Top Stories· August 18, 2026 at 08:11 p.m.
Reviving Dead Batteries with Joule Thief Circuits
Key takeaways
- A joule thief circuit can be built using a transformer and a transistor
- The circuit can extract residual energy from dead batteries
- A single 1.5-volt battery can power a 3-volt LED with a joule thief
A physics professor demonstrates a simple electrical circuit, known as a 'joule thief', that can extract residual energy from dead batteries to power devices longer. The circuit pairs a transformer and a transistor to induce a higher voltage in the secondary circuit, enabling a single 1.5-volt battery to light an LED requiring 3 volts.
