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Flatout
27 March 2018, 0432
Hey there folks,
just wanted to say hi. I'm a 28 years old engineer based in germany.

I'm planning on building a street legal electric moped and hope I can find some information here. I was planning on using a 4KW Hub Motor and I'm aiming for a range around 50km.
Before I start asking stupid questions can you recommend any good reads/tutorials/basics? As always with such a project, I'm starting with a blank page, not knowing where to source stuff or what mistakes to avoid.

Best regards :)

T Rush
28 March 2018, 0149
welcome aboard....I'm also pretty new to this(tho I did a bunch of research over 10 years ago when I first thought about a DIY EV, but now going to try it again) so maybe I can help to show you some things I recently found to bring you up to speed


- I found a really good place to start, is to learn the language
http://elmoto.net/showthread.php?t=3392
...thats the ElMoto dictionary...while its very long, and I'm sure you know most of those terms...it really helps to have them fresh in your head, so that when you come across them you know exactly what they mean related to an EV


- from there I found it really helpful to find a big name manufactured eMotorcycle that is about like the one you or I want to build, and just see what they did, and try to reverse engineer it to figure out why its like that....or of course find other DIY projects that you like, start looking at things they did that would work well for you, and stuff you would want to change...I think it really helps to know the bike final weight, max speed, max range, range at different speeds, battery kWh rating, motor kW rating, controller type, final drive ratio...to see what results they got and how they differ from another bike setup, compare that to what results I'm after, and which ones I'd want to improve or sacrifice


- it seems the main thing that makes up an EV is the battery...this really is about 80% of the bike...and this is the power; as unlike an ICE that 'makes power' all the other parts of an ebike(..twist throttle, controller, motor, drive ratio, tires..etc) only transfer that battery power into motion...but still the electric power is made somewhere else, the battery is just how much of it you can bring with you...also how fast it can charge and discharge is a big factor to how well it will work(C rate), along with how much it holds(watt hours)
...the battery is going to be the primary physical concern too; how much it will weigh, and how it can fit, esp in a smaller bike...as well as the range, speed, and acceleration; too small and you can't go far and fast, too big and you can't go quick and nimble
...do know the different battery types and what native voltage each one has per cell...then what you can find for how big each cell can be for the ah(amp hours) so that you can design your battery pack(if it can be all cells in series to get to your target voltage if each cell is rated high enough ah...or if you have to do series and parallel cells to also raise the ah...you will see this a lot, like: "20s8p" or something, thats 8 cells in a parallel group and then 20 of those cell groups in series for a total of 160 cell battery pack)...know the difference between a 'cell', 'module', and 'battery'
...have your pocket calculator(cell phone) always ready(I'm old enough that teachers told me we wouldn't always have one) just to punch in that "Volts X Amps = Watts" thing(tho with a battery you use 'amp hours' instead of just 'amps' because there is a limited supply in a battery vs a wall outlet...to measure this 'limited supply' we use time; as if a battery was drained over one hour, what would be the amp level for that hour....of course you can use it up faster or slower than that at different amp loads) I always think of it as 'voltage = rpm', then 'amp current = torque'(how many amps you can draw from the battery at once), and 'amp hours = range'; but that might not be exactly right...so when you calculate the watt hours you see the total potential power, that could be divided back up differently; slow long ride, fast short ride, or a bunch of hard accelerating quick rides, etc, however you need to run your bike that day....but you might want to optimize it in your build design for behaving one way(maybe higher volts for greater max speed) more than another(higher max amp current flow for stronger acceleration) or just all out range(lots of amp hours)
...the battery pack will be the most expensive part, and the part you will likely have to build your self...budget the most time, money, and thinking on that

-

I always kinda knew electric motor power was different than gasoline engine power
https://evmc2.wordpress.com/2012/04/06/electric-motor-hp-ratings-and-other-secrets-of-the-universe/
..so there is that...also I suspect it might be that a 11kW motor is better than a 15hp engine(even tho 11kW = 15hp about, at least in translation) because an engine just does power at a small peak(needing multiple changing gear ratios to make that usable) where a motor has power over a large rpm range...so there is much more area for the electric motor under the line of power on those graphs, so more total power tho no high peak?

so then now I'm up to here
https://evmc2.wordpress.com/2013/08/13/c-rate-and-c-rating/
...I should just get this guy's book asap...but tons of advanced stuff on his blog
(just when my brain was getting comfortable understanding some of this, I found his site to go back to brain buffer overflow)

pretty soon I'll be able to sound like I know what I'm talking about(even if I really dont) hopefully
....the people on here are really great and helpful...you just have to kinda know the right questions to ask besides 'tell me everything you know'....I mean; I'll answer a question like that, but I'll also mix in some stuff I don't know

good luck to you....and I always want to read what your ideas are for your eScooter, as there usually is something I can learn or borrow for my own project...heck, you might of thought up something new that no one ever has before, just because you didn't already know the typical ways to do this

are there good German hub motors you can get?...or are you looking at all the Chinese ones?

flo
28 March 2018, 1141
Hi there,
welcome to this forum.
I am from germany too, my project has been on hold for about 3 month now but as of today i started ordering parts again.
I am based near munich- where are you?
greets

flo

Flatout
05 April 2018, 1216
Wow, thanks for the warm welcome.
I'll read up on the links you provided T Rush, thanks.

I'm also from south germany but near freiburg. :)

T Rush
06 April 2018, 0453
what ever happened to the Bosch motors?....I came across this video the other day and could only find their bicycle conversion petal kits


https://www.youtube.com/watch?v=4k5TDZ6irG4

Richard230
09 April 2018, 0621
Coincidentally, my oldest granddaughter will be completing her college studies in Germany at the Fri University in Berlin this year. She is currently at UCLA majoring in German and Literature. I imagine that it will be quite a culture and environmental shock for her. It is already a financial shock to her family (no thanks to the decline in the value of the dollar). But she plans to obtain her degrees within just three years, so that will save a lot and help pay for the year of living abroad.

I guess she will be taking public transportation to get around Berlin, as I once paid for her to take the beginning motorcycle course, which she passed but she said that she didn't care for riding motorcycles, or driving cars for that matter. Oddly, her parents own and ride 6 motorcycles, including two Zeros, a 2012 S and a 2014 S, both with the largest battery packs available at the time.