electric electric bike with 30-40 mph AND range??

[spectastic]

I dabbled with idea of electric motorcycles for a little bit and decided that bicycles would be WAAAYYY easier and more practical. Why waste 3x the amount of energy going 60 mph when you can get 3x the amount of range going 30 mph, and not have to worry about a bunch of safety gear? So I have in my head the design for the bike I want to build, and I'd like to run this by people with practical knowledge for any advice/critiques.

This is the bike I want to convert.


the bike:
- It's a steel frame
- I'd like to take full advantage of the frame triangle for battery space
- I would also like to retain the road style geometry for better aerodynamics compared to a wide mountain bike geometry.
- I plan to upgrade the disc rotors from 180mm to 203 mm for more stopping power.
- I plan to run thicker (maybe 35-38 mm) tires, and get beefier wheels with 32 spokes
the motor:
- I'm thinking about a 1000w front hub motor that's capable of 500+w continuous.
- I can produce about 200-250W, so maintaining 30 mph shouldn't be an issue ime as a competitive cyclist
- I'm still undecided about the front vs rear hub. I think the front hub is a simpler design, where I can replace the wheel easily. It would also allow me to retain the 10 speed cassette in the back instead of the 7-8s freewheel that comes with most rear hub motors.
- front hub would also help slightly with weight distribution. otoh, I'm not sure how front hub motors would handle at 30-40 mph.
- regardless of whether I go with front/rear hub, I figure it's probably a good idea to get a suspension fork instead of the rigid steel fork that I have for it. and if I decide to go with front hub, then perhaps thru axle is even better. the question I have here is whether it's even needed for pavement, and whether it will significantly affect the efficiency of the bike.
the battery
- I'm thinking of a 48V battery pack. However, there are some questions there, of how to build/buy a cost effective battery pack that conforms to the shape of the frame's triangle
- should I go with 18650 pack? if so that'd involve spot welding, which i don't have. however, this might be the cheapest option
- I'm uncertain which chemistry to go with right now. LFP is the cheapest and likely carries the most longevity. however, they likely charge slower, and aren't as energy dense. NCM is the most energy dense, but are expensive and deteriorates faster
- leading to the previous point. how important is having a BMS for a 48V system? Can you mitigate overcharging and capacity fade issues by having a good BMS? I'm pretty clueless when it comes to that area
- I'm curious whether there are other options as well, like modules you can buy.
- Perhaps there'd even be the option to add on an extra pack for longer trips.
- I'd like for there to be the option to stop charging the battery when the cells are at 80%, in order to prolong their capacity.
- how much capacity do you reckon I can reasonably stuff in there? 2-3 kWh?
the other stuff:
- i'm totally clueless when it comes to controller, bms, display, etc. I just know they need to fit together somehow. still need to do some research in this area, but I'm open to suggestions as to what's popular
- I would like there to be 2-3 different pedal assist modes, where I can set something like: mode 1 = 250W, mode 2 = 500W, mode 3 = 700W. and the input for the pedal assist would be forward crank motion, so maybe a hull effect sensor with a magnet rotor or something like that?

sorry for the long essay. but based on what I wrote, any feedback/tips would help. This is just a thought exercise for now, and I probably won't get to it until at least a couple of months from now. Thanks!

 

[neptronix]

You absolutely don't want a front motor if you want to go that fast. Range will also be a problem. Lack of suspension at high speed will also be a huge problem. A bike like this won't save you much in the way of additional rolling watts versus a mountain bike. So get yourself a nice dual suspension mountainbike, and keep this one for when your ebike is down.

If you want very long range, the only good way to get it is a recumbent or semi recumbent. Today's battery technology is rather limiting. The faster you go, the less time you get on the fun machine because aerodynamics get in the way.

It sounds like you have a ton to learn, but you are coming in here with the right mentality. I'll let the others field the rest of the question.

 

[ZeroEm]

I would go play with the motor simulator here
https://www.ebikes.ca/tools/simulator.html
Don't think speed and range should be in the same post. :? With that said, it really depends what type of roads you will be driving.
Speed and hard tail bikes are not fun on bad roads. dual suspension mountain bikes most don't have room for batteries/range.
I can not peddle at 20 mph or faster and help the bike. My brother has a small geared hub in front loves it, he commutes at 20mph. He now has a second battery for range. I am putting a front motor on a bike will let you know how I like it. most of the pedal assist setups have many levels to fit your needs. I don't do it that way I have two controls one for power and other for speed. I can set my speed low and peddle enough to keep my watts at zero until I get tired but always keep my speed steady. Take your time and read what people here ride and what there goals are and maybe you can find a bike that close to what you imagine.

 

[amberwolf]

Sounds like you're almost back to where you were a couple years ago:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=89695

- I plan to run thicker (maybe 35-38 mm) tires, and get beefier wheels with 32 spokes

The fatter the tires, assuming they'll fit within the frame, the more "suspension" you get out of them.

But...at the speeds you're talking about, a sudden flat will be no fun at all (on the front you'll probably lose all control and wake up in the hospital), so you will want to do whatever you can to prevent those.

Personally, I don't think you'll like any non-FS bike for the speeds you're after, but that depends on your roads. If they're perfect, it might be fine. IF they're like Phoenix, where all road edges (where bikes usually have to stay) generally suck, even 20MPH on a non-suspended bike is going to shake you apart. Couldn't imagine twice that speed under those conditions--if my bones didnt' fall out, the bike would probably fall apart. :lol:

- I'm thinking about a 1000w front hub motor that's capable of 500+w continuous.

1000w would get you part of the speed you're after, and you can use it for regen braking if it's a DD hubmotor.

But if you really want 40mph you're probably going to need more than 1000w continous.

You might want ot check out http://ebikes.ca/simulator where you can pick different setups and compare them, and see what their limitations are. Be sure to read the whole page first, and then start using the simulator, so you'll know what you're seeing.

- I'm still undecided about the front vs rear hub.

There's a lot of threads and posts about front vs rear:

https://endless-sphere.com/forums/search.php?keywords=front+rear+motor&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=front+rear&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

- regardless of whether I go with front/rear hub, I figure it's probably a good idea to get a suspension fork instead of the rigid steel fork that I have for it. .

It's going to change the geometry of teh bike, which afects it's handling and steering. You'd have to try it out to see if it's acceptable or not.

how to build/buy a cost effective battery pack that conforms to the shape of the frame's triangle

EM3EV sells triangle packs premade. Probably other places, too, but Iv'e got an old A123 block pack of theirs that still works, several years later. I don't use it much becuase I have bigger packs for the main trike now, but it's still useful for my brother's smaller trike.

Building one... is a complex task, and the tools to do it right can cost as much as the battery, by the time you figure out all of what you need to do (and however much you end up backtracking from problems or failures).

- should I go with 18650 pack?

If you wanna do that, I'd read every 18650-related thread there is on the forum first, to learn all the stuff you *don't* want to do, and then decide which of the many proven ways of building it you want to go with.

how important is having a BMS for a 48V system? Can you mitigate overcharging and capacity fade issues by having a good BMS?

Depends on the BMS and your usage. A BMS with a proper HVC and control circuitry will prevent overcharge, and LVC for overdischarge. Some are programmable (look up the Bluetooth BMS thread(s)).

Capacity fade...that's going to happen anyway. The harder you use the pack (more current draw, more heat, lower voltage it's run to, higher voltae it's charged to) the faster it will age.

I run no BMS on my EIG NMC pouch cell packs on the SB Cruiser trike/etc., but I'm never (except once, not by choice) running them down anywhere near their LVC point, and I'm not using them anywhere near their max C-rate. They're also much higher quality cells (for EV purposes) than most of the 18650 stuff you'll find in packs out there. But theyr'e expensive and hard to get hold of (mine came used from someone else's ex-projects).

But there is a BMS on the only 18650 pack I have; without it it would probably quickly get out of balance and be damaged by overdischarge of some cells, overcharge of others, becuase it's not big enough to run much of a motor for very long.

There's also a BMS on the A123 pack I have from EM3EV; I havent' tried running it without the BMS so I don't know how much the BMS helps on this one. But it makes it easy for my brother; he doesn't have to do anything but plug in the charger; the BMS takes care of everything else, and keeps him from accidentally running it down too far.

- I'm curious whether there are other options as well, like modules you can buy.

Leaf cells, or other large-EV recycled cells. They dont' fit well in triangles though, so you'd probably have to make pannier-packs out of them.

- how much capacity do you reckon I can reasonably stuff in there? 2-3 kWh?

In the triangle? A few hundred wh, most likely. Depends on teh cells. If you use 18650s, remember that the more capacity, the lower the c-rate, and the higher the c-rate, the lower the capacity. Some are a middleground type.

- I would like there to be 2-3 different pedal assist modes, where I can set something like: mode 1 = 250W, mode 2 = 500W, mode 3 = 700W. and the input for the pedal assist would be forward crank motion, so maybe a hull effect sensor with a magnet rotor or something like that?

There's a bunch of systems; the two most configurable are
--using a KT (KunTeng Kun Teng) type controller and LCD, because there is open-source firmware replacements for them by Casainho et.al. if you look around the forum.
--using a basic "dumb" controller with no display or programmability, and the Cycle Analyst v3 (CAv3) plus either a torque-sensing BB unit or a cadence sensor, throttle, etc., and handlebar switches/etc.,

either one will likely do whatever you want it to, but...you have to learn how to set them up, and at least with the CA, many things are interdependent so you have to go thru a specific setup process (teklektik's UUG, etc) to ensure you get what you want out of it. They'll both require "tuning" most likely to get what you want.

But they'll eventually get you exactly what you're after, whereas with most generic setups you're just stuck with whatever the factory programmed into them.

 

[neptronix]

dual suspension mountain bikes most don't have room for batteries/range.

I tend to disagree. There's some lightweightish electric oriented MTBS out there, and some older frames, usually from the early 2000's, can have quite a bit of space. I've built a few such beasts myself, with 1kwhr and 1.5kwhr of battery respectively, although about 2kwhrs could have been packed in with more higher density cells, providing a 40 mile range at 40mph.

The trick was making the shock blockoff plate, with just a drill, angle grinder, and parts from the hardware store.

All these bikes were a total hoot!

I can not peddle at 20 mph or faster and help the bike.

Oh geez buddy, you need a bigger chainring.. sometimes up to 52t will fit on a MTB. I can pedal up to about 40mph on the green bike above.

 

[flat tire]

Your initial premise is a mistake. Electric motorcycles are vastly more practical than ebikes for 30+ MPH at any significant distance. Even a scooter is a better choice for that use case.

 

[larsb]

It all depends. Done 30mph on this type of bike and an overvolted q128 motor for ages.

Works well if you're an experienced rider. 30mph really isn't that fast (compared to normal road bicycle speeds).

I agree it's not the best ride for comfort at 30mph but if you're an experienced road cyclist it's not something you're not used to.

Most of the people here just don't ride bikes like that and don't have the fitness to make it work.

 

[flat tire]

Yeah cuz 30 mph is so fast and you have to be really experienced to sit on a bicycle seat and do literally no work on a flat road going 30.

What the hell lol. Many of us have bicycles that do more than double that speed.

Anyway you totally missed my point while massively failing to brag about your fitness. Motorcycles and scooters are more practical for trips of any significant distance because they're more comfortable and more durable. It's not really about the speed.

 

[larsb]

Don't be so negative, no need for it. I just have a different view than most here.

A ride like that used to work well for me and I like the look of that bike. It's a fast riders bike.

With a small motor and battery i'd guess it's a nice ride but to be meaningful i think the goal should be to pedal and use the motor for assist. Now most people here would say it's pointless to aim for 30mph and still use your legs. It's not if you can keep close to those speeds unassisted.

What i meant is if you can do racing on a road bicycle then the tucked position isn't hard to keep, or even discomforting like it is for an average rider. experienced rider = experienced road bicycle rider in this case. It was not clear.

I agree that full suspension and an upright position is generally better, that road tires wear out like crazy and that it gets tiring to change brake pads so often and that you get punctures etc. That's business as usual if you ride road bicycles a lot.

 

[spectastic]

^^ yea I'm a pretty experienced cyclist. I honestly don't think having a rigid frame, or even rigid fork will be super bothersome for me personally. I'm not at all stranger to 30+ on a road bike unassisted and 40+ on descents. not bragging, just different strokes different folks. I'll sacrifice comfort for speed any day.

30 mph sounds fine by me. it's pretty much regular commuting speed, and I think it's very doable with 500w assist. but I agree 40 mph is getting into the scooter/motorcycle realm, and if I were to choose between that and having longer range, I choose the range. additionally, in order to pedal worth a damn at 40 mph, I'd probably need a larger sprocket in the front, like a 55t or something. I guess I'll settle for 30-36 mph for now, or whatever speed that's just short of spinning out in a typical 53/11

thanks for the responses so far. very helpful!

btw I 'm still partial to front hub motors. I've ridden them before, but they were slow 250w bikes. I'm wondering what is typically the max power that you can reasonably use on the front hub motor on regular pavement without running into traction issues. another issue is the dropout, which is why I suggested maybe going with a thru axle design, which I'd like to think eliminates the problem of weakness in the fork.

 

[neptronix]

^^ yea I'm a pretty experienced cyclist. I honestly don't think having a rigid frame, or even rigid fork will be super bothersome for me personally. I'm not at all stranger to 30+ on a road bike unassisted and 40+ on descents. not bragging, just different strokes different folks. I'll sacrifice comfort for speed any day.

That was exactly my viewpoint when i joined this forum some 9 years ago and had only test ridden some slow electric bikes, as well as pedaled around an 'acoustic bike' for 12 years. I thought, why not build a fast efficient bike on a suspensionless narrow tire frame that's light..

I don't know about one factor. That when you add a motor, you relieve some of the tension you normally feel, and having traveled higher speeds, you get lazy about dodging potholes and such. You don't want to slow down for road hazards that your bike and butt bones are ill equipped to deal with at >10mph higher than the vehicle was designed for. The idea of suspension comes to mind very quickly.

30 mph sounds fine by me. it's pretty much regular commuting speed, and I think it's very doable with 500w assist.

If you poke around the ebikes.ca sim, you'll see that sustaining 30mph means for 1000w continuous with most motors. Most people no roadbikes average like 15-18mph in reality, unless you're a genetic outlier. Expect a majority of your power to come from the motor if you want to go that fast. A very fit human being's output in watts is lower than 200w continuous.

But I agree 40 mph is getting into the scooter/motorcycle realm, and if I were to choose between that and having longer range, I choose the range. additionally, in order to pedal worth a damn at 40 mph, I'd probably need a larger sprocket in the front, like a 55t or something. I guess I'll settle for 30-36 mph for now, or whatever speed that's just short of spinning out in a typical 53/11

A lot of people disagree with me on this, but i think a 40ph continuous ebike that can pull 40 miles of range at that speed is completely possible; i mean, i built one myself, and am building another. But fat tires, thick brakes, a strong frame, and proper suspension become the absolute minimum of what you need, for safety and comfort once you start hitting motorcycle-esque speeds. ( yes, suspension becomes critical for safety, not just comfort, at a point )

btw I 'm still partial to front hub motors. I've ridden them before, but they were slow 250w bikes. I'm wondering what is typically the max power that you can reasonably use on the front hub motor on regular pavement without running into traction issues. another issue is the dropout, which is why I suggested maybe going with a thru axle design, which I'd like to think eliminates the problem of weakness in the fork.

Consider the design of a bicycle before you do that. A majority of your traction is on the rear wheel, and a front fork was designed to only take ~33% or less of the weight and forces that occur on a bike. That is okay when we are talking about lower power levels. Once we start going past 500w, you progressively increase the chance of the front wheel slipping while turning under power along a sandy road.

Front motors also induce funky steering effects. The larger the motor, the worse the effect.
Front motors also have the worst possible failure mechanism, in the case of a failure of the axle or fork.
You can forget very strong regen on a front fork because there is a risk of being sent flying.
At the power levels you want to push, you're going to need a strong torque arm setup, which completely negates the ease of the tire change from putting the motor on the front. Because of your body's weight balance, you'll still have a majority of your flats in the rear.

A strong front motor is much like a rear wheel drive truck with a front engine. You apply power where you have the least traction. Turning on a wet or sandy road while applying power, given that you're looking to push about ~1500w, might lead to an unexpected suprise one day.

Let me tell you, it's a lot better to skid out your rear wheel than your front!

 

[flat tire]

Well you could do 30 mph with 500 watt assist but you would need a roadbike and full tuck or some other impractical aero situation. Also you would need to be talking output power not input unless you have a super high efficiency drive. Back when I spun pedals my powertap said 30 was somewhere in the 400s with full tuck. I could only do that for less than a minute but the most elite pros can keep that up for like an hour. Crazy.

 

[ZeroEm]

by neptronix » Jul 27 2019 1:53am

ZeroEm wrote: ↑
Jul 27 2019 1:04am
I can not peddle at 20 mph or faster and help the bike.

Oh geez buddy, you need a bigger chainring.. sometimes up to 52t will fit on a MTB. I can pedal up to about 40mph on the green bike above.

Yes, a bigger chainring to peddle at a faster speeds. My Chainring is 50T my cog is 11 so my Cadence is 57. Sad is it not but I have the Ebike grin.

Now if spectastic can put out 37.5 watts at 170 rpm for an hour then he can get by with 1.5kw battery if not better shoe horn a 3kw one in a MTB. What motors do 40 mph for 40 miles and don't over heat?

I have a 1.8kw and if I peddle at my 18.5 mph then by https://www.ebikes.ca/tools/simulat...C40&motor=Leaf 5T&frame=full&kv=6.33&throt=53 I get 229 miles but only expect 150 miles. "Range"
I am not riding a MTB.