[singing] Bicycle, bicycle

For years now, I've wanted an electric bike. I guess it's like the whole Power Wheels phenomenon from when I was a kid. It's just fun to make something move under power that's not your own.

Now that I'm doing for a living what I've been obsessed with since the age of eight, I can get into my craft a lot more without it being a pastime. Hence, my new project.

I'm kind of a treehugger at heart so I try to be environmentally conscious as much as possible without being penny wise and pound foolish. When I saw that a bunch of defunct big rig data recorder boxen were going to scrap, I jumped at the chance for salvage. The expensive satellite modems and venerable flash drives were saved, which was a good thing, but that's not what I was after.

Those particular units used a backup battery inside, one that's rated at 9.6VDC with a capacity of 2100mAh and uses the wonderful nickel metal-hydride technology in AA cells. Interesting to think that such a capacity would have required rather exceptional C cells, were it nickel-cadmium technology like most rechargeable cells were when I was a kid.

I've managed to salvage a total of sixty of the packs and a few charging boards. Far better they be reused than go to a recycler. I can't imagine the batteries would be easy to recycle, much less make the recycler any money.

Although it's unusual to power anything big off of so many cells, I find it kind of funny. It's like the electric cars that use hundreds or thousands of cells in their battery packs.

After careful consideration, it looks like I'll be keeping the packs as they are and just linking them up. I will be running four packs in parallel for each battery bank and three banks in series for 28.8VDC nominal with 8.4Ah capacity for each battery brick. Each brick will have a rather hilarious 96 cells inside.

Each battery brick will have a relay to disconnect each bank for charging. I will be using the charge boards I salvaged, but I need to see if I can bump the charge current up from the .5A setting they currently have. Even at four times that, I'm still in the C/4 range on charge rate, which should be fine much of the time. The charge boards, luckily, run off of a standard 12VDC supply, but appear to have a wide range of input. That's freaking easy to come by, even with solar. I'd really like to see a solar charger for this system.

The motor of the bike hasn't been decided on just yet. There's a company selling motor kits on ebay out of Seattle. I like what they have, but there's still the question of fit and whether I want to give up my three speed front gearing for a single-speed freewheeling sprocket.

In the meantime, I do have a test platform for all of this. A year ago, I bought a Pukka mini-bike for $50 and have had it in storage almost ever since, due to the lead acid batteries being expensive and the fact I look lame riding such a small bike. It will make a decent test bike since it's a 24V system and has a decent motor. I'm sure I'll be posting updates about this project a lot. Now I just need to figure out photos.

I plan to build at least five battery bricks and two charging systems. The idea is to have the ability to keep one brick torn apart for repair while one set is installed on the bike and another is charging. The two charging systems will allow two bricks to charge at the same time. Maybe I should build more than just two, in order to have a spare.