An Interview with Tesla Battery Hacker [wk057]

We covered [wk057] and his Tesla Model S battery teardown back in September. Since then we had some time to catch up with him, and ask a few questions.

You’ve mentioned that you have a (non hacked) Tesla Model S. What do you think of the car?

It’s the best car I’ve ever driven or owned, period. Not to get too into it, but, I love it. I’ve put almost 20,000 miles on it already in under a year and I have no real complaints. Software feature requests… but no complaints. After almost a year, multiple 1700-miles-in-a-weekend trips, and an overall great experience… I can never go back to a gas vehicle after this. It would be like going back to horses and buggies.

A salvage Tesla Lithium battery had to be expensive compared to a Lead Acid setup. What made you go with the Tesla?

Actually, if you consider that the Model S battery is already pre-setup as a high-capacity pack, contains the wiring to do so, and the modules are much more energy and power dense than any lead acid battery bank, it’s actually almost cheaper than a comparable lead acid bank and all the trimmings.

I haven’t officially weighed them, but the modules from the Model S battery are roughly 80 lbs. 80 lbs for a 5.3 kWh battery is around 15 lbs per kWh, which is impressive. For comparison, a decent lead acid battery will have a little over 1 kWh (of low-rate discharge capacity) and weigh almost the same.

Also, the Tesla pack is much more powerful than a lead acid bank of the same capacity.
Generally a lead acid battery bank would have a capacity that would only be realized with slow discharges, so, 1/20C. Much over that and you sacrifice capacity for power. 1/20C for an 85kWh pack is only 4.25kW, barely enough for a central air unit and some lights without losing capacity.

Now the Tesla pack can be discharged (based on how it does so in the vehicle) at up to 3.75C for short periods, and at 1/2C continuously without really affecting the overall capacity of the pack. That means I can run 10x more power than lead acid without a loss in overall charge capacity. Leads to a much more flexible battery solution since the loads will, in reality, always be so low that this will not even come into play with the Tesla pack, but would almost always be a factor with lead acid.

Charging is also somewhat better with the Tesla battery. Charge a lead acid battery at a 1/2C and it will boil. Charge the Tesla pack at 1/2C (42kW) and it might warm up a few degrees. Oh, and the charging losses at high rates are much less than lead acid also.
Overall, without continuing to yack about the technical aspects, it’s just a much better battery, takes up less space, weighs less, and has more power available.

There are likely decent arguments for other solutions, but the rest aside, this one won out because it was definitely more interesting.

Click past the break to read the rest of our interview with [wk057]!

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Solid State Tesla Coil Plays Music

If you’ve ever wanted to build a Tesla coil but found them to be prohibitively expensive and/or complicated, look no further! [Richard] has built a solid-state Tesla coil that has a minimum of parts and is relatively easy to build as well.

This Tesla coil is built around an air-core transformer that steps a low DC voltage up to a very high AC voltage. The core can be hand-wound or purchased as a unit. The drive circuit is where this Tesla coil built is set apart from the others. A Tesla coil generally makes use of a spark gap, but [Richard] is using the Power Pulse Modulator PWM-OCXi v2 which does the switching with transistors instead. The Tesla coil will function with one drive circuit but [Richard] notes that it is more stable with two.

The build doesn’t stop with the solid-state circuitry, though. [Richard] used an Arduino with software normally used to drive a speaker to get his Tesla coil to play music. Be sure to check out the video after the break. If you’re looking for a Tesla coil that is more Halloween-appropriate, you can take a look at this Tesla coil that shocks pumpkins!

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Tesla Model S Battery Teardown

Tesla Motors club user [wk057], a Tesla model S owner himself, wants to build an awesome solar storage system. He’s purchased a battery pack from a salvaged Tesla Model S, and is tearing it down. Thankfully he’s posting pictures for everyone to follow along at home. The closest thing we’ve seen to this was [Charles] tearing into a Ford Fusion battery. While the Ford battery is NiMH, the Tesla is a completely different animal. Comprised of over 7000 individual lithium-ion cells in 16 modules, the Tesla battery pack packs a punch. It’s rated capacity is 85kWh at 400VDC.

[wk057] found each cell connected by a thin wire to the module buses. These wires act as cell level fuses, contributing to the overall safety of the pack. He also found the water cooling loops were still charged with coolant, under a bit of pressure. [wk057] scanned and uploaded high res images of the Tesla battery management system PCBs (large image link). It is a bit difficult to read the individual part numbers due the conformal coating on the boards.

A second forum link shows images of [wk057] pulling the modules out of the pack. To do this he had to chip away the pack’s spine, which consisted of a 2/0 gauge wire potted in some sort of RTV rubber compound.

We’re sure Tesla doesn’t support hackers using their packs to power houses. Ironically this is exactly the sort of thing Elon Musk is working on over at Solar City.

Tesla Coil Auto-Winder

tesla winder

Tesla coils are awesome. But if you’ve ever built one, you know how tedious winding the secondary coil is. So [Krux] decided to build a machine to do it for him.

He’s currently working on his first Tesla coil — code-named Project Icarus — he doesn’t have all the logistics ironed out quite yet, but he’s been slowly collecting the components. What he does know is that he wants to use a 4.5″ secondary coil, using 22AWG magnet wire, meaning that’s a lot of turns! Since he’s also a member of a local hackerspace, he decided to make it a modular machine that can wind different sized coils for different sized projects.

Essentially, he’s built his own CNC lathe to accomplish this, well, missing one axis. There’s the main rotary axis, and a wire-guide that moves along it ensuring the coils are wrapped tightly without gaps. It’s an impressive build and you can tell he’s put a lot of thought into the design — He’s even got a semi-flexible 3D printed motor coupler on the wire-guide axis, to help mitigate quick acceleration! The main rotary axis is also driven by a 3D printed herringbone style gear — similar to the style used on Printrbot extruders. The rest of the build is made of plywood and pegboard — allowing for even larger coils to be wound by shuffling around the components. He’s even got a full featured command console with manual/automatic controls and an LCD giving feedback on the coil being wound!

Stick around after the break to see [Krux] explain the fascinating build, and to see a fun time-lapse of an 814-turn Tesla coil winding!

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“Professor Kill A. Volt” Shocks Pumpkins with his Tesla Coil

jj

[JJ Dasher] is back again this year, shocking some pumpkins! (Volume warning). We featured [JJ] two years ago for his Halloween candy shocking Tesla coil. He apparently has been busy in his mad scientist laboratory doing some upgrades. This year his coil is producing 5 foot long streaming arcs!

[JJ’s] Tesla coil is a uses two microwave oven transformers as a power supply. He also uses an Asynchronous Rotary Spark Gap (ASRG). As the name implies, a rotary spark gap uses a motor to turn a rotor. At certain points in the rotation, the rotor creates a small enough gap that a high voltage spark can jump across, energizing the primary coil. This idea is similar to an automotive ignition system distributor. [Pete] gives a great example of an ASRG in this video. Most ASRG based Tesla coils use the small motor to spin up the spark gap. Varying the speed of the motor creates the characteristic “motor revving” noise heard in the final arcs of the Tesla Coil.

[JJ] made things a bit more interesting by installing a couple of fluorescent bulbs inside a pumpkin near the coil. The coil lights them easily, and they glow even brighter when the pumpkin is struck. Still not satisfied, he also donned his grounded chainmail gloves and drew the arc to himself. We always love seeing people safely taking hits from massive Tesla coils, but this definitely falls under the “don’t try this at home” banner.

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Faceless child’s engineer father builds him a breathtaking ride

amazing-kids-car

Okay, the kid does have a face, but it looks like Dad blurred it for his protection. The real story here is the killer ride built by his engineer father. It’s far nicer than the cars driven by the Hackaday team, but then again, since it cost more than a BMW 3 series that’s no surprise.

[Lingzi] lives in China and does custom car work for a living. So to take on this project for his son was more of a stretch of the pocketbook than of his skill set. The car features a custom frame with rack and pinion steering, disc brakes, a rear differential, and a reputable suspension system. The body of the vehicle is crafted from carbon fiber. The lights all work and there’s an electric motor and transmission mounted just behind the driver’s seat. Unfortunately there’s no video of this in action (China blocks YouTube). But do take a look at the album above for pictures of the final paint job. There is also a little bit more information to be found in [Lingzi’s] Reddit discussion.

Tesla Model S handle dispenses beer; hides when done

tesla-model-s-beer-dispenser

Let’s face it, sometimes you need to take time out from engineering cutting-edge electric vehicles to over-engineer a beer fridge. And to tell you the truth, after seeing what [Matt Brown] managed to pull off we now have a gut-felt yearning for one of our own. He took a beer fridge and added a vanishing dispenser handle from a Tesla Model S.

You might be thinking that this an expensive part, and you’ve be more correct than you realize. It’s not even a stock part. This is a prototype that someone threw in the trash. [Matt] plucked it from oblivion and milled a spot for it in the door of the fridge. Your average [Joe] probably doesn’t know that the Model S comes with handles that pull themselves flush with the body of the vehicle.

[Matt] dug out insulation on the inside of the door until there was room to cut a hole for the handle. The clamped the assembly in place and used spray foam to re-insulate as well as glue it in place. An Arduino monitors the area below the tap. When you put your glass under the spout the handle extends. When you pull on it a solenoid drives the tap handle forward. This sounds pretty dry, but we think the demo after the break will have you lusting after one as well.

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