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bac-hardware/eps/battery-contact/battery-contact-pcb-18650-2s2p
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Manuel Imboden abab291bae Fix image URL
2026-05-12 19:19:42 +02:00
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Release EPS Battery Contact PCB 18650 2S2P v2r1
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Release EPS Battery Contact PCB 18650 2S2P v2r1
2026-05-07 14:29:40 +02:00
README.md
Fix image URL
2026-05-12 19:19:42 +02:00

README.md

EPS Battery Contact PCB 18650 2S2P

Subsystem: EPS Status: 🧪 Sample boards ordered for testing

Design Files:

Manufacturing Files:

  • Version: v2r1

  • KiCad: v10

  • Date: 2026-05-07

  • Release: eps-battery-contact-18650-2s2p-v2r1

  • Artifacts:

    • Schematics: Included (PDF)
    • Gerbers, Drill and Centroid: Included (ZIP)
    • BOM: Included (CSV)
    • Panel File: Included
    • Instruction:
      • Ordering: Included (PCBWay: TXT, separate files for snap-apart and 1×4 panel variants)
      • Sourcing: Included (DigiKey: URL; Snaptron: URL)
      • Assembly: Not Included (hand assembly — see Notes)
    • 3D Model: Included (STEP)
    • 3D Render: Included (WebP)

    3D Render

Overview

The EPS Battery Contact PCB sits below the EPS main board and provides contact domes for the terminals of four 18650 cells. The board is held in place by the cells themselves and by the EPS bay inserts, which fit snugly around the cells and the contact PCBs and have pockets that allow the contact PCB to reach up to the EPS main board, where 4 pins per side interface with corresponding receptacles on the main board.

Two contact PCBs are required per battery pack — one on the Ym side and one on the Yp side. The same mechanical concept supports 4P, 4S, and 2S2P configurations: the pack topology is set entirely by the contact PCB pair. This v2r1 is the 2S2P variant.

Specifications

  • Dimensions: 36.4 mm × 68.7 mm (snap-apart Ym + Yp pair as manufactured)
  • Thickness: 1.6 mm
  • Layer Count: 2
  • Copper Weight: 1 oz
  • Stackup: PCBWay standard 2L
    1. F.Cu — Power
    2. B.Cu — Power
  • Impedance Targets: Not controlled
  • Panelization: Released in two variants — single snap-apart (Ym+Yp manufactured as one, separated with a C-cut or by manual scoring) and 1×4 panel (4 snap-apart pairs = 8 individual PCBs after separation)
  • Mounting: Held in place by 18650 cells and EPS bay inserts; no fasteners
  • ECAD: Schematic and layout created in KiCad 9.0.8 and migrated to KiCad 10 for release

Connectors and Interfaces

  • Contact domes: Snaptron FB07 (4 per PCB). Not stocked at DigiKey — order samples or bulk from Snaptron directly.
  • Vertical interconnect pins: Mill-Max 3320-0-00-15-00-00-03-0 (up to 4 per PCB as 2× 2-pin groups). Hand-soldered coplanar with the PCB; mate with the EPS main board above.
  • Cell balancing footprint: 0603 DNP resistor footprint (populate with 100R for passive balancing) and a 5 mm wide central area reserved for future active balancing components. Aligns with the corresponding pocket in EPS Bay Insert v4.

Configuration Notes

  • 2S2P variant (this revision): Only the Yp-side PCB has its Mill-Max pins populated. The Ym-side pins are not required, so each pack uses 4 Mill-Max pins total (not 8).
  • Eventual 4P and 4S variants: Use the corresponding contact PCB revision; pin population may differ.

Panelization

KiKit configuration for panelizing battery contact boards:

Known Limitations & Design Decisions

  • Hand assembly required: Mill-Max pins must be placed and soldered manually, coplanar with the PCB. Tedious but proven to work.
  • No active balancing in this revision: Only a DNP 0603 footprint for passive balancing (100R) is included, plus a 5 mm central reserved area for a future active balancing implementation.
  • Snaptron-only sourcing for contact domes: Snaptron FB07 is not available from DigiKey.
  • Centroid file does not include pins: The centroid file lists contact dome positions only. Mill-Max pins are hand-placed and are not on the centroid.

Revision History

Version Date Summary
v2r1 2026-05-07 New contact pair spacing fits a 2.54 mm grid; passive balancing changed from solder jumper to DNP 0603 resistor footprint (100R); 5 mm central area reserved for active balancing (matches EPS Bay Insert v4 pocket)
v1r2 2025-03-19 Introduced 1×4 panel variant; added passive balancing solder jumper
v1r1 2024 Initial release

Notes

  • Sample boards have been ordered for testing.
  • The board is intended for hand assembly only: contact domes can be reflowed using the centroid file, but the Mill-Max pins are placed and soldered manually.
  • This board is not flight-qualified.
  • Recommended cell type: LG MJ1.

License

CERN OHL-S 2.0

Contributing

Contributions to the Build a CubeSat hardware ecosystem are highly appreciated! To keep things structured, here's how you can contribute:

Fixes & Improvements to Existing Designs

  1. Create a new feature branch (git checkout -b feature/your-feature-name)
  2. Commit your changes (git commit -m 'Brief description of change')
  3. Push to the branch (git push origin feature/your-feature-name)
  4. Submit a Pull Request (PR) with a clear description of the changes

New Designs & Community Contributions

  • Create your own repository
  • Share a link in community discussions or open an issue
  • If relevant, it will be referenced in the docs 🙌

Supporting This Project

If you'd like to support the Build a CubeSat project further, consider these options: