Stage 1: First Serious Test

Well, I've already broken some guidelines. I did pay $0 for the alternator and the battery, that's a major component of the expense of this project. But in order to drive the thing, I needed a belt, a long belt. It had to be up in the neighborhood of 83" and be able to fit in the skinny little pulleys that were stock on the alternator. Getting a free belt didn't seem very likely to me so I decided to just choke down the cost. After describing what I needed to the dudes at Pep Boys, then explaining what I was building out of the alternator, and how I was not actually crazy (not sure if they bought that one from the looks I got), they helpfully sent me to Napa, where you can get get belts for ride-on lawn mowers and other machinery type equipment. The guy at Napa was very apologetic that they didn't have an 83" belt in stock, and hesitantly offered me an 84" belt, I told him that the precision of the length was not that important since the machine it was for, hadn't been designed yet! The $25 cost was actually covered by some earmarked cash I got for Christmas. The expensive part was the wiring bits and bobs I got at Pep Boys. I got a few rolls of 10g and 14g wire ($5 a piece), a couple switches ($4 a piece), some marine battery clamp terminals ($4) and several boxes of wire terminals in various sizes and gauges. This added up pretty quick. I will only actually use a fraction of the wire and terminals, but if I was going to wire cleanly and for the long term, I needed to source these. So oddly enough, I spent more on wiring parts than I did on the Battery ($0), Alternator ($0), and Belt ($25), combined. The devil is in the details, as it were.

Next came the base. I needed to firmly mount the alternator on a tensionable hinge. Using a couple small piece of scrap plywood and a scrap 2x4, I came up with a mount that would butt up against my existing stationary trainer, would use the weight of the battery to keep it down, and a turnbuckle to keep tension on the belt. Luckily my alternator has an integrated mount designed to be a hinge for tensioning, so this was actually pretty easy. I first tried to use just the weight of the alternator to keep tension, but quickly found that this was no good.

It resulted in voltage spikes and drops as well as extremely uneven resistance at the pedals in some preliminary testing. The addition of the turnbuckle was key.

So with the base unit pretty much in place, I wired everything up. I used the wiring diagram from P2cycles.com as a guide to put all the connections in place, my thanks to them for providing such a clear diagram. Hopefully, I will eventually have all of the trick connections in place down the line to measure power and have the bar mounted switches as they did in their very sexy implementation.

Then it was time for a test. As an afterthought, I wired up some leads that would allow me to more easily read the multimeter while pedaling, and also hooked up some leads to an inverter, to which I plugged in my iPod. The iPod's battery was completely flat, as a bonus.

Here's the test:

It's a go! I was able to get voltages up around 14.4v while pedaling. What you don't see in the video is my heart rate, which I do have a readout on my handlebars for. Unfortunately, my pulse quickly hit 180, which is basically my max output. I was only able to sustain a cadence >90rpm for about 5 min, and I was completely juiced at the end. I think this is the result of the car battery being almost completely flat, I initially charged it just enough to be able to power the alternator's field. I think the voltage sensor in the alternator is detecting that the battery is low, and putting a heavy field in place to charge up the battery. I'm not sure about this and I need to do a little more research. While I look into it, I'm going to charge the battery up to a higher level, just in case.