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Friday, December 4, 2009

Batteries, Bikes For Parts, etc

300+ Li-Ion 18650 batteries arrived a few days ago, courtesy of an unbelievable deal on Endless Sphere, for batteries intended for another cycle EV but not used. They are pulls from new/unused batteries for medical equipment, so they are still "recycled" parts. They cost me my grocery money for a month, but I managed to survive, and there won't be another deal like that anytime soon.

Most of them are tested good; some are known not good, which is ok; they can be used for physical experimentation of assembling the packs, among other things.

They're essentially the same as what you'd find in the typical laptop battery, so they don't output a lot of power, but they also don't weigh much. All of these batteries together only wiegh a hair under 30 pounds, which is only 2/3 of the weight of my current 36V 17Ah SLA pack. Since these are 2Ah 3.6V nominal each, that's roughly 36V 60Ah, assuming a 10 series / 30 parallel pack. Even if less turn out to be good than expected, that's still far more than the SLA pack for much less weight.

The challenge will be to build them up into packs, and to build a BMS for them to prevent over charging and discharging them. These are the type of batteries that *can* burn when damaged, so they need to be treated with care, so I would prefer not to run them without some sort of warning system, even if it does not automatically cut off power but only alerts me.

Next, I found a couple of bikes for $5 for both at a yard sale:

A Schwinn Traveller 12-speed, with the next-model-up Suntour shifters/derailers from the ones I had gotten off the PanWorld bike before, and used the rear derailer from on my CrazyBike2. The derailer is something I've so far only seen on these Suntours, where the cage is split in the middle so you can easily pull the chain thru it, not requiring a chainbreaker or master link to undo and making it very easy to take out and put in the rear wheel.

The crankset is a square-taper, and in fact came in handy shortly afterward when I hit a bump when I was almost home that knocked my pedal chain off, which was then pulled by the motor and caught on the frame, bending the pedal chainring on the dual-ring set for motor/pedal transfer to the rightside drivetrain. Not as badly as the one previously destroyed by motor torque, but bad enough that I would rather replace it than fix it. So I used this one; I left the crank on it, though, since it clears everything fine.

Then there's this Huffy Sun Dance, with Shimano parts

One-piece cranks, nothing really stands out except the rear derailer is a little different cage from what I've seen before, and it uses a round reflector in the front wheel (none in the rear wheel).

I haven't investigated yet, but that little screw-down bit on the cage looks like it might flip open to let the chain pass out similarly to the Suntour one above. I wish modern derailers were made that way, as it is a very nice feature.

Some pics of the CrazyBike2 as it was when I started this post (it's changed significantly now, as you'll see in the next post)

The wiring still looks like a mess, and I'd like to build a battery cover to put around the whole center section.

Haven't done that before for various reasons, and now I don't want to because I am going to build those new packs, and they may need a different shape/size box.

This is the "new" 2-ring crank off that Schwinn, replacing the one I bent the pedal ring of.

By chance it happens to be the same tooth count on both.

This is a "dashboard" shot, with the speedometer/PDA, and the power meter to it's right.

The wiring as it was then. Similar now, except I added a plug for each end of the meter, so I can swap it around to measure charging power, then put it back to measure discharging.

The new cables donated for the purpose:

I ended up not using the red ones because they don't connect to any others I have; they're keyed differently. Rather than modifying them, they'll be used for a different interconnect on the bike later on for a safety switch, so it can't as easily be bypassed.

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