fast e bike (2000+ W) with long range (100+ miles)?

[spectastic]

I originally wanted to build an electric motorcycle for commutes, errand runs, or just joy rides around the beautiful hill country around here. However, motorcycles are heavy, and consume around 116 Wh/mile on average, which is like a best case scenario of a zero motorcycle. On the other hand, electric bikes have much lower rolling resistance, narrower profile, potentially higher power/weight (mostly due to less weight) compared to motorcycles, which I assume is the reason why a commonly quoted figure is around 20 Wh/mile, for standard rear hub motor.

So the bike I have in mind can put out 2000-4000 watts that can get me to 35-50 mph, with a 2.5 kWh battery that can get me 100+ miles if I go gentle, and maybe 70 miles if I crank it up, which is totally fine.

I've browsed around a little bit, and saw that the vector bikes have exactly what I'm looking for, except they have a $6,500 price tag, which is actually a pretty good deal, but I'm a grad student.. Aside from the financial incentive of building my own setup, I would also like to sort of customize the bike to my own liking. However, I also realize that this may be a losers game. Sourcing the motor, BMS, controller, battery pack, custom rack to hold everything, all separately may very well end up costing more than a stock setup.

this is where I'm seeking guidance and advice from the knowledgeable people here. Can I build a 2000-4000W electric bike with a 2.5 kWh battery for ~$3000?

PS. I saw some youtube videos of a guy recycling a whole bunch of old laptop batteries spot welded together to make his battery pack, and got it done for pennies on the dollar. I realize that the battery is where most of the cost is going to come from, so as long as we can cut that down somehow, it should be manageable, right?

 

[amberwolf]

On the other hand, electric bikes have much lower rolling resistance, narrower profile, potentially higher power/weight (mostly due to less weight) compared to motorcycles, which I assume is the reason why a commonly quoted figure is around 20 Wh/mile, for standard rear hub motor.

That's for normal pedal speeds, not the speeds you're after.

35-50 mph,

At those speeds, you're back up to the motorcycle Wh/mile usage, because of wind resistance for the most part.

with a 2.5 kWh battery that can get me 100+ miles if I go gentle, and maybe 70 miles if I crank it up, which is totally fine.

Keep in mind a battery of that capacity is large and heavy. I have about a 2Kwh pack in SB Cruiser, about 35lbs IIRC. Some info and pics here
https://endless-sphere.com/forums/viewtopic.php?f=3&t=88416&p=1289761&hilit=pack+weigh%2A#p1289761

this is where I'm seeking guidance and advice from the knowledgeable people here. Can I build a 2000-4000W electric bike with a 2.5 kWh battery for ~$3000?

As you've realized, the battery is the big cost, and then the bicycle and upgrades to it to make it safe for the speeds you're after.

As for the power levels and cost--My SB Cruiser, whcih is around 3000-3500W peak, 2WD, didn't cost much to actually build, except for the battery and chargers (whcih I was lucky enough to have anonymous donors for), as everythign else was either recycled junk or it was cheap used stuff that needed repair. But it's only meant for 20MPH use (the law here in AZ) so it's brakes are not designed around stopping it from the speeds you'd be at (though it's a lot heavier so they would probably work from a lot faster on a lighter "regular" bike). I'd guess that I have actually spent around $400-$500 on it, other than tools/welding materials used to build the frame itself, and some of that was actually spent on previous projects and moved over to this one. Probably 1/4 of it was on tires/tubes before I switched to moped tires/tubes in back. Around 50-60Wh/mile is my power usage on the trike; it's decidedly un-aerodynamic. Also cuz it's heavy so stops and starts eat up a lot of power--on longer trips the wh/mile goes down.

Similarly, my CrazyBike2 is at least 4Kw, gets ~4seconds to 20MPH, and while heavy isn't nearly as much so as the trike (has half the size of battery, for instance). Again, not much into it moneywise, as most of it was used stuff bought cheap or repaired junk. IIRC its' around 22-30Wh/mile for the bike, even as un-aero as it is.


If I were to reconfigure the battery for more voltage (and less Ah) I'd probably be able to hit the speeds you're after, if it were allowed here, but the cost in power usage would be much higher than it presently is, from wind resistance. I'd also have to upgrade the brakes and possibly the tires to handle braking from those speeds.


If I had to buy the stuff for them new, however, I expect it'd cost at least three or four times that much, not counting the frame build itself, or the battery. The battery would probably cost at least as much as the rest of the trike (or bike), maybe more.

But there's cheaper options for batteries than what I used--some safer than others, some easier to assemble than others, etc.


As for making your own out of recycled cells, there's lots of threads about building 18650 packs out of recycled batteries, some of which will show you how to do it, and some to show you how *not* to do it. There's a lot of work to do to make a good one, lots of testing and sorting, before you ever get to building. The sticky index thread in the Battery Technology section has some good pointers to start with.

But for the most part, those cells are not meant for (or are old and can't handle) high power usage, so you either have to live with the problems this creates, or you have to build a much larger (and heavier) pack than you actually need, so that voltage sag and heat don't cause you grief.


The battery determines how well the rest of the bike will perform, so if you get a crappy battery, you get crappy performance.

 

[dogman dan]

My advice, as usual, is to back off just a tad on your goals,, or just go get a gas motorcycle. Not saying don't have the bike and get a gasser. saying get both.

But you definitely CAN have a 35- 40 mph e bike, fairly affordably. Here is mine,, does 35 mph easy, hits 40 mph on a downhill, but above 35 its lacking suspension, and a stiff enough frame to avoid speed wobble. For most bikes, that keep it below 40 mph idea pertains to speed wobble.

Fyi this bike was once a cheap steel cruiser with coaster brake. I welded on an attachment that lengthened it 12" greatly improving its higher speed handling. Go measure a motorcycle, it will be longer than nearly all bikes. For a good reason. So whether you go cruiser, or full suspension MTB, think 6" longer at least for 40 mph and above. While I had the welder out, I converted the bike to dual disk brakes. Nothing fancy, just BB7 mechanical disc.

The rear motor is a big one. Obsolete now, but similar motors are out there, crystalytes from Grin Technology, or Muxus motors and others straight from china.

The power you need is about like this. With the right voltage to make that particular motor spin that fast,, 1000w gets you 30 mph,, 1500w 35, 40 mph is 2000-2500w, and 50 mph takes a full 5000w or so.

Unless you are actually riding highway, you really don't need above 35 mph. So a 3000w max system is really all you need. The bike above is running 64v.. 18 lithium cells in series, that charges to 75v max, but I actually only charge to 73v. with my particular motor, 35 mph bike.

At 30 mph cruise, including some brief use of 35 mph I'm getting about 40 watt hours per mile. This is not bad. But if I feel like pedaling, about 20 mph is a comfy cadence for me, and then I get more like 25 wh/mile. Any faster, its just making me carry too much battery, and cost too much money, and even for this cargo bike, a 100 mile battery is a lot of weigh to pack around.

I carry 64v 15 amp hours. The way I charge, actually more like 12 ah. 12x 64= 768 watt hours. This is 30 mile range, still going a relatively fast 20 mph. 20 mile range at 30 mph. The main reason I don't carry more is most of my battery stash burned up in the garage fire. I was running 48v, and had 80 mile range at 20 mph. But carrying that much battery every ride is stupid. Carry what you need, and pack more only when you need that kind of range. Most days, 30 miles at full speed will be more than enough for your needs. When the fire happened, the battery I have now was outside in the battery stash. Should have had all of it there!!!

Which brings me to the last bit of advice, don't park a huge battery in your garage, attached to your house.

 

[spectastic]

thanks for the replies.

I do already have a motorcycle. it's not running right now though, and I just don't want to deal with ICE's. Maybe I'll just spend the time to get that thing fixed and call it good..

the thing about going 20 mph is that I'm a competitive cyclist too. I can go 20 mph for 60+ miles on my road bike, so the only way this is worthwhile to me is that if the ebike can perform significantly better than I can (eg. 30-40 mph averages), otherwise, it's just going to be sitting in the house.

would it be possible to have a spare battery laying around that can be hooked up to the main battery, on days where longer mileages are needed? I realize that in order for that to happen, the battery packs need to be balanced properly.. I figure if both packs are charged to the same voltage before being hooked up together, then that shouldn't be a problem, right? If they're the same pack, I can alternate them every once in a while to ensure their capacity fade is the same... But thinking about it some more now.. that won't be necessary..

I agree that carrying a large amount of battery is kind of redundant. But the advantage of doing that is you reduce the C-rate and DOD of the batteries, which is a good thing.

 

[ScooterMan101]

You can have 2 or even 3 or 4 smaller battery packs,

What you do is cycle them , one day use pack 1 , then the next day 2, and so on.

Then when you need to go longer distances, or higher speeds you use two.

You only need to charge more than one pack the same voltage when you put those two packs together to have the same voltage but more amperage/capacity .

Or an easier way is to just buy new batteries that have a high C Rate , like 4c and more.
That way you can just stop somewhere on your long ride, unplug one and plug in the other.

If getting Hobby Lipo's get ones with at least 25c rate, and get packs at least 5,000 mAh each.

There are cheaper ways these days to get new 18650 type battery packs, just look at the for sale new section for the do it your self connectors , then you can get just the batteries separately.

Do, Not , get recycled 18650's for higher amp hour draw bikes , like the one that you want to build. Just do it right the first time, better and lower cost , even after one year of use.

For this you will have to study the battery section on how to make and care for packs.

A easy way is to get Hobby Lipo's , BUT, they come with a very important Warning.

If getting Hobby Lipo's , Always , Charge outside, make your self a battery bunker that the batteries are always stored in when not in use on the bike. Charge them at least 3 feet away from anything flamable, preferable to do that with a charging bunker. You can make a battery bunker by going to your local Home Depot, or Lowe's and getting the big concrete building blocks , around $ 2 each, and plenty of concrete Paver Blocks 12 inch by 12 inch, and some pavers.

Build yourself a Bunker from those materials.

Some day I will post pictures of my battery bunker.

 

[999zip999]

To do the speeds and type of bike you want you want the number one best cells on the market not something that sits on a table that you just punch the keys on like recycle laptop batteries. You need the best A123 or LG or sony cells from a known guaranteed supplier. As an electric bike going 40 miles an hour you need the best cells you can get or a trailer full of those cheap cells to drag behind your bike. First ebike should be a 30mph model so you can understand how they work and you can figure things out from there. But your first ebike to be the wheelie monster 50mph 100 range is fiction.

 

[999zip999]

Start with a old comoly mtb get a cheap kit 250usd a 500usd 48v battery with bms and charger. Plug and play. 28- 30 mph. 30 miles ?

 

[amberwolf]

would it be possible to have a spare battery laying around that can be hooked up to the main battery, on days where longer mileages are needed? I realize that in order for that to happen, the battery packs need to be balanced properly.. I figure if both packs are charged to the same voltage before being hooked up together, then that shouldn't be a problem, right?

I have that setup, if you look at the linked post in my previous post--I have multiple large packs for long distances, and I also ahve smaller packs if I wanted to use them for just my regular commute.

I did actually start out using just the smaller battery, then swapping out for longer trips. But the last time I swapped out, I realized I might as well just leave one of the larger packs in, as the trike itself is so heavy already it doesnt' matter except for the space it takes up inside the cargo area.

I also did this with CrazyBike2--I had one smaller frame mounted battery, and could put a second in either of the cargo pods for more range.

But the advantage of doing that is you reduce the C-rate and DOD of the batteries, which is a good thing.

Exactly--which is part of why I left the big pack in SB Cruiser, cuz it's a power hog and is harder on smaller battery packs.


Probably not a concern for you, but just in case it hasnt' come up yet:

the thing about going 20 mph is that I'm a competitive cyclist too. I can go 20 mph for 60+ miles on my road bike, so the only way this is worthwhile to me is that if the ebike can perform significantly better than I can (eg. 30-40 mph averages), otherwise, it's just going to be sitting in the house.

You might also have to worry about law enforcement depending on the laws where you are and how much they care about them. You could conceal everything about a 50MPH ebike into what looks like a touring bike with big panniers front and back, but touring bikes arent' regularly seen going that fast. A bike that looks like a bike, being pedalled at up to 30MPH isnt' likely to draw that much attention especially if people already see you doing that sort of thing regularly. A bike that is going 50MPH, even with you pedalling furiously, is going to attract attention. It might not matter, if there's no one around to see it, or if thsoe that do don't care--if you did it here in AZ in various places, though, the first time you were seen would be the last time you got to ride it.

 

[Chalo]

the thing about going 20 mph is that I'm a competitive cyclist too. I can go 20 mph for 60+ miles on my road bike, so the only way this is worthwhile to me is that if the ebike can perform significantly better than I can (eg. 30-40 mph averages),

Set up a drive system to deliver close to 750W at 30mph, and then with your pedal input added, you'll be able to sustain at least 30mph. And it will still be a bicycle that feels and rides like a bicycle, unless you carry too much battery. Keep in mind that every added mph costs a lot more power than the previous one, so don't equip yourself to go faster than necessary to meet your requirement.

To make it effective at speeds below 20mph, use a mid drive like BBS02.

750W for 100 miles at 30mph, plus enough margin to cover efficiency losses, means you'll need close to 4kWh in the battery. That will be a horrible battery to carry, as well as super expensive. I'd plan to go less distance per charge, or else go slower to make the distance with less energy.

 

[spectastic]

this likely won't be a bike where I'll do much pedaling. at 30-40 mph, I'll be spinning 90-110 rpm on a 53/11 gear ratio, which isn't bad, but if I wanted a workout, I'd just ride my regular bike. also, at a higher rpm, it's harder to put power down, and I imagine I won't be putting in more than 150W average (my race bike has a power meter) riding that thing, and going 30+ mph, 150W is only worth a couple of mph, in my experience.

as for cops. I'm not too worried about them. they usually hang around the downtown/city area, where they pull people over for stupid shit. I've been pulled over on my bicycle... but away from the city, I don't see many of them. I can easily go under the radar in the city limits. I can/have also ran from cops before on my bicycle

I suppose what I'm really looking for is a small scooter or something. but the drawback is I don't want to register and pay taxes on it, and I want to be able to bring it inside buildings and stuff. so if I do decide to pursue this, I'm inclined to try to make this e-bike thing work.

as for the suggestion about learning to craw before learning to run, I actually used to be a mechanic in an e-bike shop, and would say that I'm more mechanically inclined than most. I'm now in grad school studying batteries. On top of that, I'm an avid cyclist who's ridden motorcycles. So in that sense, I think I have a better than average sense of what I'm getting myself into. Is there anything in particular I might be missing that warrants me to start from a basic build and work my way up? because I'd rather just go all in right now. they told me to start with a 250cc when I was looking for my first motorcycle, but 650cc worked just fine.

 

[zackclark70]

just buy a zero motorcycle if your after high power electric

 

[slacker]

Just curious if you were a mechanic in a e-bike shop and as of now studying batteries why are you asking questions on this forum as you seem more than qualified to research and come to your own conclusions? Just asking not meant to be offensive. Good luck in your quest. And i know that you will get a wide range of opinions here, this is a very good and well informed group. Ride on.

 

[Chalo]

One thing you may not be considering is that although a 650cc moto is just as good qualitatively as a 250cc moto, a 2kW 4kWh e-bike is not nearly as good as a 1kW 1kWh e-bike. It gets heavy, shaky, and awkward when you add so much weight.

One thing I failed to note earlier is that at 30mph and higher, you incur enough added drag by pedaling that it's often better to tuck and pull your knees in than to pedal. So if you don't gear the bike so you can contribute a lot of pedal power at such speed, you might as well not even bother.

If you're stuck on your initial performance benchmarks, you'd best do some weight budgeting and reckon how you'll package all the necessary components, and seriously evaluate whether it wouldn't be better to start with a light sport or dual sport motorcycle chassis instead. That way, your ride will be something you can straightforwardly register and insure, which is your legal obligation in any case.