Electric Bikes – where are we up to?

Well, it has been a long slow learning process but the end is in sight. In fact Lynn’s bike is fully built and ready for the road with the exception of an acceptable battery configuration. As mentioned before, Lynn is not tall, and has a 700c wheeled bike. The original battery was 4 cells by 3 in a “safe case” to be strapped to the top of the rack. This turns out to be too hard for Lynn to swing her leg over, and also makes the bike a bit top heavy. So her battery is currently being rebuilt into the original idea I had, which is a “saddle pack” – a rigid battery case with two packs of 6 cells arranged to be carried down each side of the pannier rack. In fact each pack of 6 is arranged in an “L” shape (see the first photo), being two cells wide on the short leg, and 5 cells long on the long leg. On top of the rack, this leaves a 60-70mm gap between the two sets of cells, room for the BMS and connections to be laid out neatly inside. The fourth photo shows this, but not very neat at the moment, and there will of course be a lid on the box!  It also means that the two sets of cells have to be connected together, between cells 6 and 7, but a hefty piece of cable will sort that out!

The case is made out of 10mm foam board (the end “U” shaped pieces, the white bits in the photos)  and 4mm ACM (Aluminium Composite Material) for the rest of the flat panels (the black bits). Screws, glue and some 20mm aluminium angle extrusion will make it strong. and either a couple of layers of fibreglass cloth and some resin or a nice wrap in carbon fibre look-alike vinyl will make it look nice

The pictures also show the other major change to the layout. The controller was going to go in the frame gap, but on this bike, it just would not fit neatly, so we bought a Topeak large aero wedge saddle bag (strap on) which fits (only just) between the seat, rack and mudguards, and takes the controller and what little spare cabling there was left.

To get to this point was time consuming to say the least. The original controllers, while they ran the motors Ok with a throttle, just would not work with the PAS we had, so we have tried various combinations of PAS (the 12 magnet type) and LED handlebar control units. In the end we had to buy new controller units with LED control units that matched. The good thing about these changes is that the whole handle bar configuration is now the throttle (which is on the left on both bikes) and an LED control unit, which controls the power setting and the “6kph” function and is also the on-off switch for the system.

The 12 magnet PAS units still did not work, and the 5 magnet kind did not fit on our bottom bracket/pedal crank combinations. So new brackets were made for the 5 magnet PAS, which attached to the seat tubes just above the bottom bracket, and hold the Hall Effect units in just the right place. Some experimentation with direction of placement and magnet discs was needed, but the solution is reasonably neat and secure.

My bike is assembled to the same point, and will eventually get the same battery layout, but currently it won’t go! I have some diagnostic work to do, hopefully it is just a connection which is not good, but I have a feeling it is the controller. So I may be buying our 7th controller soon! I know the motor is OK, I connected it Lynn’s system and it goes fine. When I have the wiring identical I will swap the controllers and try it from there.

Even though my bike is much roomier, it will also use the Topeak saddle bag container for the controller, as it looks really neat on Lynn’s, and I am trying to keep the bikes as close to identical as I can. Being identical means that various units can be swapped between bikes for diagnosing problems too.

Here is a picture of each bike without batteries, not long to go now, but as winter is well and truly on us here in NZ (we had a frost this morning!) I will continue to take my time and get them right! More soon.

Photo0105 Photo0106

Posted in Electric Bikes

Leave a Reply

Your email address will not be published. Required fields are marked *