Batteries die, chargers get lost and apps stop being supported. I like things that just keep working. These are radios, phones, lights, watches and instruments that need no battery at all. Each guide covers what to buy, why it's the right choice, and how to build or set it up.
Every guide follows the same pattern: what to expect, why this way is best, how it works with a diagram, what to buy with a reason for each part, then the steps.
I'm honest about limits. A crystal radio is quiet. Most "wind-up" radios hide a battery. Where something hasn't been built or tested yet, the guide says so.
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A radio powered only by the signal it catches. Medium wave and shortwave to about 18 MHz, one band knob.
Read the guide →The wartime radio made from a razor blade and a pencil lead. A rough detector, a brilliant first build.
Read the guide →Two handsets and a long wire. Your voice is the power. The same idea navies still use.
Read the guide →Learn it by ear, send it with a mirror, and practise on a hand-cranked light set.
Read the guide →Electricity from two metals and some soil. How much you really get, and how to light an LED with it.
Read the guide →Most of them hide a battery that wears out. How to spot it, and which ones really need none.
Read the guide →Lights that work as long as you pedal. Hub or bottle dynamo, which lamps, and how to wire them.
Read the guide →An engine that runs on a mug of hot water. No fuel, no battery, and you can watch every part move.
Read the guide →Wound by hand or by your wrist. How they work, four good picks, and how to look after one.
Read the guide →Maths with no power. How a slide rule multiplies, which to buy, and practice to get quick.
Read the guide →Instruments that read the world with no battery, and how to take a bearing or tell solar time.
Read the guide →Forecast the weather from air pressure. What the needle means, and which weather glasses are just decoration.
Read the guide →