Will this bike work for a 16KW build?
- Thread starter Haien
- Start date
E-HP said:
I have not, no. Yes, maybe 4kw would be enough to saturate my torque needs for now, 4 times more torque than my 1kw bike would be pretty quick, but I am sure I will crave more eventually, "power is addictive". Making 5 bikes with increasing power is in the end much more expensive and time consuming than making one too powerful from the start.
It is pretty funny that last year when I wanted to build a 2-3kw bike thinking that was quick enough, people were saying the qs 205 v3 would be the smallest motor you can call quick, and that I should build with that one if I wanted something with good pull, but now when I want to build with the 205 v3, people are saying 2-4kw will be quick enough. Maybe I am in the wrong part of the forum if I want to build a quick dangerous bike. Where is flat tire?
Back to your original question, some bikes have 148 dropouts but they're relatively new AFAIK. Many have fabricated beefier dropouts; just look for them. Probably don't plan on welding them to the frame unless you can heat treat it. Possibly you'll need to beef up the chain and or seat stays for the additional power, and definitely consider moped wheels and tires to provide added protection for the "quicker" trips.
Haien said:
Time for a math check. For 16kW @ 82V nominal (22S), you need ~200A continuous. Using high current 18650 cells, e.g. Samsung 25R, 2500Ah, you need 8P. 25Rs can provide 20A when new and under ideal conditions. 8P of 25Rs can provide 160A. For 200A, you'd need 10P (220 cells), or 22lbs of cells. So 22S10P, 25Ah, 200A, or 7.5 minutes of riding at 16kW.
If you go lipo, then using 6S 20Ah and 4S 20Ah in combination 3x6S, 1x4S for 22S, then that comes to 21.6 lbs, using Turnigy lipo packs. At 12C, that would provide 240A when new, and under ideal conditions. I would worry about crashing with 22lbs of lipos strapped to my back. Do you have experience with big lipos? They're economical, but dangerous, and I'd probably go for something like 25Ah+ worth for 20Ah of usable capacity, or 6 minutes of riding at 16kW, or 7.5 minutes if you run them down.
Since you're looking for 16kW peak, you don't need as big or heavy a motor for that, just a battery to support it. I've hit 7kW peak into my cheap 1000W ebay hub, but 4kW (peak) regularly. I'm guessing the Leafbike motor suggested earlier may take 12kW for very short bursts; there's probably experience members that could speak to that though.
I have some familiarity with high power motorcycles. I have one that will power wheelie in the first 3 gears just by rolling on the throttle (no revving or clutch). The ascending torque curve of a motorcycle engine is way easier to control than the descending torque curve of an electric motor. Rolling on the throttle on a high power electric bike, is like running your motorcycle up to 6000 rpm into the meat of the torque curve, and dumping the clutch. So you have a lot of unusable torque for the first 15 mph or so.
2old said:
Hm, I will have to keep looking for bikes for a while I guess. Yeah no, I won't be welding anything to an aluminium frame, the ideal bike would have removable dropouts I can just replace with my own homemade ones. I will go with moped/moto tires and rims, but beefing up the chain? The qs 205 is a hub motor, and will therefore put no additional stress on the chain.
Haien said:
4.5kg with is 900wh with high discharge 18650, good for about 7kw. Either samsung 40t or molicel p42a, 60 cells 21700.
Below 5kg it is a non issue, with low quality backpack it is annoying but not bad, high quality backpack (that sits on waist) it is fine.
Going above that you will feel like you are not biking but transporting something. I saw a guy had 8kg pack in backpack, he said it was bad and couldn't wait to get rid of it.
E-HP said:
My battery will be 22s of 3.65v nominal cells rated at 100A continous and 200A peak. When fully charged to 4.2v a cell the pack should be able to generate about 200A*80.3v=16060W (using nominal voltage to account for sag of the fully charged pack). Even if the leafbike motor could take 12kw, I still think the 205 v3 4t will be my best bet. Feeding small motors too much current seems to mostly make more heat from that power (ask dogman dan), and the 205 is a much bigger motor. 16kw is on the edge of what the 205 can handle, so I don't think going with a smaller motor is a good choice, even if it would fit smaller dropouts.
Yes I will have a lot of unusable torque, and that's what makes it thrilling. If I don't do what jackflorey said, to just floor the throttle, and I use a torque/current throttle with some throttle delay, I should be all good.
Also I weigh a lot, so the power may seem higher for some of you than it is to me, proportionally to my weight.
Chalo
100 TW
Haien said:Hm yeah it may not be an optimal solution, but is is at least pretty stealthy. If it becomes too bad I might have to find another solution. Bike basket?
Why do you have to be stealthy? Electric motos are allowed. Just buy or build one and don't try to deceive people about it. It's easier that way, and you can get the typewriter-sized chunk of battery off your back, literally.
Find a 50cc dual sport or supermotard bike with a knackered engine, and convert that. Overall it would be easier, cheaper, and more comfortable.
Chalo said:Haien said:Hm yeah it may not be an optimal solution, but is is at least pretty stealthy. If it becomes too bad I might have to find another solution. Bike basket?
Why do you have to be stealthy? Electric motos are allowed. Just buy or build one and don't try to deceive people about it. It's easier that way, and you can get the typewriter-sized chunk of battery off your back, literally.
Find a 50cc dual sport or supermotard bike with a knackered engine, and convert that. Overall it would be easier, cheaper, and more comfortable.
In my country, 250w pedal assisted up to 25kmh is the legal limit of an "ebike", over that, and it's legally a moped or motorcycle. That is why, and I can't fit the battery on a normal dh bike frame, that's actually the main reason.
That would actually be one of the worst options stealth-wise, as tuned mopeds regularly get stopped by police for test rides, but it would be better in ever other way, yes.
E-HP said:
No, a 16kw build. It will output a max of 16kw, therefore it is a 16kw build. Continually the bike can't use more than 4-6kw even at top speed, as long as you're not going up a steep hill, as it will be set up that way. What my battery can output continually is therefore irrelevant.
E-HP said:
I guess you could call it a 4-6kw or whatever it draws at full speed -bike, even though that would be wildly mislesding, but why would calling it a 16kw bike be silly? Whats the difference between my bike and a "true" 16kw bike? Both would output the same power, at least during acceleration (as long as you don't mean a "true" 16kw bike would have an even higher peak, as 16kw would be continually, then sure, but why define it that way?).
Edit: Lets say I doubled my battery pack size, going with 2p instead of 1p, technically making the pack able to output 200A continually, would that make my bike a "true" 16kw bike (actually we would get a bit higher power from 22s2p at 200A as the voltage sag would be less severe, but let's not take that into consideration)? Both the 1p and 2p bikes would be able to output 16kw during acceleration, 16kw peak, and would then use whatever it uses at top speed, probably between 4 and 6kw. Why would the 1p bike be less of a "true" 16kw bike than the 2p? If you want to call it a 4-6kw bike with 16kw peak, sure, but I think calling it an 8kw bike just because that's the continual limit of the battery pack would be silly. Do you see my point? Continous battery power is irrelevant.
Even if it would be able to use 8kw continually, if it was "geared" to go much faster that is (had higher kv, bigger rim, or higher voltage), the motor would overheat so fast that it would still not be able to do 8kw "continually". Rated continous battery current is irrelevant.
Haien said:
It's a system, and the rating of the system is based on the component with the lowest rating, which is what limits it's ability to run continuously at that level. That's how ratings work. My bike is a 1kW "build". The battery can provide 3kW continuously, the controller can provide 5kW continuously, the motor can handle 1000W continuously. With the Statorade, the motor may be able to handle 1200W continuously. It's not a 7kW "build" just because it can deliver and handle 7kW for a really short time.
The difference between 16kW and 8kW is that instead of being able to ride for 7.5 minutes, you get to ride for 15 minutes with a 20Ah battery, so a big difference, even though most people like riding longer and further than that, regardless of the thrill. On the other hand, with 20lbs on my back, maybe 15 minutes is enough.
My advice is to pull the trigger and build it, since you've collected most of the advice you need to make an informed decision. As the saying goes, Sh@# or get off the pot; it's been over a year already.
JackFlorey
100 kW
That's a lot less likely on an IC motorcycle. IC engines deliver low torque at low RPM, which is why you have to rev fairly high on an IC motorcycle for decent performance. Electric motors have their highest torque at low RPM. That's what can get you.Haien said:
Hey, you can do whatever you like; there are no rules here about what you can and can't do with advice. I think one of the best uses of this forum is to learn from other people's mistakes so you don't have to duplicate them. But if you want to do so, no worries.
E-HP said:
I see what you mean, and I would agree if my bike would be configured to top out at a speed using 8kw, the problem is just that my bike is "electrically geared" to top out at a speed only drawing somewhere between 4 and 6kw, so having a pack that could generate 16kw continously would make no difference. Both my and the "true" 16kw bike would make 16kw during acceleration, and then use up to 4-6kw cruising. Therefore, no, my battery won't drain in 15 minutes, there is no way to practically make that happen (unless you constantly accelerate and decelerate, or find a comically steep very big hill, which is not practically possible), as the 8kw number is irrelevant. Call it a 4-6kw bike with 16kw peaks if you want, but it's not an 8kw bike, the 8kw figure is totally irrelevant.
Yes, I will pull the trigger once I find the right bike. It hasn't been a year, it's been maybe 3 weeks, at most, planning this project.
JackFlorey said:
That really depends on the power of the ice motorcycle, with a motor big enough, it will dump you going full throttle anywhere on the rev-range, but yes it is true that ic engines are generally less likely to dump you, given the power of the ice and the electric bike is about the same.
Haien said:
Nothing in you build is frame dependent but the dropout width. You plan on carrying the battery in a backpack, and you can find a place on almost any bike to hang your controller, and your motor choice sounds like a done deal. Order the parts and you'll figure out the frame by the time they arrive. There's still a few good months of summer weather to ride. :thumb:
Hillhater
100 TW
Backpack battery is not a bad option.
It has many “pros” and a few “cons” , but still a practical solution.
Cable sizing and losses may be an issue fo 5++ kW power though ?
I ride with a 20+lb backpack battery, and after 5-10 mins i dont even notice it is there.
2+ hr ride is no problem .
It has many “pros” and a few “cons” , but still a practical solution.
Cable sizing and losses may be an issue fo 5++ kW power though ?
I ride with a 20+lb backpack battery, and after 5-10 mins i dont even notice it is there.
2+ hr ride is no problem .
