E-bike project

[Faris_AtaAllah]

Hi everyone,

So I'm thinking about an E-bike project with high performance (150 kph)/range(200+ km) in mind. After a lot of research and reading different threads here (Thanks!), I think I'll go with Motenergy ME1507 and Sevcon Gen4 S6 controller combination. Battery bank with 96V will be used although for the long range target I need a beefy power reserve (maybe around 15 kwh), which leads to high weight.

I'd really appreciate your advice on this, especially the motor choice and its performance for such a high speed / heavy build. Any recommendations are welcome.

 

[amberwolf]

2kwh is probably going to weigh 30-40lbs including casing/etc depending on the cells you use (based on my ancient EIG EV cells). 15kwh will then likely be 200-300lbs. The volume is likely to be about that of a large suitcase, depending on the cells.

So I don't think you're going to fit it on an ebike (and an ebike-type frame, suspension, wheels, etc) probably won't handle the weight or speeds very well), but you might fit it on a large e-motorcycle, especially since you're looking at a middrive that will take up a large amount of space in your frame.

Have you done any calculations or simulations to determine the power you will need to reach the speed you are after, under the specific riding conditions you have? If not, I'd recommend it to be sure you get the right motor / controller / battery cells for your power needs, and be sure of having enough battery capacity to get you your range.

Which motor and type of drive (hub vs mid, and single-speed vs multispeed transmission) depends on your specific usage intent, and the conditions it must perform under (as well as your budget).

 

[Faris_AtaAllah]

2kwh is probably going to weigh 30-40lbs including casing/etc depending on the cells you use (based on my ancient EIG EV cells). 15kwh will then likely be 200-300lbs. The volume is likely to be about that of a large suitcase, depending on the cells.

So I don't think you're going to fit it on an ebike (and an ebike-type frame, suspension, wheels, etc) probably won't handle the weight or speeds very well), but you might fit it on a large e-motorcycle, especially since you're looking at a middrive that will take up a large amount of space in your frame.

Have you done any calculations or simulations to determine the power you will need to reach the speed you are after, under the specific riding conditions you have? If not, I'd recommend it to be sure you get the right motor / controller / battery cells for your power needs, and be sure of having enough battery capacity to get you your range.

Which motor and type of drive (hub vs mid, and single-speed vs multispeed transmission) depends on your specific usage intent, and the conditions it must perform under (as well as your budget).

Thank you for the reply.
Actually I meant using a large motorcycle frame for the reason you mentioned which is the large size of the battery bank.

I've done some rough calculations for the torque required to move the motorcycle and found a paper online with similar build specs (attached). I'm using that as a close enough reference for the project. They are using a 35kw motor, however, looking at their power consumption graph it only peaks there during hard acceleration. at constant speeds it's more 10 to 15 kw.

Planning to go single speed without gears if possible though I have more knowledge on the electrical rather than the mechanical side.

 

[amberwolf]

I've done some rough calculations for the torque required to move the motorcycle and found a paper online with similar build specs (attached). I'm using that as a close enough reference for the project. They are using a 35kw motor, however, looking at their power consumption graph it only peaks there during hard acceleration. at constant speeds it's more 10 to 15 kw.

Are they riding under the same road, terrain, and wind conditions you are? If your conditions are different, so will be your power needs. As an example, if they are on flat good roads with no wind and no hills, but you have bumpy gravelly/sandy roads with headwinds and hills or even just gradual slopes, it will take more power to ride your conditions. If they had more adverse conditions than you will, then it will take less power for you.

If your bike is aerodynamic enough (see the various Vetter designs like the Windjammer, for instance) it can take much less power at higher speeds.


BTW, if it takes 15kw to maintain the 150kmh speed you want to go for 200km, you will only get 3/4 of the way there, at best, with a 15kwh pack, because it can only do 15kw for one hour before it is empty, but 150kmh will only go 150km in one hour.

In that vein, I recommend making sure that you have enough extra pack capacity to account for degradation over time, and to take you around any unexpected detours to your destination, and overcoming any adverse conditions (such as headwinds). At least 25% extra capacity is a good idea, and 50% extra doesn't hurt, except that it may make the pack unacceptably large and heavy (and expensive). The extra capacity also means that there is less load on every cell (assuming you get the capacity by adding more of the same cells in parallel), which can make the pack last a longer lifetime.

 

[Faris_AtaAllah]

Are they riding under the same road, terrain, and wind conditions you are? If your conditions are different, so will be your power needs. As an example, if they are on flat good roads with no wind and no hills, but you have bumpy gravelly/sandy roads with headwinds and hills or even just gradual slopes, it will take more power to ride your conditions. If they had more adverse conditions than you will, then it will take less power for you.

If your bike is aerodynamic enough (see the various Vetter designs like the Windjammer, for instance) it can take much less power at higher speeds.


BTW, if it takes 15kw to maintain the 150kmh speed you want to go for 200km, you will only get 3/4 of the way there, at best, with a 15kwh pack, because it can only do 15kw for one hour before it is empty, but 150kmh will only go 150km in one hour.

In that vein, I recommend making sure that you have enough extra pack capacity to account for degradation over time, and to take you around any unexpected detours to your destination, and overcoming any adverse conditions (such as headwinds). At least 25% extra capacity is a good idea, and 50% extra doesn't hurt, except that it may make the pack unacceptably large and heavy (and expensive). The extra capacity also means that there is less load on every cell (assuming you get the capacity by adding more of the same cells in parallel), which can make the pack last a longer lifetime.

thank you for the informative reply, I'll surly take it into consideration.

I have one other thing that's I'm confused about. Should I go with the Sevcon or use a Kelly motor controller?
I've read a lot about both and people are divided in opinions when it comes to their ease of use and capabilities.

 

[amberwolf]

You'll have to program either one, but the Sevcon will require a lot more tuning, probably with the whole bike on a dyno, to get it performing well. It is a very complex controller with a lot of options, and for many it is difficult to even get it to the point the motor will spin, much less do what they want. Sevcon is not DIY friendly, and do not have any form of customer support unless you are a large OEM building many of the same vehicle. (or are rich and can convince them to take your money). There *are* people out there that do consulting that program Sevcons, if you can afford them and find them.

Kelly is simpler, but with less options, and can still be problematic to get going because of their very poor technical translations and terminology choices, as well as a number of bad choices in software design that make it very unclear what is going on. Some of their controllers' manuals state that the controller can actually be bricked by doing something as normal as spinning the motor while the controller is connected to the computer setup software, so you need to read all manuals and warnings carefully. But they do have customer support people, like Fany, that can help with some things, if you can get your problem across and you haven't done anything that voids the warranty.

There are plenty of other controller options out there, if you aren't set on one of those two, which you can look up and explore. There are quite a few threads here on the forum about them, from Fardriver to Votol to Sabvoton to 3Shul to Mobipus to ASI to DIY controllers like the Lebowki brain chip or VESC-variants, or the MESC, etc. Each has it's own advantages and disadvantages and feature sets.