MiniCycle V2 and DethWhacker

A few weeks ago, MiniCycle V1 was completed and Tom, Shane, Charles, and I went to the garage to do some time trials. This thing is TINY. Due to impatience, we used the old battery from DethScooter, a 26.4V (8S) 4.4 Ah pack I built in September 2011. Also due to impatience, the battery was wedged into a space between the motor controller and the rider's crotch. Not exactly the ideal place to have a battery malfunction. Regardless of battery position and rider vulnerability, the bike had some killer initial acceleration (watch the video) but not a huge top speed, probably about 20 mph.

lol

Tiny and Chibi

Right-side-up videography by Charles Guan.

To fix the problem of the slightly lower than desired top speed, I built another battery pack that would a) go faster and b) fit better into the frame. The pack is 33V nominal (10S) and 4.4Ah. 

Please ignore scorch marks on negative terminal.

Couldn't find heat shrink big enough. Kapton tape and foam to the rescue!

Fits perfectly!

The bike was tested in the Stata Center basement and will hopefully do some garage runs later this summer with the wattmeter and right-side-up video camera.

And now on to the home improvement portion of our show post. Today's task: make the Black and Decker weed whacker a little less... awful. The stock battery was a 18v 1Ah NiCd that supplied about 10 minutes of underwhelming plant mutilation. Sometimes it cut all the way through the plant and didn't just knock it over... Sometimes. Regardless, the first iteration of DethWhacker (named as an homage to DethScooter) uses a 19.8v 2.2Ah battery and is actually kind of terrifying.

Scooter Battery Replacement

The original Deathscooter battery was kindly made for the Engineering Design Workshop by Shane Colton. Unfortunately, Shane was pressed for time, so he accidentally wired the battery backwards. We discovered this after we connected the motor controller to the battery and the connection exploded. The wires' colors were 'reversed' via heatshrink tubing, and two new deans connectors were soldered to where the old ones used to be. Oh, and the battery didn't have any balance wires either. This battery should not exist. And so in August I built a new battery pack (same specs: A123 8S2P 4400 mAh 26.4V) to replace the old one. On that fine summer day, I did everything except attach the connectors, which is, you know, kind of important.

2.5 months later, I finally got around to finishing the pack. The reason I hadn't done this sooner is that the battery pack that Shane built hadn't exploded yet, and was still performing well despite my extensive usage sometimes requiring multiple ~70% capacity charges per day. The reason I got around to doing it is the darn thing was sitting in N52 almost fully assembled, and I should really be using the pack with balance wires.

Alright here we go. The first step is to put these little tiny connectors on each of the balance leads and put them in a plastic holder so it can be plugged into the charger. A note for anyone trying to build their own pack: do NOT try to strip, solder, or do anything else to two balance leads at the same time. If you try to cut or strip them both at the same time, they will short together on whichever metal cutting tool you have chosen for the task. You and your pack will not be happy. Strip one wire at a time, solder the connecter, crimp, place in the holder. Repeat as necessary, in that order.

Soldered the deans connector onto the main wires. Pack is operational.

- black white brown backwards rainbow +

And we have our fully operational balanced pack!

Looks like we're done for the day. NOPE.

The pack doesn't fit inside the battery bay on the scooter because the wire sticks out the top instead of the side on part of the pack. The segment of wires in front of the conveniently (and accidentally) placed cinnamon toast crunch box needs to be moved from the top to the side.

Carefully slicing open the pack, I am terrified of cutting a wire or worse, shorting two wires with my knife blade. Luckily neither of those things happened.

Black wire was pushed over to the side, and the pack is ready to be sealed up. Wait...where's my duct tape? Crap. Well, floor mate Julia to the rescue... 

Probably the most colorful pack I will ever make.

It fits!

And so Deathscooter was made a bit more colorful. 

Note: I will still not ride this machine until I get a new front wheel, which is in the mail as of tomorrow (hopefully).

Batteries EVERYWHERE

Today the parental units visited me for dinner. They also dropped off about $50 worth of batteries. For the record, I did ask for batteries, I just didn't realize they were to be bought in bulk at Costco. Adding these to my current collection, (along with their incredibly space-inefficient packaging) I found my desk drawer completely filled with Duracell.

Batteries EVERYWHERE

And so the mission began to create a storage system. Using AutoCAD I designed a battery rack that lays flat in the drawer and organizes the portable power sources very nicely.

Magenta is the default color for cutting on the Epilog laser. 

I'll hopefully get around to cutting and assembling this soon.