You dont talk fof terrain? v relevant.
Your hardest, heaviest and most expensive choice will be battery. Too long a story for here,but personally, lifepo4 is a no brainer.
8km is a snack. even a 5ah 36v would do.
yes, assume there will be times when you not only dont wanna pedal, but that you cant pedal, even on hills e.g u r carrying an awkward load - it happens. even a broken transmission neednt stop u with a hub drive.
I like the simplicity of a front hub also. I cant see much if any torque effect from a hubdrive & way simple to swap to another bike.
If you go the hub route, seriously consider the "xinghua" or whatever dual speed hub. 2 gears is not bad given electrics torque. an impressive unit i hear.
less traction than rear traction is hardly an issue on a bike.
regen is useless except as a brake (which only bad riders need much), forget it.
sounds you are eu rules in sweden, which usually makes stealth an issue - dont look or act as if you have more than legal power.
250w would do probably only if a geared middle drive motor. In fact, the only vaguely legal general use bike for eu rules is mid drive. Hubs would do for flat river plains, but u need pedals too for any decent grades. Still, spoil u self, get 350w & cheat a bit, they need never know. They are the same motor usually, and the same looking controller.
having decided, NB , u must have a battery that can provide say, 350 watts. a normal 10ah 36v li-ion battery, can only just provide that, and only for a few minutes while full, then weakening, and the last 20% of charge is useless.
a 10ah 36v lifepo4 pouch cell battery can provide a steady 350(/360) watts for an hour, until fully empty. It can also provide 700 watts for a half hour if u choose.
a handy guide measure i saw, is it takes 100 watts for a roadbike to maintain 25kph on the flat. each extra 5 kph adds 100 watts to power usage.
so 25-30kph seems a sweet spot windwise, irrespective of bikes wind resistance.
assuming 25kph & flat, your commute should be ~20mins at lets generously say 200w per hour of the 10ah batteries 350watt hour, ie, ~70watts of the 350watt storage total - 20%.
so you could go smaller, but not with li-io (limn to be more precise - 18650 cells normally). As above, it can only provide a measly 175 watts if u r lucky. a 5 ah lifepo4 tho, can provide at double rate for half the time - its 175watt total can be delivered at a rate of 350/360 watts for half an hour. if u have used 70watts as a bove, you u are still more than half charged. You will save some money and about 1kg in weight.
the numbers matter less than the logic. think in trems of how much time using the equivalent of maximum power on my motor, do i think i need for my purposes. Too hi & u waste money and weight, too low & u have to pedal some, but a lighter bike.
they relate also to the guy suggesting a 500w+ hub motor. I can imagine overpowering so u dont need gears is a nice feeling, but its bound to be inefficient (all motors have preferred rpm bands), u need a heavier/dearer battery, the motors are very heavy (airfreight cost?)
My personal repair kit is the backseat of a cab. So For me, an easy qik release front wheel is a bonus. Not sure how hub front motors alter this.
HOWEVER
Dude, if u sat down and really figured what that car is costing u, in all sorts of sly ways - we just get used to forking out - u can afford to act like a millionaire - even an ~expensive factory one is a cost effective bargain. if u know its a no brainer, and i think you do, just place value on your time and buy the best tool for you.
i started a thread on a $1500US bike thats perfect for eu rules & I own and love & got mostly hate mail
for my trouble
its called the worlds best ebike nobody ever heard of, or similar - recent
