Lucy

20kW mobile power solution for renegade raves.

This is the most recent project that @faited and I have been working on. The idea is to package two reclaimed Tesla Model S battery packs (5.3kWh, 74p6s 18650 Li-Ion each) in a wooden box with BMS to build a modular power solution.

Aug 24, 2023 at 1:02pmWeb
Show threadLucyAug 24, 2023
The batteries are design for easy assembly and mechanical protection. Fait did the CAD for these gorgeous CNC machines wooden boxes that slide in two packs. Besides that, each box has its own BMS from AliExpress, along with a 160A circuit breaker and active ventilation.
Show threadLucyAug 24, 2023
Originally we only planned to build the batteries ourselves, and get a 5kW inverter from amazon. During a load test however we noticed that the inverter would overload from peak loads when the bass drops, and I decided to spec out a custom inverter design.
Show threadLucyAug 24, 2023
The issue with off-the-shelf inverters is that the power electronics is designed for high constant load, and the limiting factor with traditional applications is cooling.
In our application however, we have low constant load, but all power electronics must be speced for 10x burst loads.
Show threadLucyAug 24, 2023

However all inverters that have such beefy IGBT modules are giant and heavy. Also we wanted something that fits in our existing 19" amp rack. I therefore decided to build our own inverter inside a used 4U server chassis.

I 3D printed a mount for a 5" LCD connected to a rPi running grafana.

Show threadLucyAug 24, 2023
I still had connections to Chinese EV charger manufacturers, and it was easy to locate the right building blocks for this project. At it's core, the inverter consists of two 8kW 48V -> 400V LLC boost converters, a 22kW SPWM IGBT inverter and a embedded linux system for monitoring and protection.
Show threadLucyAug 24, 2023

With a single LLC, all batteries must be connected in parallel before the rave, and this requires them to have the same voltage.

The idea behind two parallel LLC converters is that you can hotswap batteries with different SOC without turning off power at any time. It also adds redundancy.

Show threadLucyAug 24, 2023
And here is the setup in action, two batteries powering our two 2x 15” paraflex sub + synergy horns 10kW soundsystem for 8h straight without any noise or smell from nasty gasoline generators.
Show threadLucyAug 24, 2023
And this is where the bass is stored.
Looking forward to more amazing DJs stress testing this design, especially at our Hardcore / Terror event in November~
Show threadNyx PhoenixAug 24, 2023
@lucy i hope you have resistors to discharge those,, 🦋
Show threadmav Aug 24, 2023

@lucy this is absolutely bananapants crazytown, and I mean that in the best possible way. Hacker ethos at its finest

Bravo!

Show threadpenguin42Aug 24, 2023
@lucy What is that very very scary looking Toroidal device on the left?
Show threadLucyAug 24, 2023
@penguin42 it’s the main output inductor for the sine wave inverter. This inductor filters the high-frequency PWM to create a pure sine wave output.
Show threadGraham Sutherland / PolynomialAug 24, 2023
@lucy that's a beast of a build. I'm a sucker for hardcore power electronics stuff.
Show threadStephen K 🔑☢️⚛️🇺🇦 Aug 24, 2023

@lucy Holy crap, I am beyond jealous of that.

Way better than my repurposed Dell 3Kw UPS setups with battery extenders.

Show threadjasegAug 24, 2023
@lucy Wow, thay's a lot of power electronics inside a very compact package. I wonder at what point it starts making sense to drive the speakers straight from the battery bus through some sort of class D setup.
Show threadJasperAug 24, 2023
@lucy how do you charge the batteries? Just a beefy DC PSU and the BMS handles balancing and current management?
Show threadLucyAug 24, 2023
@jasper Yea that's exactly what we are currently doing.
Show threadKevin Karhan Aug 24, 2023

@lucy @faited I'd not choosen wood but rather Sheets of Acrylic and Metal as a strong yet non-conductive case material that doesn't add flammability...

But that's just me being picky in terms of safety...

Show threadLucyAug 24, 2023

@kkarhan @faited Our tool shop is well set up to work with wood, and Fait has plenty experience with building strong enclosures from wood for speaker cabinets.

Flammability is no big concern; if the packs enter thermal runaway no acrylic sheet will save you. Best you can do is tough protection from mechanical damage, and for this wood is a good choice (flight cases for stage amplifiers etc are still build from wood to this day).

Show thread0xC01DC0FFEEAug 24, 2023
@lucy damn, that is cool. Also slightly terrifying.
Show threadJulie moved to @[email protected]Aug 24, 2023
@lucy @faited I thought I was reading this in my #HamRadio column and I was *very* concerned to read "20kW"
Show threadAbby ☃Aug 24, 2023
@lucy @faited Whoa, I didn't realize you could buy reclaimed Tesla packs. I've been looking for a solution for an off-grid cabin, and 5KWH for $1000 is a steal.