audrey xie
not a jack of all trades, nor a master of one. i prefer just being a lazy bum.
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When it doubt, Dremel it out — EV Moped Conversion pt. 3

The real purpose of the scientific method is to make sure nature hasn’t misled you into thinking you know something you actually don’t know. (Robert Pirsig, Zen and the Art of Motorcycle Maintenance)

Lithium ion batteries are expensive. Fortunately, my brother found one in a trash can at school and gave it to me when he came back to the Bay Area (thanks gregory!). But there were a few problems. First, the battery was not charged and I didn’t have the charger. Second, there was a lock on the battery for turning it on and off, and I didn’t have the key. Third, and most importantly, I didn’t know if the battery actually worked. Maybe it was in the trash can for a reason, right? Either way, I would have to solve the first two problems before being able to solve the third.

The charger had to be ordered online and would take some time to arrive, so I started off with the issue regarding the key. I wanted to either remove the lock and replace the on/off mechanism with a large button or remove the pins from the lock so that it wouldn’t require a key to turn. In order to decide which path I would follow, I first had to take a closer look at the lock. Thus, ignoring the large sticker on the front saying, “WARNING: DO NOT DISASSEMBLE,” I disassembled the battery.

I thought that process would be fairly straightforward, just unscrew the bolts until the battery falls apart. However, today wasn’t my lucky day, and I soon realized that there was a metal rail running along one side of the battery like a spine that held everything together. Worst of all, there was no easy way to take it out. I was getting impatient, so I brought out the trusty Dremel Micro outfitted with a cutting blade and surgically removed the metal piece. Lastly, I very carefully cut the wires in the battery to fully separate the part containing the lock. Since I didn’t want to make the mistake of soldering the wrong wires together when I reassembled the battery as they all looked very similar, I labeled the corresponding wire halves by making different shapes with electrical tape and taping those shapes to the wires. Black rectangle goes to black rectangle, red triangle corresponds to red triangle, so on and so forth. Looking back, I would like to applaud myself for this rare moment of forethought.

Now came the fun part, messing with the lock. A couple years ago, I had a very brief obsession with watching lock picking tutorials on Youtube. I didn’t want to do anything illegal, so I never really got to apply my knowledge. However, this battery gave me the perfect opportunity to see if I actually gained any skills from watching those videos. I decided to go full Hollywood, and use bobby pins as my lock picking tools. After fiddling around for two hours, I finally gave up. The lock was not picked, and I suffered a big blow to my ego and confidence.

When in doubt, use the Dremel Micro. I cut out the pins, and at last, the lock was able to spin freely. It turns out that this lock was more complex than I thought. Instead of only having pins on one side, there were pins on two sides of the lock. Therefore, in order to pick it, you would have needed to use two bobby pins on either side, three hands, and very good timing.

Now that the lock was no longer a lock, it was time to reassemble the battery. I began by soldering the wires. There’s nothing much to talk about, just melt the solder, stick the wires together, and heat the heat-shrink tubing. Well my dad, with his infinite electrical engineering experience, said that I should probably fray the ends of the wires and shove them together before soldering for wires that carry more current. It’s hard to explain, either way, there are pictures below if you want to try this technique.

The charger hasn’t arrived yet, so the next update will probably also be about batteries.