Tuesday, 22 April 2014

Resurgat Forza

My first electric bike was a big, sturdy Forza. It has a 36 volt motor, and it went well. I used it for about three years. But it suffers from a major drawback - it isn't a folder. That means that A) to carry it on the car, I have to put on a bike carrier, and while that's on, I can't open the rear. And B), I can get a folder through the kind of stile that's a metal circle and a metal gate, without having to lift it. Quite a few stiles are like that, so that's a big plus. So the Forza fell into disuse as soon as I got my first folding bike.

Recently, I got it out, charged up the battery, and tried to run it. But the battery is now eight years old, and doesn't hold much of a charge; when I gave it full throttle, the BMS (battery management system) decided that it was all too much for the battery, and cut it out.

So I put it on Ebay, with the proviso that the battery needed replacing, to see if someone else could make better use of it than me. The best offer I got was £100, and it's worth more than that as spare parts; the motor alone is worth £100.

So it sat in my bike park, while I worked on other bikes, but then I thought, "I bet I can make this bike live again". I got a 12-fet Infineon controller (I like those because they're programmable), and stripped the bike down. I took out the old controller, the old throttle (it's a left handed twist throttle, and I've become accustomed to a right handed thumb throttle). I took off the battery carrier (because I now carry batteries in a pannier). I stripped off the front and back lights, because I use a head torch for a front light, and a removable silicone light for the back.

And then I found that I couldn't connect the hall sensors on the front wheel, to the controller, because I didn't have the right sort of connector. So I went on to Google, did a lot of research, found that what I wanted was a "six way 2.8 mm" connector, and ordered one from a UK company (they usually arrive faster that those ordered from China). I also ordered a handful more of the six-way, three-way and two-way connectors from a company in China, because it's always annoying to need a connector that you don't have.

The connector arrived today, as well as a centerstand. The centerstand didn't fit, because when I installed it, the legs fouled the chain; I could maybe deal with that, but I'm fairly happy with the sidestand I already had. The connector, however, did fit, just fine. So I wired everything up; three-speed switch, thumb throttle, halls, phase wires and battery wire. Then I connected up 10S of battery (which gives a nominal 37 volts), and gave the motor some power. It hummed, and reluctantly moved a centimeter or two.


I got out my bike tester, and verified that A) the halls are connected correctly, and work, and B) the motor windings are fine. Um.

So I had a bit of a think, and I decided that maybe the phase wires need to be connected differently. I had connected yellow-yellow, blue-blue and green-green. But there isn't actually any kind of standard for the labelling of these. As you can easily see, there's six possibilities for connecting these three connectors. The second one I tried encouraged me a lot; the motor made quite a lot of noise, and turned, although slowly. And, of course, it was the sixth combination that I tried, that actually worked! And even better, the motor rotated the way I wanted, tending to drive the bike forwards.

So I installed a handlebar voltmeter (which tells me how much battery I've got left), tidied up the wiring with cable ties, waterproofed the connections using sections of old inner tube, pumped the tires up to a good pressure, and took the bike out for a test run.

It performed like a thoroughbred; it was going better than it had when it was new! That's partly because Lipo batteries are better at delivering power than the LiFePo4 that commercial bikes use, and partly because the Infineon controller is way better than the el-cheapos that you get in most commercial bikes.

Then I weighed it, and that was a big surprise. I was expecting it to be heavier than any of my other bikes; if you look at it, it just seems a lot more substantial. But it was only 49 pounds (without batteries), less than any of my other 26-inch wheel bikes. Only the smaller 20-inch wheel bikes are lighter. It's made of aluminium, that's why it's so light.

So I mended the thing that attaches the front mudguard to the bike (that's been broken for a long time, and was held on with string - instead, I made a fishplate so it could be attached properly).

The Forza, therefore, is bike.6. Hopefully my bike habit is now sated.

I'll use it for local trips, because when I buzz up to the local shops, or whatever, that won't involve putting it on the bike carrier. I can just wheel it out of the bike shed, clamber aboard, thumb the throttle and whoosh!

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