your alley.

It uses a 35mm wide motor and can absolutely do 40mph all day. The motor is also easily 10lbs lighter than the QS, and probably a tad more efficient.

Click to expand...

Just subscribed to your youtube! Thank you. Yes, your leafbike is very close to the form and performance I am after. I like this controller in the 48v 120A configuration, what do you think? I saw that you're a fan of the 18 FET
https://kellyev.com/shop/kls-s/

Does this look like a good choice of a leaf motor if I decide to go with it?
https://www.leafbike.com/products/e-bike-hub-motor/gearless-20-24-26-700c-28-29-inch/48v-1500w-rear-spoke-hub-motor-electric-bike-motor-998.html

I am thinking that I'll build a 12S4P pack with legit Samsung 18650 25r cells. This would give me 48v and 10Ah. Based on what I know about batteries, I think it looks like I could safely run it continuously at 80A?

Thank you for the help!

markz said:

I would go with leaf kit but with alum casted wheel (rim+hub) for casual riding.
https://www.leafbike.com/products/e-bike-hub-motor/brushless-motor-parts/18-inch-casted-hub-with-magnet-976.html

Click to expand...

I have a pretty good idea of how I want this bike to look, and I'm not so sure how I feel about the casted wheel. I was going to look into lacing the spokes into the hub with a wheel that I find somewhere else. What do you think about that? Why do you favor the casted wheel?

markz said:

then buy the 1500W motor by itself
https://www.leafbike.com/products/e-bike-hub-motor/gearless-20-24-26-700c-28-29-inch/48v-1500w-rear-spoke-hub-motor-electric-bike-motor-spline-cassette-1110.html

Click to expand...

When you posted this I was in another tab looking at the exact same motor! I really like it.

amberwolf said:

What does "satisfying" mean to *you*? It's different for everyone.

Click to expand...

I want it to scare me, but I want to try to keep this bike lightweight. I want to have a hard time keeping the front wheel on the ground at launch, how about that?

the weight and space and cost of the liquid cooling would almost certainly be more than simply having a large enough pack in the first place.

Click to expand...

good point. I did some lab tests with my racing team while working on cooling strategies for 18650 cells by embedding them in a substance we call PCM (Phase change material). It melts at 60C and acts as a thermal buffer at this temperature due to the latent heat of fusion. Here is a picture of the test fixture I designed for a small scale test of 20 cells. I don't have images of the graphs, but we were able to push the cells way harder with the PCM surrounding them.

That depends on them and their interests.

Click to expand...

noted. I'm going to stick with my fedora and blue ray collection

I assume by "low-profile" you mean "stealth", which means your bike wouldn't really look like more than a bicycle. (harder to do with the higher power systems, especially at such high speeds).

Click to expand...

I'd like to have this thing look more or less like an ordinary mountain bike with like half of the frame triangle open. Many of the high powered bike builds I have seen are massive machines, which is awesome, but not what I'm trying to do right now. I just want to be able to park it in the tight spots where I commute to and I don't want to stand out too much. I have to see if my power demands can be met with the small form factor I want.

You have to decide who *you* are interested in, and target the bike to *them*, which may mean that you have to build a bike that you don't like, and that doesnt' do what you want it to do, or costs a lot more than you're willing or able to spend in either time or money or both.

Click to expand...

This is poetic.

I get some laughs and lots of wierd looks on SB Cruiser from people on the streets while I"m riding...but there are quite a few that are interested in it, when they stop and ask about it and we talk for a while--especially when we talk about it's uses for carrying rescued St Bernards around, for those interested in animal rescue or dogs, or it's uses for cargo, etc., for those interested in that, or simply the skills used to design and build it, for thos interested in that.

Click to expand...

I love it

Neanderthul said:

I want it to scare me, but I want to try to keep this bike lightweight. I want to have a hard time keeping the front wheel on the ground at launch, how about that?

Click to expand...

Liveforphysics' DeathBike used a frame mounted motor and a chaindrive to the rear wheel to do this... Look up "and you know this bike is dangerous" on the forum or youtube.
EDIT: This one: https://www.youtube.com/watch?v=xgptvv5FJWo

If you know what your weight and the bike's weight are now, then you can add in the approximate weight of the battery, and then use equations for leverage of those weights on the pivot point (rear axle) to determine the torque (ft-lbs or Nm) necessary to lift the front end. Then poke around the motors and controllers and batteries on http://ebikes.ca/simulator to see which systems are capable of that kind of torque at zero RPM up to whatever speed you'd like that to drop off at.

Doing it this way, you can find out what it would take, for certain, to do this.

FWIW, I'm still trying to determine this experimentally on the SB Cruiser trike, and 5KW in a pair of 20" wheels is not enough, even without me on it and all the weight it has behind the rear wheels.

CrazyBike2 had 2kW in a 20" rear wheel and it couldn't do it either. (about same wheelbase as SBC, but significantly lighter)


Another way to determine the torque is to directly measure with a sensor on the front end how much it takes to lift the front end off the ground with you on it (physically having someone lift the wheel against the weight). You can look up Justin_LE's testing posts on hubmotor torque measurements (I think it's in his simulator thread) for some methods of measuring this.

I did some lab tests with my racing team while working on cooling strategies for 18650 cells by embedding them in a substance we call PCM (Phase change material). It melts at 60C and acts as a thermal buffer at this temperature due to the latent heat of fusion. Here is a picture of the test fixture I designed for a small scale test of 20 cells. I don't have images of the graphs, but we were able to push the cells way harder with the PCM surrounding them.

Click to expand...

Allcell makes 18650 packs using a PCM, which allows them to use smaller packs for the same current output, and/or to have a longer lifespan for the cells at the normal current output.

I can't recall the thread, but there's some other testing here using PCMs for this as well. it doesn't add significant volume to the pack, but it does add some weight and cost.

Personally I wouldn't use 18650s for a small high current pack, simply because they heat up too much, even with good cells. I forget what cells they have, but I have a small 13s4p old-style "mini" pack from Luna, and it got hot just running SB Cruiser's old ("low power") configuration on my slow (20mph and slower) commute path, which is only about 2.5 miles each way (but with lots of stops and starts). A better set of cells could probably do that without getting hot, but it'd still get warm, and at a higher discharge rate (like you'd probably need) it probably would get hot, especially over a few miles of that kind of discharge.

There are a number of good threads about various 18650 cell brands and models; thunderheart has a few with test charts and such of his own, and there are quite a few older threads as well, by various people.

As long as you're willing to deal with the risks of RC LiPo, it's probably your best bet for a small high-power pack.

I'd like to have this thing look more or less like an ordinary mountain bike with like half of the frame triangle open. Many of the high powered bike builds I have seen are massive machines, which is awesome, but not what I'm trying to do right now. I just want to be able to park it in the tight spots where I commute to and I don't want to stand out too much. I have to see if my power demands can be met with the small form factor I want.

Click to expand...

The battery probably can be, with RC LiPo. You can even make a backpack battery that wont' change the bike at all, with a quickrelease connector that yanks out if you crash and fall off the bike, or whatever.

The motor...if you want a single hubmotor for 3kW continuous (dunno what power level you actually need) it'll need to be fairly large, which means heavy and rather obvious.

2WD means you can split the power between two smaller motors, which halves their heat load as well, though it also means you wouldnt' have wheelie power (cuz half of it would be in front, as well as the weight of that motor to help hold the front down).

If you only need high power for peak use, smaller motors can take that to varying degrees, as long as they get to cool off between peaks (again, see the simulator for graphs on power/overheating/etc).

THe one thing that has been a repeated problem with hubmotors, high power, and bicycles, is that the axle design sucks. It can have a problem with damaging dropouts, without proper torque arms/plates, and with those the axle itself can break. Axles can be replaced with better, differnet designs (there've been a few threads over the years; I have a design of my own I need to figure out how to build and test for SB Cruiser so I can fit fat enough phase wires to not melt them anymore, *and* not have the axles break anymore, yet still fit within the holes the covers have in them).

neptronix said:

Neanderthul said:

Will women be more interested in me when they see me with my amazing bike?

Click to expand...

I haven't had that experience, but i'm maybe a 6 in the looks department.
The only time i've got a thumbs up from a female was when i was seen riding my cannondale semi recumbent, which is the dorkiest thing i've ever sat on.

Click to expand...

Ha!
My experience is that a bike is making you attractive to women only when it has a pillion, commonly called a ‘bitch pad’ or politically correct: ‘passenger seat’.

neanderthul;
I used an infineon clone 18fet on that bike ( west coast electrics, em3ev, and some others sell it ), but that's kind of an older controller that's fallen out of favor.

I have no experience with kelly controllers.. but beware that their specifications are misleading if you don't understand them.
On the kls-s page you linked, you'll notice that when you select a 200A controller, you get a controller that pushes 80A continuous of motor aka phase current. The battery current ( which all other controllers are rated by ) figure is missing, and might be something like 50 amps or less.. my 18FET with '4110' FETs inside is rated at 60A battery current and an equivalent '20 second burst rate' for motor amps would probably be 300A..

The difference is that the infineon is sold as a 60A controller and the kelly is sold as a 300A controller. :lol:

Another thing about the kellys is that they have a completely different connector set than all other ebike controllers on the market.. if you get one, your first job will be rewiring everything from scratch. I like to just use the old infineon controllers because they have the same connectors that come on most hub motors... i also buy a matched throttle, ebrake lever, and 3 speed switch set so i don't have to mess with wiring because 90% of it matches up out of the box.

The motor you linked is the exact one i used. Except i would recommend buying the spoked wheel.

For batteries, go look at the datasheet of the cell you're interested in. Since you are new, i'll hold your hand for a sec and do the calcs for you on a 4p 25R setup. Let's google 'samsung 25r datasheet' and pick out a PDF.

http://dalincom.ru/datasheet/SAMSUNG INR18650-25R.pdf

Hmm.. the datasheet does not have a graph of the sag under load.. so let's hop over to the other best source of data.. lgyte-dk

https://lygte-info.dk/review/batteries2012/Samsung INR18650-25R 2500mAh (Green) UK.html



Okay, notice the 0.2A load here.. this is the baseline and the best performance you're going to get.
You want to do 4P and an 80A continuous load, so we can bust out calc.exe and figure out how much load we're putting on each cell like this..

4 x 2.4ah = 9.6AH
80A / 9.6ah = 8A load per cell.

Looking at the graph above, we have a 7A test, so that's close enough..

My opinion is that this is not so great.. there is a lot of voltage sag here and you only get 2.35ah out of the cell at this high of load.. at 8A you are looking at about 3.4v nominal.

If you loaded the cells at at 0.2A ( unrealistic, but we're just thinking of a baseline ), then it'd be a 43.2v nominal pack..
At 8A per cell, you are only getting 40.8v nominal..

Run more cells in parallel and this will look a lot better. Besides, 12s4p of Samsung 25Rs is only 383 watt hours.. I was running 12S x 25AH which is about 1100 watt hours and it only gives a ~20 mile range at 40mph continuous. So at 40mph, your pack would probably only give you 7 miles of range.

I'd recommend going to 6P and beyond with the 25Rs, unless your bike is just for going to the grocery store and back

ps.. if you want to simulate range on most motors, you can use this tool: https://www.ebikes.ca/tools/simulator.html

I've been so many rims, so a casted wheel would be alright to try out for awhile, and could always go back to regular style wheel. Its a users issue, I know that. I think it would be cool to try a casted wheel. However I am going to be moving into the motorcycle rims after this go around with rims, Alex DM24 (x2) with Sapim spokes 13/14 butted from www.ebikes.ca I had to use washers on the motor hub (mxus 3kw) so I am going to be inspecting this wheel a lot more then I have been doing. Right now I just got a flat tire, due to the Schwalbe Smart Sam tire having a weak sidewall, delaminated side wall, which I have had happen 3 times now on the Smart Sam. I bought them because it had extra padding on the tread. TBH I did notice the side wall, I just hoped it would last until I got home. Off to Crappy Tire for a Kenda 26x1.95. The issue with the Smart Sam maybe that the Alex DM24 rim was too narrow for the 26x2.15 Smart Sam tire. Either way I looked at some DH tires, they have thick sidewalls, but come in flavors too wide for a narrow IGH frame, Norco City Glide. If I were to do things over again, because of my height/weight being 6'5" and 375lbs I would have purchased a specialty rim made for heavy weights. I did see a video on this, but I forget the name of the rim now. Trekking cross-country was the theme, with a heavy weight. Cant find it but here is a link, https://www.livestrong.com/article/411045-what-are-good-bicycle-wheels-for-350-pound-riders/

Neanderthul said:

Why do you favor the casted wheel?

Click to expand...

https://www.peterwhitecycles.com/tandemparts.php
Cliffhanger in Black only, both 32 and 36 hole. This is a very stiff rim, so you only need 36 spokes for tandems or extremely heavy touring loads. 32 spokes is usually more than enough.

You already got a lot of great comments from the big dogs on this forum, all giving great advice.

Like most new guys, your dreams don't quite match what your reality will be. Boy, do I ever do that every time, with everything I get into.

First of all, top of the line customized, low profile, 40 mph is not really going to happen on 2000 bucks. ( Because in the end, you spend more than a thou on battery) But if you lower your sights just a tad, you can get a lot of what you want on the cheap.

Amazingly, the cheaper 500w rated hub motors can do 30 mph with ease, and keep that up for quite some time. You can run em at 2000w no problem. You might start with a "48v-1000w kit" on whatever your bike of choice may be. This will come with a 48v 30 amps controller in most cases, meaning 1500w. No, it won't hit 40 mph, but I strongly suggest you try 30 mph before 40. But, I definitely suggest replacing that cheap ass kit controller. When you do, get one that is capable of 48v or 72v, and 40 amps.


Then you run it on your 48v battery, which you still spent a crapton of money on, because even 30 amps from 18650's needs a very big battery. Later on, if your bike is really up to it, ( likely not anyway) you can go to 72v later.


One option that works good, or at least did for me, is modifying a beach cruiser for the custom frame. I did that for my second best ever e bike, after many years of experiments. Adding disc brakes to the steel frame easy, and the longer bike makes up to 35 mph on the street pretty doable. Its has done 40, but not really so great. Not why you think though, it just starts to speed wobble by 40 mph. Most bikes with a heavy motor and battery do, above 30 mph. Shocks not that big a deal, but a full suspension long bike would be better, and cost a lot more....


This is my long cruiser. It DOES meet your desire for lower profile, but I garan dang tee you its not low profile at all when it cruises 30 mph.

Like Dogman said, lots of good advice already posted here, but when has that ever stopped me....



This is my bike. I started with a 15aH (supposedly) 14S 18650 pack that came with my kit from High Power Cycles. Over time I've slowly changed lots of things on this bike, but by far the biggest improvement was going to a 16aH 20S MultiStar battery. I charge to 83V and only pull 45A from it.

I can stand up while riding, lean forward a little bit and roost the back tire on gravel/dirt. Your battery will be the most important component you buy and the best return on investment if you choose correctly.

neptronix said:

Since you are new, i'll hold your hand for a sec and do the calcs for you on a 4p 25R setup.

Click to expand...

Thank you SO much for this help! I am amazed that you were kind enough to walk me through this stuff. I am busy researching parts right now and I'll be back soon with a much better idea of what I'm doing after I break down all of the advice you and the others have given me.

Wolfeman said:

This is my bike. I started with a 15aH (supposedly) 14S 18650 pack that came with my kit from High Power Cycles. Over time I've slowly changed lots of things on this bike, but by far the biggest improvement was going to a 16aH 20S MultiStar battery. I charge to 83V and only pull 45A from it.

Click to expand...

I love the form factor. Thanks for the tip

dogman dan said:

Like most new guys, your dreams don't quite match what your reality will be. Boy, do I ever do that every time, with everything I get into.

First of all, top of the line customized, low profile, 40 mph is not really going to happen on 2000 bucks. ( Because in the end, you spend more than a thou on battery) But if you lower your sights just a tad, you can get a lot of what you want on the cheap.

Click to expand...

Yeah you're definitely right, I've set the bar pretty high. I'm gonna keep researching and see what I can do. I'll probably sacrifice top speed in favor of more torque. I've got a lot to learn and I'm hoping I can have a full design drawn up in CAD by the middle of May.

markz said:

However I am going to be moving into the motorcycle rims after this go around with rims, Alex DM24 (x2) with Sapim spokes 13/14 butted from www.ebikes.ca I had to use washers on the motor hub (mxus 3kw)

Click to expand...

I'm also looking at moped/motorcycle wheels, as well as the mxus motor. I need to figure out how to choose between the leafbike 1500w and the mxus 3000w, as well as find a suitable controller.

amberwolf said:

Allcell makes 18650 packs using a PCM, which allows them to use smaller packs for the same current output, and/or to have a longer lifespan for the cells at the normal current output.

Click to expand...

Interesting, I will check that out.

The motor...if you want a single hubmotor for 3kW continuous (dunno what power level you actually need) it'll need to be fairly large, which means heavy and rather obvious.

Click to expand...

That reality is dawning on me. I'm going to be forced to go bigger

If you only need high power for peak use, smaller motors can take that to varying degrees, as long as they get to cool off between peaks (again, see the simulator for graphs on power/overheating/etc).
The one thing that has been a repeated problem with hubmotors, high power, and bicycles, is that the axle design sucks. It can have a problem with damaging dropouts, without proper torque arms/plates, and with those the axle itself can break.

Click to expand...

I'm going to be designing the frame from scratch and welding everything up. I'll make sure to run FEA to ensure the motor does not introduce too much torque where it is mounted

All of your other advice..... thank you I read all of it and made notes. I'll be back in couple weeks after I get through some exams. Hopefully I'll have narrowed down the hardware choices I am looking at.