Simple extra battery for the expansion bay

So found the Expansion Bay Specs thread, had a question on it, around this Expansion Bay Developer Program - #9 by Aaron_Baff

Ideally you would want a hot swappable system that gets screwed in as normal and then you can yank the batteries out and shove in a new one. But given how much battery capacity you get with the regular battery, anyone who is going to complain about size is going to have to accept compromises. Small battery packs are going to degrade far more than larger packs, especially if there is no way to set charging and discharging capacity. On that note please do not touch pouch cells if you are going that route. They are compact, yes, but they always fail badly and damage components when they do.

You will get far more people wanting a large battery pack over a small one.

Rather than that, have it stick out at the bottom like this:

That way it can have more volume while still being transportable.
Many reviewers complained about the FL16 being less mobile with the GPU module attached.


I thought about potentially having a bottom tray underneath the laptop, but I don’t know if intake fans will allow it. Also, that can make it less transportable, which would be why a hot swappable expansion bay would be best.

I believe the fans mostly come in from the back and vent out the sides (or reverse?), rather than anything underneath. I could be wrong about that. Obviously that’d add to the thickness, but could add a LOT of battery. However, something to worry about is total Wh, since there’s an FAA limit of <100Wh before needing airline approval. Probably would be fine if it’s just a large battery pack on the bottom of the laptop, they probably wouldn’t even notice it even if it’s >100Wh.

The fans pull air in through the bottom and top (the opening above the keyboard) and exhaust out the sides (and with a GPU module the back, but since this battery would be instead of a GPU module that’s not relevant).

Just leave the intake area out. You’d have to do that either way, even if not expanding to the bottom.

Just have the expansion bay act as a connector for the hot-swappable batteries.
That way the expansion bay itself doesn’t have to be hot swappable; only the battery packs have to be. And as they are hot-swappable, just take them out before transportation, if necessary, and reattach them again upon use.

Working on version 2? 1.5?, I haven’t really shown the version 1 publicly. Anyway, I have been taking a bunch of the considerations you all have made and improving the original design. The calculated capacity for this one is 17.76 Wh. I’ll post a larger update soon.


Battery Pack Version 2


  • 17.76Wh battery
  • 66.5mm x 132mm x 9.7mm
  • LED battery indicator at the back
  • Housing and case are two separate pieces for ease of assembly and repair
  • less complex
  • thumb grip for ease of pulling in and out of slot


  • The back of the battery is not flush with the module
  • capacity is still limited and not within the legal flying limit**
  • shell is thin to accommodate the most capacity
  • The rear stock cover needs to be modified along with other parts of the original frame to fit correctly (will most likely need to be replaced with a 3D printed chassis)
  • tolerance issues with the frame rails
  • The battery pack can only fit one way due to the Z asymmetry of the rails
  • The cage is flimsy and warps out of the shell (I am guessing that the added PCB and cells will be enough to stiffen the frame)

**The FAA is unclear if two separate batteries carried by one device are considered one size.

Further development:

  • I need the physical expansion bay module on hand to test Z clearance with the laptop. I also need to check if replacing the stock frame with a modified one is possible.
  • Currently, the dimensions and circuits for the battery pack and the expansion module have yet to be specified. The most that has been discussed has been from @Aaron_Baff.
  • The battery cells used to get the Wh estimate are from here (Model No. LP703051). I’m considering having a custom pack made to increase capacity further.
  • I’ve been looking at the USB PD standard to see if the theoretical 14.8v the pack can supply will be adequate for the 45w spec.
  • Looking at routes for development and ways of distributing products of this type. Thus far, the plan is to keep everything open source (it makes no sense to do anything else). 3D printing the cage, along with a list of parts for assembly and instruction, seems the way I’m going to go with it. Along with having assembly kits and/or complete units available. Currently, the battery shell and cage are hard to print; I’m going to work on optimizing the design for printing once a final design has been reached.

I would love to hear feedback (criticisms, improvements, thoughts, ideas, etc.)

Some more photos of version 2
note: the USB C plug is not designed yet but does fit within the current dimensions


For the FAA limit…just pull it out and carry it separately. Fixed. They’re fine with multiple <100Wh batteries that are carried/stored reasonably.

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This is awesome!
I probably won’t be using this as I’ll be running the dGPU, but I love that you’re putting in the work for us :​)

Regarding distribution: Wouldn’t it possible to use the framework marketplace for that, if the result is good?

I also plan to use the dGPU, so I won’t be using my own product. But I plan to create a hideaway second monitor that clips onto the screen. I could technically make a similar design for a clip-on battery module that mounts on the display frame, mainly for people who use the dGPU on the go and need the extra capacity. But that’s if it seems reasonable to develop.

I do plan to do this, but it’s too far down the road to promise that’s the case.