Hard to interpret text over the internet. BF may have been telling you to take a hike, but he may have just been telling you that there are few people here that can really answer your questions. Elmoto really is the best forum here for DIY ebike design, but IMO there's no harm in discussing here. If I'm wrong then please explain what the purpose for the off-topic forum is, because I'm missing it : o
Electric bikes right now are a toss-up between flexibility and reliability. If you buy a pre-packaged bike - a Zero or a Brammo - then you get a well-assembled package, a well-tested powertrain, and often better / cheaper technology than you have access to if purchasing as an individual. You also get some measure of increased reliability, though as we've seen with the Zero controller glitches, well-tested doesn't mean error-free. Because you typically need to use an electric powertrain for 8-10 years to get good use out of it, you need a bike that's reliable for 8-10 years.. and IMO building and designing your own bike won't get you reliability for that period of time.
Building your own bike is great because it gives you the flexibility to build exactly what you want. If you only need 30-40 miles of range but you want 5s 0-60 times, you can build a 10C 4-5 kWh pack that will give you that. If you want to build a LSR bike, you can mod a Zero and do 100 mph or build your own Lightning bike and do 218.
One option might be to buy a used electric bike and replace the controller/motor/batteries, depending on what you want. 70 km = 44 miles, means you should look for a used 4.4+ kWh bike. That pretty much means a used 2012 ZF6 Zero. 5.6 kWh battery pack is rated for 10C burst = 56 kW, reconfigure the battery pack from 18s4p 65v 80Ah to say 24s3p 88v 60Ah or 36s2p 130v 40Ah .. then pick a motor and beefier controller for faster speeds. Once the 2013 bikes come out you should be able to pick one up for cheap. Older Enertia could work, but you'd need to replace controller/battery/motor.
Reconfiguring the battery pack means you need a new BMS and charger. Maybe more trouble than it's worth. Wish they had come with a higher voltage from the factory.
Basically, if you want to build your own bike, you should do it. If you don't particularly want to build your own bike, but the factory bikes aren't cutting it, I really would suggest waiting rather than building your own. They're getting better and better each year.. even if those improvements aren't exactly coming on a predictable schedule.
