Questions about emotorcycle battery and motor

[PortalKeeper]

Hello I’m new here and want to build my first emotorcycle for myself by attempting to do this dude’s build:

That is part 3 of it and I don’t think he has finished it. I’ve also been talking with someone at qsmotor.com and asking about the windings on the teeth on this motor (stock version): 17inch 12KW Hub Motor for super Motorcycle, Bike and Scooter...

The dude from qsmotor said the stock version is 5T but it can be manufactured as 6T, which he said might be a better fit for my use-case of the motorcycle (I live in Colorado and want to use it on the mountains so I may need a bit more starting torque. I was reading some threads on here and found some great information about this topic from @minde28383.

I also think but don’t know for sure that this version of the motor expects a voltage of 96V instead of 72V. So my question is how many of the cells that he uses in the video would I need to put in series and how many in parallel to get a top speed of at least 110mph?

I know that this is beyond what qsmotor recommends (they say not to exceed 100mph) but I would only go this fast for short bursts of time (just for excitement) so if there is a way to get the motor to that speed safely (without frying it), I would like to.

Maybe this can be done by using some sort of ff cooling system (I don’t think the guy in the video will use any electrical cooling system for the motor or battery)

Also, the battery and motor combination should support a range of at least 100 miles, and 0-60mph in under 4 seconds (3.5s would be nicer though)

The motorcycle won’t be used off-road, and I will probably be going around 65mph (our highway speed here) mainly and sometimes I like to go about 85-90mph when the road is clear for some long stretches of open road. And yes I want to also get it street legalized.

For reference: in the video he is using a 74V nominal battery with 77Ah capacity, and he uses two 10S16P modules, in series with each other to accomplish this. Here are the cells he is using and that I also bought: Lithium 2170 21700 Battery Cell 5000mAh 14.4A INR2170 M50 LT - By The Case, EV West - Electric Vehicle Parts, Components, EVSE Charging Stations, Electric Car Conversion Kits

I’m not sure what controller he will be using but he should definitely be using the motor I listed above (I am pretty sure he is using the stock version since this version expects a voltage of around 72V hence the 74V battery pack that he made).

Another topic that I’m not too experienced with is picking the tires to go around the rim of this motor. I believe he is using these ones (which he used on a previous build) but am not too sure: 180/55-17 Metzler Karoo Street

Any advice about picking the tires would also be really appreciated.

Thanks again for any help on this topic.

 

[peadar]

What bike are uising,?

 

[PortalKeeper]

What bike are uising,?

No bike, I’m building it like him

 

[peadar]

No bike, I’m building it like him

how are you going to get the diy frame street legal need a vin?

 

[peadar]

if you can with your skills you should go mid drive ,custom swingarm with built in motor, like Zero

 

[PortalKeeper]

how are you going to get the diy frame street legal need a vin?

Using this guide: Get Your Frame Registered and Titled

 

[PortalKeeper]

if you can with your skills you should go mid drive ,custom swingarm with built in motor, like Zero

Why do you recommend mid drive? I like the simplicity of the hub design he chose.

 

[harrisonpatm]

I'll try to briefly answer what you came to the forum to ask about:

So my question is how many of the cells that he uses in the video would I need to put in series and how many in parallel to get a top speed of at least 110mph?

Lots of variables to consider, but if you want a top speed of over 100mph, you're looking at somewhere in the range of 120-150v battery pack. 100v minimum. Especially if you want a hub motor. Try the grin motor simulator to play with some of the variables.

Also, the battery and motor combination should support a range of at least 100 miles, and 0-60mph in under 4 seconds (3.5s would be nicer though)

You are suggesting that you yourself want a range of at least 100 miles? This is overly optimistic. But just for argument sake. My motorcycle gets 100wh/mile range, because I never go above 60mph, and usually keep it to 45mph. And you want to go faster. So assume 120wh/mile. Times 100 miles, means you'll want a battery pack with 12kwh. From my voltage estimate above, let's say you go with a 100v nominal battery (this would be 28 in series, fyi). Meaning you'll want 120ah. The cells you listed are 5ah cells.

So with all of those back-of-the-napkin quick estimations, your hypothetical battery for 100mph top speed and 100 mile range, with those 21700 cells, would need to be 28s24p. 672 cells total.

Hopefully that will get you started thinking about what you might need and/or want. My advice is that your speed and range requirements are a bit high, so I would try to compromise on that a bit.

FYI, James's first e-moto 4 years ago was my inspiration to build one. I love that guy. Looking forward to him finishing his upgrade, if he ever gets around to it instead of one budget CNC or laser engraver review after another.

 

[PortalKeeper]

I'll try to briefly answer what you came to the forum to ask about:

Lots of variables to consider, but if you want a top speed of over 100mph, you're looking at somewhere in the range of 120-150v battery pack. 100v minimum. Especially if you want a hub motor. Try the grin motor simulator to play with some of the variables.


You are suggesting that you yourself want a range of at least 100 miles? This is overly optimistic. But just for argument sake. My motorcycle gets 100wh/mile range, because I never go above 60mph, and usually keep it to 45mph. And you want to go faster. So assume 120wh/mile. Times 100 miles, means you'll want a battery pack with 12kwh. From my voltage estimate above, let's say you go with a 100v nominal battery (this would be 28 in series, fyi). Meaning you'll want 120ah. The cells you listed are 5ah cells.

So with all of those back-of-the-napkin quick estimations, your hypothetical battery for 100mph top speed and 100 mile range, with those 21700 cells, would need to be 28s24p. 672 cells total.

Hopefully that will get you started thinking about what you might need and/or want. My advice is that your speed and range requirements are a bit high, so I would try to compromise on that a bit.

FYI, James's first e-moto 4 years ago was my inspiration to build one. I love that guy. Looking forward to him finishing his upgrade, if he ever gets around to it instead of one budget CNC or laser engraver review after another.

Okay this is very helpful, thank you. I had another question about range, in the stats of his first e-moto, he gave a range up to 100km and that was with a 4.3 kWh battery pack. From what you are saying, this range estimate is way off. Is this true? 120Wh/mile seems a bit high to me, and from what I’ve read on here, efficiency of hub motors does not really change with speed, although some people have misinterpreted that simulator’s results and thought it does (from what I gathered).

 

[amberwolf]

Air resistance goes WAY up with speed, and that eats up power to overcome.

Motorcycles (without full fairings, like Vedder-style) have pretty bad aerodynamics, so power usage can be very high (as high as a car, or higher, under the same conditions).

The efficiency of a hubmotor isn't constant--it depends on the current pushed thru it and the speed it rotates at vs it's winding (kV) and design. You can see this fairly easily in the ebikes.ca simulator when using the motors in the list that are thermally modelled; the worse the efficiency the faster they overheat. Just setup various conditions and then vary the speed it's being used at under those conditions to see the efficiency change.

You can manually work out the math on various motors to see the same thing (I don't know what the math is, but that should be out there in a lot of places). There may be other simulators that can show all the same things the ebikes.ca one does, but I don't know them.

 

[harrisonpatm]

Okay this is very helpful, thank you. I had another question about range, in the stats of his first e-moto, he gave a range up to 100km and that was with a 4.3 kWh battery pack. From what you are saying, this range estimate is way off. Is this true? 120Wh/mile seems a bit high to me, and from what I’ve read on here, efficiency of hub motors does not really change with speed, although some people have misinterpreted that simulator’s results and thought it does (from what I gathered).

Since I've seen and followed this guy, I know the first bike you're talking about as well. From his video description:

Nominal battery capacity = 4.3 kWh
Range per charge = ~80km @ 80% DOD (up to 100 km @ 100% DOD)

Let's round that to 90km, because it's unlikely and impractical to run it down to 0% every single ride (for example, when you're below 50%, your top speed drops and you won't be able to accelerate as hard due to voltage sag). 90km = 55 miles. Meaning he's looking at about 80wh/mile. That's good, better than mine, his is certainly lighter and more aerodynamic, so that tracks. But even if you were to use that figure for your above stated expectations, you'd still need an 8+kwh battery, minimum, to reach 100 mile range.

And I like James, he has very down-to-earth videos and techniques, but just like how evehicle manufacturers will advertise their maximum possible range under optimal conditions to sell their product, I wouldn't put it past a YouTuber to tell you his maximum theoretical range that he got one time, estimated, to make his project look good. I'm guilty of that too. I said 50 mile range on a 5kwh battery, right? Well, it's technically true that I have absolutely done that, 3-5 times. But they were warm days, I was not accelerating hard, I don't think I broke 50mph... you see what I'm getting at? Just because I'm not lying to you doesn't mean my 50-mile range is expected on every charge. On regular use, I rarely let my battery drop below 40-50% before I'm topping it back off.

efficiency of hub motors does not really change with speed,

That may or may not be true, I have no idea where you're getting that from, but what I'm referring to is that energy draw increases with speed, exponentially not lineraly. Meaning, when I estimated that you'd get 120wh/mile with your 100mph top speed, I was estimating a figure based on what it seemed like your riding habits might be:

I will probably be going around 65mph (our highway speed here) mainly and sometimes I like to go about 85-90mph when the road is clear for some long stretches of open road.

Faster means it takes more energy to reach and sustain those speeds. If your riding habits require more energy to achieve, then that's coming from your battery. If you stay at 25mph at all times, you could see something like 50-60wh/mile. Thats why you read about all the ebikes, emotos, and electric cars having lower range when your speed is high. And that's why I suggested that if you compromise on one of your project goals - range or speed - the other goal will become more achievable.

Hopefully I'm not getting you down. My suggestion in your case is this: you seem to be leaning towards the QS hub motor. I'd next find a controller that you can afford with a voltage range of over 100v. Then select a battery voltage that you're comfortable working with. Then just fit as many cells into your frame as comfortably and safely as you are able to. That will be your range: the amount of battery that you can fit into the bike is the amount of battery you can get, you know?

For reference, my current project to replace my existing e-motor (24s LFP), is 28s Li-Ion for 102v nominal, and it'll be 9.5kwh battery. So using my current wh/mile, I can estimate on paper that my range might be in the area of 95 miles. Which would be awesome, but I shouldn't expect anything over 80 miles. And my current top speed of 65mph for a few minutes, might be upped to 90mph max. But I shouldn't reasonably expect cruising speeds of anything over 70-75mph.

 

[PortalKeeper]

Sorry I don’t know where I was getting that information from either lol, I may have just been blabbering about something I read but didn’t fully understand. But your input on this is incredibly helpful. I think you are right that I need to make compromises and look at this motorcycle more for fun than an all purpose vehicle. Thanks so much for that piece of wisdom.

I also like him and his builds. I think going forward, I am just going do the exact build that he is doing and closely repeat as many of his techniques that he shows in his videos. After checking batteryhookup, I learned that those used cells he is using in the new build (the m50lts) are out of stock so I don’t think I have a choice but to make the exact battery as him, unless I buy them new, or if it is possible to mix and match different types of cells (I doubt it).

This way too I can just follow what he does and leave the responsibility of decision making about things like how extra battery weight may affect suspension, or whether cooling will be required if I were to increase the number of cells in the battery modules compared to him. Although I will play around with that simulator to try and estimate what the range/top speed this build will amount to.

Thanks again

 

[Dui ni shuo de dui]

Motorcycles (without full fairings, like Vedder-style) have pretty bad aerodynamics, so power usage can be very high (as high as a car, or higher, under the same conditions).

It is true that motorcycle have very bad aerodynamic coefficients, much worse than any car, even SUVs and pickups are better. However the frontal surface area also matters in the drag force equation. Since motorcycles have a very low frontal area the total drag force of a bike is usually a lot lower than a car's. Hence power usage is actually lower.

Just a little precision, hope you don't mind and sorry for the off topic


Edit to contribute briefly to the topic:

The requirements are too high given today's DIY technology, at least to my knowledge. 110 mph is reachable, 100miles of range is doable and minus 4s on 0-60 is doable... but not three at once!
Pulling all of that in one build will be very difficult, very expensive, and require knowledge because none of these goals is easy to reach even separately.

I suggest you pick the one you care about the most amongst the three and then work your way from there to see how you can compromize on the others