Electric motorcycle

In addition of the solar heater project I've been playing around with idea of DYI electric motorbike. Actually I've had this idea for long time now - maybe ten years - and it is possible (even likely) that I'll never get around doing it, due to component sourcing issues (mainly the battery pack), but planning is kinda fun nevertheless.

This would be strictly for nearby city cruising. Total driving time some 60 minutes or slightly more (at inner city speeds), top speed maybe 120km/h or so.

So first some research about required power. From some site I found out some information for scooters and power requirements there. It turns out that about 100km/h should be doable with just 10kW power. If I were to limit speeds above 80km/h to short duration only, even smaller engine would do - 8 or even 6 kW might be enough. This would not be fast bike, though, so maybe I should target about 10kW at first.

Then the battery voltage. I thought about 120v pack first, but currents required at high speeds (maximum power) would be uncomfortably high. But for now I go with that figure.

For the frame I was thinking about getting old Suzuki GS500 frame (which happened to be my first bike - light and nice to drive, although not great for longer cruises due to vibration caused by small-ish 2-cylinder engine), but those, too, tend to be "a bit" expensive here at the moment. But I keep that as a starting point yet.

Now, the engine. At first I was thinking about using permanent magnet DC motor for this, but it turns out that suitable motors are damn near impossible to get, at least in sane prices. So scrap that idea.
Then I read some more about 3-phase induction motors, and they seem like suitable alternative with proper control scheme. Naive control implementation will be horribly noisy (EMI-wise) but for a hobby project - and with loads of shielding - that might be okay. 120v Y (star)-connected motors are also available quite easily, although I will need to up the battery voltage for that; 120v AC is very different than 120v DC.

Then the battery pack. This turns out to be hardest part actually. Full, ready-made packs aren't really available, and if they are, they're too big or shaped so that they won't fit the bike frame. I would have to go for full DIY-pack, individual batteries, with all the protection, control and charging electronics included. While at this point I am fairly comfortable with high voltages involved, the charging and general safety is very different thing. And this, unfortunately, might be problem that will kill this project. Especially since things like zero motorcycles are already available, although the price is a bit high-ish; nearly 20k€ here ... But I suspect my DIY bike might easily be equally expensive, in the end, even if I weren't calculating price to work required.

But hey, even if this idea will never be realized, it's still fun to think about all the issues and solutions involved. And like always, some of the ideas will almost certainly carry on, to upcoming (possibly more profitable) projects.