Open source Lego Technic battery box - LBX

[legomen]

Hi Eurobrickers,

Recently I have decided to develop a new battery box with controller for Lego Technic stuff. An idea emerged when I was developing brushless L Motor with integrated ESC, i.e. LMX (Lego Motor eXtreme)

This motor demands more powerful power supply then ordinary Lego battery can provide. There are of course alternatives to Lego battery (e.g. Buwizz), but this motor can have even higher peak current than those batteries are comfortable with.

So I have decided to set some basic requirements for the new battery system:

1. Replacable LiION cells. One can swap batteries in the field with new charged ones when needed. Look, a whole day of playing with Lego:). For storage, just remove the batteries and no worries.

2. 2S battery topology. Peak 8.4V, because most brushless motors of this size are specified for this voltage. 

3. 2xPF connector and 2xPU connector. 2 LMX motors and 2 PU motors, acting as servo or not.

4. Full BMS and Charger integrated.

5. Open Source Firmware - direct connection to standard game consoles or phone (acting as console).

6. No, and I mean NO Android or Iphone app. Those apps need to be regulary updated and who has time to do it;)

7. Low price - of course.

 

I came up with preliminary design and look for the new battery and I would like to discuss pros and cons. 

This is my first iteration of mechanics. Some details are still missing. I have deliberately omit battery cell cover in favour of easier replacing of batteries in the model. And it looks cool IMHO, especially with some fancy cells:) I chose the LiION cells instead of pouch LiPo due to high current demand and obtainability. Also 18650 format is somehow standard and you can buy those cells almost everywhere.

Battery pack is 10x5x4 studs, a little bigger then Buwizz, but it has more then twice of energy (with 3000mAh cells 25Wh).

Have fun.

 

[Toastie]

Hi @legomen,

wow, this is a really educated approach! All things integrated that are >relevant< - as it tackles nearly all the "issues", which came up over the recent years if not decades.

But this is more a >powerful PF/PU controller< than (just) a battery box!

Open source = best firmware/software development possible.

Everything else: Totally cool!

All the best
Thorsten   

[Wapata]

10 hours ago, legomen said:

. I have deliberately omit battery cell cover in favour of easier replacing of batteries

I wonder if puting only batteries connectors (power and the other) can be a great idea for a variant product... Or if people will put way to big batteries 

 

It's a great design you have made here !! Is it a USB C port in the side ? 

[legomen]

Just now, Wapata said:

I wonder if puting only batteries connectors (power and the other) can be a great idea for a variant product... Or if people will put way to big batteries 

I do not understand what you mean with that.

 

1 minute ago, Wapata said:

It's a great design you have made here !! Is it a USB C port in the side ? 

No, it is an USB Micro. This is due to a fact that I am planning to use RPi Pico W for the main controller board. Why Pico? It is cheap and available. It has a good roadmap. I would also prefer USB-C. Maybe in the future:)

[Wapata]

Big batteries pack have a power output and an output to check each cell individually (I'm not finding the English word right now) so instead of have a cell holder, one can put a very big battery pack.

[legomen]

Just now, Wapata said:

Big batteries pack have a power output and an output to check each cell individually (I'm not finding the English word right now) so instead of have a cell holder, one can put a very big battery pack.

Ok, I understand now. You mean a LiPo pack connector, like one used in RC world. Well, it is an option, but I think somehow against my principles to not use stuff from RC world in Lego Technic. If the battery would be encapsulated in the casing (like Buwizz), maybe. On the other hand, 18650 batteries are way easier to use, they are powerful (if proper type is used) and easily replacable.

[Wapata]

Okay, it was just an idea floating around 

10 hours ago, legomen said:

NO Android or Iphone app

I hope you will make others devices like this one to control more outputs of on or the other type of connector. I'm soooooo disappointed by the lego compatibles apps. 

How can an output can be attributed to one or an other input of a gamepad controller by the way ? Do multiple devices can be connected to a single gamepad ? Are we only talking about the last Playstation and Xbox pads or there is a list somewhere (... I ... I Have wiimote with nunchuk  )

[legomen]

3 minutes ago, Wapata said:

How can an output can be attributed to one or an other input of a gamepad controller by the way ?

Good question. There are numerous ways to do it. Firmware can have a special button on a gamepad dedicated to enter programming mode. Or a simple tty console on an USB port for programming.

 

5 minutes ago, Wapata said:

Do multiple devices can be connected to a single gamepad ?

Anothe great one. I was thinking of that also. The easiest way would be to have one device as a slave to another. Master will be connected to the gamepad and channeling commands to the slave.

 

7 minutes ago, Wapata said:

Are we only talking about the last Playstation and Xbox pads or there is a list somewhere (... I ... I Have wiimote with nunchuk  )

Firmware would be supporting not just Playstation or XBox, but also other devices, if those are supporting universal Joystick protocols. There are some devices with proprietary protocols and those would need to be supported through firmware change. This way open source:)

IMHO, mixing RC world and Lego Tecnic is like putting Marvel superheroes and Disney characters in the same movie Wonder what would happened? 

[2GodBDGlory]

Ooh, I think there's some smart design choices here! I love the usage of 18650 cells! More pinholes would be great, but if there's not the internal space for them, it's not worth making it larger to incorporate them.

Will the firmware have support for at least basic servo modes for PU motors?

I'm looking forward to seeing progress on this!