Surge, et ambula. — John 5:8 (Vulgate)
A single-use emergency phone charger built around a lithium thionyl chloride primary cell. Designed to sit in a vehicle for 5 years untouched, survive Florida heat, and deliver ~30 minutes of phone charging when activated by pulling a tab. After use, it's discarded and replaced.
This is a hardware project: 3D-printed SLA enclosure, off-the-shelf components, no firmware to speak of.
A standard USB power bank with lithium-ion cells self-discharges to nothing inside a year. Stored in a 70°C glovebox it ages even faster — and modern cells with built-in protection circuits often refuse to wake up after deep discharge. By the time you need one, it's a brick.
Lithium thionyl chloride (Li-SOCl₂) primary cells solve this. They have <1% self-discharge per year, a 10+ year shelf life, and an operating range of -60°C to +85°C. They're already used in things that have to sit dormant for years and then just work: water meters, military equipment, medical implants, pipeline sensors.
Lazarus is the same idea, packaged as a roadside emergency device.
| Property | Value |
|---|---|
| Cell | 1× Saft LSH14 (or equivalent C-cell Li-SOCl₂) |
| Energy delivered | ~14 Wh @ 5V USB-C |
| Output | USB-C, 5V @ 1.5A (7.5W) via CH224K PD trigger |
| Charge time | ~30 minutes, enough for emergency calls/maps |
| Shelf life | 5 years (rated 10+, derated for hot-car storage) |
| Temp range | -40°C to +70°C operational, +85°C max storage |
| Form factor | 33mm × 98mm cylinder + caps, ~115mm total length |
| Weight | ~80g assembled |
| Activation | Irreversible pull-tab |
| Reusable | No — single-use, replace every 5 years |
- Read docs/DESIGN.md to understand the circuit.
- Order parts from docs/BOM.md.
- Print enclosure parts from hardware/enclosure/ — see hardware/enclosure/print_settings.md.
- Print the thread fit test first. Dial in clearance before committing to a full body print.
- Follow docs/ASSEMBLY.md for the build sequence.
- Write the manufacture date on the side label. Drop it in the glovebox.
- Set a calendar reminder for 5 years out.
Read SECURITY.md before doing anything with Li-SOCl₂ cells. Short version: do not short, do not solder bare cells, do not puncture, do not incinerate, do not check on an airline as bulk cells. They are safe when used correctly and dangerous when not.
| Phase | State |
|---|---|
| Concept | ✅ Complete |
| BOM finalized | 🔄 In progress |
| Enclosure v2 | ✅ SCAD source committed |
| Thread fit test | ⏳ Pending first print |
| Circuit bench-build | ⏳ Pending parts |
| First full assembly | ⏳ Pending |
| 5-year field test | ⏳ 2031 |
- Code (SCAD source, Python tools): MIT — see LICENSE
- Hardware design (enclosure, schematic, PCB if any): CERN-OHL-P v2 — see LICENSE-HARDWARE
- Documentation: CC-BY-SA 4.0
Use it, fork it, build one. If you improve it, send a PR.