A demo “gravity battery”: you hoist a weight to store potential energy, then let it descend through a speed-controlled winch that turns a generator to make 12 V / 5 V DC for lights, USB, or a small fan. It’s safe, visual, and perfect for teaching m·g·h, gearing, rectification, DC-DC control, and braking.

Parts Used:

1. Mass & lift path: Sandbags/barbell plates 25–100 kg, rope (rated ≥ 10× load MBL), top pulley, guide rails or a clear shaft.
2. Winch module: Steel drum (Ø 80–120 mm), worm or planetary gear (self-locking is good), one-way clutch/ratchet, shaft bearings.
3. Generator: 3-phase BLDC / PM DC motor (200–500 W rating; used as generator).
4. Power electronics:
5. 3-phase bridge rectifier (≥35 A, 100 V) + bulk capacitor (2 200–4 700 µF, 63 V).
6. Buck DC–DC to 12 V bus (10–20 A) + USB 5 V module.
7. Programmable electronic load or current-controlled buck to regulate generator torque → constant descent.
8. Supercapacitor (10–30 F) to absorb pulses; fuse & TVS.
9. Controls & safety: E-stop, normally-on brake (spring caliper or electromagnetic), centrifugal overspeed brake (fail-safe), top/bottom limit switches, enclosure/guards, load cell or in-line scale (optional).