It often is said that the Bionx system is closed and cannot be modified. Last summer I bought a 250 watt Bionx kit used and succeeded in upgrading it with externally mounted battery booster voltage packs made from DeWalt A123 batteries.
Briefly, I opened the battery case, found the main wire leading away from the battery, cut it and soldered in new wire which lead out of the case through one of the bolt holes to the additional battery pack which was mounted on the top tube with a velcro strap.
The original NiMH Bionx battery started at 27 volts with a full charge and I conducted test runs with up to 38 volts. I am a reasonably fit cyclist and my cruising speed went up from 18-19 mph to 24-25 mph. It may not sound like alot, but it was a very noticable difference. I have a photo but nowhere to host it, if someone would like to post it, I will email it to them.
I could have easily replaced the Bionx battery with A123s, but had to turn my attention to other things. I imagine the 36 volt Bionx motors could also be upgraded in the same manner, and cruise speed (conjection mode on) might go from 23 to 28 or so.
When I hit the highest voltages, the motor began to cut in and out during cruise. I could get reliable performance at a cruise speed of 23-24 mph, though.
Opinion mode: Riding a high performance and silent Bionx bike is an experience all on its own. Why Optibike use a throttle is beyond me. Its like using an old computer with a bad interface. It isn't a motorcycle, it is a bike, and long ago the bike interface was refined to pedal harder to go faster and steer and brake with your hands.
I also hacked the controller and made tiny tactile switches which were mounted underneath my handlebar grips and put the battery in a backpack. The switches were not visible at all and could be activated with my right thumb without moving my hand from the grip.
Overall, the experience of flying along roads at 3am under a full moon with this system reminds me of the quote- "the future is already here, it's just not evenly distributed."
Perhaps someone has already or will make similar upgrades to a 36 volt system, taking it up to 48 volts or so. That would be one rocking ride with speed and torque.
Safe riding to all!