# Greets from Croatia, need tips :) and a lot of advice



## unionthug (Jan 21, 2011)

I'm surprised there are no post on your questions, i to am looking at building a electric bike i will keep watching your posting to see if anyone responds


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## kek_63 (Apr 20, 2008)

Search for posts by "Crodriver" - he has converted the most amazing BMW. He will know exactly what is available to you - a fellow Croatian.

Keith


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## ZX-E (Aug 31, 2009)

Well since nobody seems to be biting on this post, and I'm an avid cyclist, I'll give this a shot.

I wasn't sure if you wanted to use mountain bike tires or road bike tires, so we'll go with something in between. let's call them cyclocross with knobby tires, which is _hopefully_ what you're aiming for. Mountain bike tires have a rolling resistance coefficient of about .025, while a road bike tire's rolling resistance coefficient can be as low as .005 on nice flat pavement.

Let's assume these somewhat educated guesses for your bicycle's characteristics:

Base bike weight: 25 lbs
Passenger weight: 180 lbs
Motor weight: 10 lbs
Battery weight 80 lbs: 8 12V motorcycle batteries 13 amp hours each 4s2p
Rolling Drag coefficient: .008
Frontal Area: 380 inches
Coefficient of Air Drag: .8
Rolling Resistance Coefficient: .008
Motor efficiency: .9
Electrical efficiency: .9

I messed around a bit until I found the 4 series 2 parallel battery configuration. It will give you about a 49 mile range at cruising speeds of 25 mph. You will have no problem reaching your goal of 30 mph top speeds at 48 volts. Finding a motor to match should be pretty straight forward.


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## ZX-E (Aug 31, 2009)

You should be looking at a 1000 watt motor (20 amps).


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