Electric Chopper Project

Hi, I recently bought a rolling chassis of which I would like to DIY an electric motorcycle. My inspiration is the Sine Cycle motorcycle. I'd like to have decent "motorcycle acceleration" as well as freeway capability (not just i theory). Range is not this posts concern but I would like to get at least 50km.



I am currently quite clueless when it comes to which motor I should buy. But I think it should be the next purchase. I've been looking at the HPM10kW (which seems to be offered from anywhere between $680 to $2500 as a kit), ME1507, ME1003 (Good price, but brushed?), HPEVS AC20 (Looks good, but pricy), Agni 95R. But because I have a vertical bar just where to motor would go I have also looked at hub motors (only just under 200mm between rear fender and vertical bar). Particularly "QSMOTOR 12000W 17inch In-Wheel Hub Motor with 6.0×17 Rim" interests me. It requires a rear fork width of 230mm but my fork width is 255mm, but that shouldn't be a problem right (just put in a spacer and ask them for a longer axle)?

Right now I think the ideal motor would be a hub motor since I would not have to do any frame modification and entire Otto-motor space could be used for batteries, and the space under the seat could be used for the controller. Do anybody know the price, quality, spec-accuracy and life expectancy on QS Motors hub motors?

Talk me into a motor or out of a motor. Any good alternatives that I have missed?

EDIT: Changed subject

Also, are there any good EU sellers?

I think this bike can be a good candidate for any type of motor, inboard or hub.

If you want a relatively easy to buid machine, then go for a hub motor. You could have very decent acceleration, and highway speeds wouldn't be an issue. The only concern I would have with using a hub motor would be that you don't have any suspension on the rear. So the motor would be quite exposed and you'd risk to destroy it if you ride on very bumpy roads. But one way of avoiding that could be to use a thick tire, like the Metzeller ME888 which is known to be very strong.

If you wish to go for an inboard motor, I think you'll have to modify this central pillar to get a bit of clearance. It is probably easy to do though, I don't think you should be too afraid of that. Inboard motors setup can allow you to go for a more powerful setup in theory, but I think almost any one can be happy with a 14KW hub motor actually so it will really be a matter of whatever you prefer.

If you plan on using the QS hub, I'd suggest you to go for a 16 inches instead of 17 (not entirely sure you can on the 14KW though). You won't have any problem to find good tires for a chopper at this size, and you'll have a slightly better acceleration.

Fork width can be an issue, you should ask QS if they are ok to manufacture a longer axis. And also, make absolutely sure everything is ok before they send it to you.

About the prices, you can get an idea here: http://www.cnqsmotor.com/en/article_list_89_1.html
Clearly that won't be cheap.
Regarding quality, well it varies. I personnally never had any problem with their motors, except once for a broken bearing, which is something I consider normal wear. Another issue that can happen is one or several dead hall sensors, it's not a super easy job to replace them but its doable. One thing for sure is that you can't really rely on their QC, as for many chinese products. Some friends of mine had broken magnets, bent laminations, and a few other problems. The motor worked fine anyways but yeah, quality isn't amazing or consistent.
They are pretty reliable though once they passed the few first months. Some of us tortured them for years with 10 times their power ratings and they are still alive today, so more than 7 years and probably around 100 000km. Mine is already 5 years old, its a 2000W and I'm running a 12 000W controller on it: still works pretty strong. So I wouldn't worry much.

It looks like a very nice base. Plenty of space for a gigantic battery, that looks like a promizing build!

Thanks you for an awesome reply.

The only concern I would have with using a hub motor would be that you don't have any suspension on the rear. So the motor would be quite exposed and you'd risk to destroy it if you ride on very bumpy roads.

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Never thought of that. I thought it would be a good thing with a hardtail, to not have all that motor weight behind suspension. I do expect to ride this bike over cobblestone (at low speeds) when cruising in the city as well at about 70km/h on fairly twisty roads around smaller lakes and such. For easiness of build as well as available space for batteries the hub motor is what I would want to get to work. Those prices though

If you wish to go for an inboard motor, I think you'll have to modify this central pillar to get a bit of clearance.

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I really need to reach out to a frame expect and discuss frame modification. I see pros with both motor options and being able to experiment with gearing would be nice.

I found the hpm10kW with the VEC500 controller here for $680: https://www.alibaba.com/product-detail/BLDC-motor-10KW-48V-72V-96V_60570264767.html
But at all other places I've found it it is much more expensive. What gives? That is a price I am willing to pay to get experience and a feel for it. If I got one of these, what voltage should I choose on the motor? Since I have got no experience with this at all (expect for my homemade 250W electric bike :wink, I don't know what to expect. I do not want to go all in and end up being disappointed.

ecustom said:

Never thought of that. I thought it would be a good thing with a hardtail, to not have all that motor weight behind suspension. I do expect to ride this bike over cobblestone (at low speeds) when cruising in the city as well at about 70km/h on fairly twisty roads around smaller lakes and such. For easiness of build as well as available space for batteries the hub motor is what I would want to get to work.

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Yeah, don't worry too much about that, as long as you get a good tire it should be all right. Won't be super comfortable of course, but I suppose if comfort was your your priority, then you wouldn't have bought a chopper in the first place
If it was my build, I think I'd go for a hub motor as well, but it really is a matter of preference, both hub or inboard are equally good solutions, with their advantages and drawbacks.

ecustom said:

I found the hpm10kW with the VEC500 controller here for $680: https://www.alibaba.com/product-detail/BLDC-motor-10KW-48V-72V-96V_60570264767.html
But at all other places I've found it it is much more expensive. What gives? That is a price I am willing to pay to get experience and a feel for it. If I got one of these, what voltage should I choose on the motor? Since I have got no experience with this at all (expect for my homemade 250W electric bike :wink, I don't know what to expect. I do not want to go all in and end up being disappointed.

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That doesn't seem to be a very powerful setup to me. More or less around 20KW. But that's for sure an interesting price.
To give you an idea, that would give you the kind of perfs you'd expect from a mid range, relatively low power 400cc.
Don't get me wrong, it's not bad, probably better than my own motorcycle since it's higher voltage, but I thought you were aiming for more when I red your first post.

The 14KW hubmotor is a bit undermarketed, it is named "14KW" but it can take about 5-8 times this rating for a few seconds. That would easily compare to a good 750cc, maybe even better. It's probably the most powerful hub motor commercially available, so obviously its expensive.
But I can totally understand that price is an issue though, especially because the battery won't be cheap either.

If you want to keep the hub motor idea, you can go with a cheaper, less powerful motor. In my opinion a 8000W QS273 can already be quite impressive. They cost around 500 bucks. As for the controllers, there are a lot of different choices, APT, Mobipus or Sevcon being quite popular, but it will depend on your battery. A 8000W hub motor will be able to take a bit more than 40KW, which should give you good perfs, something like 5 secs on the 0-60mph.

About voltage, those motors can cope with pretty much anything, so no problem. Usually, most people stay below 120V because it gets harder to find affordable controllers above these voltage levels. Generally speaking, the higher the voltage the higher the top speed (for the same motor winding), and the lower the current so less losses, less heat and better durability. It's always good to go for a higher voltage if you can, but up to some point the controllers get very expensive. I'd recommend you to go for anything between 72 and 120V, there are a lot of good controllers choices in the 72-96V range. Once you're decided on a controller and a battery setup, just tell the manufacturer of the motor your target top speed and your battery voltage and they will wind it according to your needs.

On the link you provided, the controller is rated at 96V, so you'd need a 96V battery in this case. I don't know if this particular controller is any good since I never tried it myself. Choosing a good controller is quite difficult and is a whole subject by itself, there are a lot of parameters that can make for either a good or a bad investment. Be careful on chosing your controller, since it is what will give most of the ride quality and personality to your bike. Throttle response, regen settings, startup power, max speed, torque curve, etc, all those aspects depend largely on it.
As for controller power, I'd recommend you to aim for something around 300-400A battery draw and at least 600A/phase. This can be lower if you supply it with 96V or more, but I hope it gives you some kind of reference of what to search for.

Dui said:

If you want to keep the hub motor idea, you can go with a cheaper, less powerful motor. In my opinion a 8000W QS273 can already be quite impressive. They cost around 500 bucks. As for the controllers, there are a lot of different choices, APT, Mobipus or Sevcon being quite popular, but it will depend on your battery. A 8000W hub motor will be able to take a bit more than 40KW, which should give you good perfs, something like 5 secs on the 0-60mph.

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Being able to take out 40kW for a couple of seconds sounds awesome. I am just concerned that 8kW will not be enough to sustain 100km/h. If I calculate with a drag coefficient of 0.5 I get that roughly 8kW is needed to drive a motorcycle in 100km/h. But the listed drag coefficient for motorcycle + rider is around 1.8 which gives that 20kW is needed (which is obviously not true). But 8kW continuous seems just a tad underpowered.

This graph though that I got from Electro Mobile seems to be right on the money.


O man, decisions decisions. I'll shoot an email to QS and see what the verdict is.

you need about 5kW for 100kph on a motorcycle.

and dont discard hub motors that fast. dont forget that building the mid engine mount, chains, tensioner and all that crap also costs money and time. with a hub motor you cut out all that stuff and you just have to bolt 3 wires and 1 plug to the controller and you are done. hub motor is also more effcient as you dont have any drivetrain/chain losses as you dont have a drivetrain.
not having chain noise also is a BIG plus when the bike itself does not make any noise. you will start to get annoyed at other sounds that are normally drowned out by the exaust.

flippy said:

and dont discard hub motors that fast. dont forget that building the mid engine mount, chains, tensioner and all that crap also costs money and time.

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I am not at all discarding hub motors. They are my primary choice. I just sent QS motor an inquiry. Lets hope they have good news.

I might be able to sell the old petrol engine for change.

ecustom said:

Being able to take out 40kW for a couple of seconds sounds awesome. I am just concerned that 8kW will not be enough to sustain 100km/h. If I calculate with a drag coefficient of 0.5 I get that roughly 8kW is needed to drive a motorcycle in 100km/h.

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My motor is just a 3000W and it sustains 120km/h without any problem. It could even go faster if I just tweak up the flux weakening.
No need to worry about that, with a 8000W I think 160km/h can be achieved pretty easily, just make sure you select a controller who has flux weakening.

I have got partial reply from QS. They say that they can only offer rim size of 17" instead of 15" as I want. They also say they can custom make a longer axle, but that it will take over a month. No issue with that. They can also offer same motor size with 8kW, 10kW and 12kW. No prices given yet.

The cabling does not run through the axle on these motors. So my question is (they haven't answered) how the cabling would work with a spacer over the axle? I assume the motor rotates around the axle so I'm not sure what they mean with the wiring not going through the axle.

Time to measure how big of a wheel I can put on.

Alright, so order has been placed for a 10kW hub motor (with controller and contactor). I'm hoping to get it in about a month or so.

In the meantime I am trying to figure out what tire to get. QS Motor recommends (according to website) 180/70-17 to 220/70-17, and I am having trouble finding any tires with those specs. 180/60-17 is a lot easier. How would that affect the lifetime/wear on the motor if I chose such a tire?

Current tire is 180/70-15. What tire should I get to fit under the current fender/mud guard with 17 inch rims? (Less frame modification if that is possible, unless bad for the motor).

BTW, frame inner width is 255mm so I have space for a really big tire if I wanted to. Would that make things better?

Thanks

I got my hands on four 48V37Ah battery modules. Each modules is 13s1p and I plan to wire them up 26s2p which, according to documentation, it should give me the following specs: Continuous discharge current 246A, Maximum discharge current (10sec) 670A -> Continuous power 32.35kW and peak power (10sec) 63.8kW. Plenty enough. 7.1kWh pack capacity.

I will remove the proprietary electronics from each module (since I cannot use it anyway) and replace it with a 26s BMS. I would like some input on both what BMS's there are to choose from in a configuration like this and how to wire it up.

Each module has a thin little wire welded to each "voltage step up" in the pack, giving me 14 wires per pack. On a 26s BMS will it be enough to parallell connect each "voltage step up wire" to the BMS or does it require a bigger connection? I do not understand the flow of current during discharge.

How should I wire the modules themselves. Will it be enough to join the 0V and 96V joints?

There are also four temperature sensors per module. I hope to be able to make use of them.

Below is a picture of two module mocks where they might be in the frame.

the 300A bms mentioned in the bluetooth bms thread should work fine if you replace the mosfets with real ones from a know brand and recallibrate it to 600A.

flippy said:

the 300A bms mentioned in the bluetooth bms thread should work fine if you replace the mosfets with real ones from a know brand and recallibrate it to 600A.

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Would you be so kind and provide a link to the post/BMS you are referring to? I found a "Bluetooth BMS" thread and it seems to contain a lot of different BMS advice. Are you referring to the ANT BMS, because seems to only support 24S? (https://www.aliexpress.com/item/32826820690.html)

Also, can you advice on my wiring questions?

there is also a 32S version.
https://www.aliexpress.com/item/32826469363.html

and your wires are simple: use 2~3mm (or more if you can get it) pure copper plates for the cell interconnects (several 1mm plates stacked is better to prevent cracking) and at least thumb-sized for the connecton between the battery and the controller.
you only need a single thin wire (probably already present if you reuse the existing loom in the packs.) from each cell interconnect and connect that wire to the bms. a bms scematic will make it clear once you found a good one.
the current on those wires is well under 0.3A so you need very thin wires, most bms already supply about 2ft of wire for each interconnect.
if you have the space i would recommend getting 1 more pack and try and shove it in the frame. from the looks you can fit that if you slide the box foward.
not for more power but for more range. driving at 80+kph will eat up your watts faster then you think.

have you decided on the controller yet? can you deal with a higher voltage? that would be better if you could crank the pack up to 32S.

Thanks for the controller tip. Seems that it might fit. I am still open for more suggestions though.

I'm hoping 4 such modules will be enough. Next step up would be 6 modules and that would require much more space and also the modules are 12kg. I think 48kg is a good round number. 7.1kWh should give me around 100km range I hope (at smell my surroundings speed).

I have ordered the Kelly Controller KLS96501-8080H.

What do you mean with cell interconnect? The parallell connection? From the guy I got the batteries from I understood that nothing more than the thin wires to the BMS is required for the parallell cells connection. But as I said; I do not understand the flow of current during discharge (or charge for that matter).

32s would require modification to the modules that I would like to avoid initially. I think my focus will be making it work with 26s2p and then make modifications after I can assess the result. I do not want to run anything beyond specs before getting a feel for things.

Long time since last post. It took a long long time to get the motor, and now when I finally have it it is without the required axle modifications. When it was finally manufactured (after a two month long, "no, we're not going to build it") it was without the discussed modifications, and I just told them to send it anyway, since I didn't have it in me to start the discussion again. So now I have to figure out how to modify the axle to make it work. No metal working experience here so this will be interesting.



In the picture below you can see the distance between the frame and the "lip of the axle". Rear fork is 255mm wide while the motor axle fits a 230mm rear fork. I'm guessing I have to cut away the current dropouts and weld on new ones on the inside of the current ones. I do not dare to bend in the frame and wouldn't know how to do it anyway.


Part of me think that the easiest solution it to get another frame but I like the one I have.

Here is how I will build and mount the battery pack.

local steel supplier will have the right size box steel.
make the weld bead intermittent and allow it to cool after each weld, otherwise the frame will warp like a pretzel.

or get a local welding shop and ask them what it costs to slap rhe mod.

ecustom said:

Long time since last post. It took a long long time to get the motor, and now when I finally have it it is without the required axle modifications. When it was finally manufactured (after a two month long, "no, we're not going to build it") it was without the discussed modifications, and I just told them to send it anyway, since I didn't have it in me to start the discussion again. So now I have to figure out how to modify the axle to make it work. No metal working experience here so this will be interesting.

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depending on the difference in length / etc you need, you could make axle caps that slip over teh existing axle that then have axle extensions on the end of them.

they would look a lot like pedal extenders
https://www.google.com/search?q=bicycle+pedal+extenders&tbm=isch

but would only be threaded on the outer end.

the hole in it for the existing axle to go into can't be threaded, it must instead be a very tight fitting doulbe-d shape just like the existing axle. preferably tight enough to require tapping onto the axle, or even an interference fit requiring heating of one and cooling of the other to install / remove.

when machining it, i would recommend makign a torque plate part of that section of the axle extender, so it is stronger and more able to resist motor torque and support the frame's dropouts, and be easier to bolt to the frame itself, so that axle and nuts are not doing anything other than keping the axle in position in the dropouts, if even that.

ecustom said:

View attachment 259113

I got my hands on four 48V37Ah battery modules. Each modules is 13s1p and I plan to wire them up 26s2p which, according to documentation, it should give me the following specs: Continuous discharge current 246A, Maximum discharge current (10sec) 670A -> Continuous power 32.35kW and peak power (10sec) 63.8kW. Plenty enough. 7.1kWh pack capacity.

I will remove the proprietary electronics from each module (since I cannot use it anyway) and replace it with a 26s BMS. I would like some input on both what BMS's there are to choose from in a configuration like this and how to wire it up.

Each module has a thin little wire welded to each "voltage step up" in the pack, giving me 14 wires per pack. On a 26s BMS will it be enough to parallell connect each "voltage step up wire" to the BMS or does it require a bigger connection? I do not understand the flow of current during discharge.

How should I wire the modules themselves. Will it be enough to join the 0V and 96V joints?

There are also four temperature sensors per module. I hope to be able to make use of them.

Below is a picture of two module mocks where they might be in the frame.
View attachment 259114

Click to expand...

What make of module?
thanks