Kevin's Electric Bike

The material on this project was sent in by Kevin Felstead -- thanks Kevin!

From Kevin:

Just found the build it website. I have built my own electric solar-cycle with a layout I haven't seen before, the solar panels double up as mud guards, and I have made my own battery packs using 13ah ni-mh cells. The batteries are arranged in 3 packs of 11 each. Each battery pack contains 11 batteries taking up the same space as a Yuasa NP 12-12 this gives me a higher Ah rating ,higher terminal voltage and a lower mass.

You can see the layout from the photo . The PWM controller is mounted between the top two battery packs with a pancake motor mounted above. The power is transmitted through a toothed pulley belt + belt tensioner to a friction

drive. On full charge it will do about 25 mph probably illegal in UK which drops to about 22. I have done about 150 miles on it and reckon it does 12 miles WITHOUT pedaling. What do u think? Regards

Kevin Felstead.

You can email questions to Kevin: azzconcepts AT btconnect DOT com (Change the AT to @, and DOT to a period)

More info ...

Kevin provided the following additional material that might help those who want to build a similar solar bike:

Hi Gary ,
I am a one man electronic & mechanical design and manufacturing company (A2Z concepts ltd ) . Fortunately I rent a small workshop above an engineering factory and have access to many trade accounts and resources.

The bearing housings and tensioner linkages were made to my specifications for a robot i am building .

The pulleys were obtained from Farnell in one and a couple were modified to make the friction wheel (outer sleeves removed) the wheel on its own led to slipping in the wet and tyre ware and was then modified with strips of toothed belt glued to the pulleys, first layer engaged with the teeth ,second layer glued with teeth facing outwards as seen in the photo. This design works well!.

The belts came from RS components and so did the speed controller, but was modified to cope with the higher voltage (up to 48 volts) of the 33 batteries type 1FM13-0 in series. Four 300 WATT Mosfets were used in the output stage + a couple of resistors to adjust the cutout voltage to protect the batteries from over discharge .

The first battery pack was put together by me soldering the tags together and using hot glue and insulating tape. Note the tags supplied needed to be thickened by copper wire to cope with a current demand of up to 30 amps -- other wise they will heat up in use. I also fitted two 10K ohm thermistors at either end to monitor charging if required as part of the charging circuit. The other two battery packs were made by allbatteries (UK) ltd to my spec and the plastic ABS sides were glued together and made by me. Terminal posts were fitted to the lid and separated from the battery pack.

Much to my annoyance I couldn't buy a battery charger for my bike and had to build my own ,charging for 3 amps at 5 hours will fully charge the batteries from flat but care must be taken not to overcharge (need to look at charging spec on NI-MH CELLS for further details).

The solar panels were made in U.S.A , Model # 891 TGN 500-12 (9WATT 18VOLT 500mA (MAX Isc) These are made from tempered glass and are wired in series providing 400ma under full sunlight. My original bike used two np-12-12 lead acid batteries and the solar cells were mounted in parallel and fed into DC-DC Converter module Recom RP30-2415DEW.
DO NOT use light weight flexible PVs as any vibration is transmitted to the centre and they lasted about a week (costly mistake -- ouch)

The pancake motor was obtained from RS components and was rated at 28 volts. A higher voltage version was obtained from PML Flight link ltd (Trade only) using rare earth magnets. It made a strange noise and a carbon brush snapped in the middle . The company would not make me a rare earth magnet version in the 28 volt range (I don't know why). The defect was a blessing in disguise as the version I made from the two halves has served me well, even rated at 28 volt it has lasted me 150 miles so far. I am continuing to improve, test and modify. I hope this is of some use regards

Kevin F

Gary 2/7/07