Custom electric bicycle builds (DIY)

To the concern of many people; i think that we can all agree that buying a car is substantially different then buying, say a new computer. Both are investments but the price and the means of use are very different. So what do we do when something new comes along that could fit between the two; the means of transportation, but the cost closer to a computer? Well the answer is simple; we shop around and see how we could get the most bang for our buck.

So far, BionX seems tb the most attractive choice for my needs.

Specifically the integration of a torque sensor in the motor with the controller - providing 4 levels of assist.

The only thing I'd want, if possible, is a more generic battery option.

Use of electric drill batteries as in Russ' "The ultimate Seattle hybrid bike" thread sounds sensible.

To wit:

- They're widely available, almost a commodity, so prices sb lower

- They're modular. 36v system, just keep adding batteries in parallel to get desired capacity

would it be more durable to have a sensorless motor design? just thinking it would be one less moving part...

My stretch bicycle project (Stretch-e-bicycle phase 1) is getting further along but I ran into a snag. I'm using a 48v crystalyte motor and it's wide enough to rub on the forks. The motor barely moves. Dang wish I'd noticed this before now. Good thing about the project is I've got the brakes sorted out and all the welding and stuff is done.

I'm looking for advice on converting my bike to run off 72 volts. My current setup consists of a nine continents motor with a 35A controller running off a 48v 20AH LiFePO4 battery. Is the best way to get up to 72 volts to connect another 24 volt battery in series? If so, how is this done taking into account the battery management systems? Do I need to match the amp hours to my existing battery, or does that matter? Should I be concerned with the power or current being drawn damaging the batteries?

Has anyone upgraded from 48v to 72v that can share their experience?

The LiFePO4 pack that I bought some times cuts out when pulling from a stop.
The bike never did that with the lead acid batteries.
I am assuming that the BMS is current limiting.

Has any one tried to add a super capacitor in parallel with the battery to help at take off?

I am wondering if the cap could hurt the controller some how by allowing current transients.
I wonder about saftey concerns.

Calculations:
Kinetic energy in Jules=(mV^2)/2 (m in kg, V in m/s)
Energy stored in a capacitor in Jules=(CV^2)/2 (C in Farads, V in Volts)
It would take 5kJ to bring the mass of the bike and myself up to 9m/s (20MPH).
No-load voltage is 48V (lets just say 50) and to keep a good strong acceleration, we dont want the voltage to drop below 40V. would store 5kJ in a 10F capacitor.

So, if I add a 10F capacitor, I should have enough energy stored in that capacitor to get me up to full speed. Once the load reduces, and the battery voltage increases, the batt would recharge the cap while I ride.

Any one try this?
The Caps are cheap these days. $50 for 100V, 10F

-Mark

This is a project that's been in the works since the beginning of this year, based partly on previous projects, partly on web research, but mostly on whatever I happened to have on hand when I started it, and what I acquire as I go along.

It's very functional already, but could stand serious improvement (most of which would require parts or tools I don't yet have).

I ordered some of their stuff to upgrade my ebike.
I blogged on it.
http://visforvoltage.org/blog/moveon70

Over all, I was not happy that the form factor of the motor was not as advertised, but on the other hand, the performance is really good, and the price is low.
-Mark

I have used controllers on bikes more than a few times. I have never really had one act hinky lite this before, so I thought I would ask to see if anyone knows what the heck it is doing.

I have a bike with a rhino drive, my own build, it runs a 24v 600watt brush motor. I purchased a 36 v 800 watt controller. The controller does fine most of the time, then just shut down completely for no apparent reason. It acts as though it is over heating or something. If I give it a rest, the controller will start working again.

I've been working on and off for a long time on a stretch bicycle I want to use for cargo (around town shopping etc). The bicycle frame is one I've had for a long time, bought it in 1997 to install a Zap DX electric assist kit on it. FWIW that wasn't my first electric bicycle, that happened in 1995 (also a Zap DX kit).