Lumen – Eternal Flashlight That Doesn’t Need Batteries

  • Lumen - Eternal Flashlight That Doesn't Need Batteries

Have you ever thought how much energy is wasted by humanity? Exactly, right now by You!

I’m absolutely sure that if we want to build a better world and leave next generations thriving earth we need to find alternatives to energy sources that pollute nature.

It’s easy to say: GO GREEN, a bit harder to THINK GREEN. Now I propose you to BE GREEN.

Let me introduce Lumen – flashlight that doesn’t need any external energy source except your warm touch 😉

Heat-activated light
Heat-activated light


It is an ordinary flashlight with brightness comparable to your smartphone’s except his main feature – it doesn’t need batteries and virtually eternal.


Lumen has relatively simple work principle – you touch TEG (Thermoelectric Generator) – small ceramic bar that can produce electric current when we provide temperature difference between upper and lower parts of TEG.

In my application difference between temperature of your body (about 98 °F) and environment (at least 82 °F) is enough to generate power for single led. Metal body of Lumen serve as a radiator.

To better understand the main principle look at diagram:

Courtesy of Power Practical
Courtesy of Power Practical


As you understand, we can’t power really high-output led just with touching small TEG.

However, when your temperature is 98 °F and air temperature is 82 °F Lumen produce about 15 mA@3v. When difference is bigger – excessive power is stored in a capacitor to power Lumen whenever you need it. Such amount of energy is enough to power 5 mm Cree led with 3000 mCd light output.

Lumen in action
Lumen in action


  • Weight : ~ 35 gramms \ 1,2 oz for Aluminium version
  • Weight : ~ 45 gramms \ 1,5 oz for Titanium version
  • Dimensions: 40 mm x 10mm x 80 mm \ 1,6″ x 0,4″ x 3,2″
  • 5mm ultrabright CREE led
  • Light output: 3000 mCd


Before you can use flashlight you need to find it! (Yep, I’m a fan of Captain Obvious)

How to help you to find it in a complete darkness? You can order Lumen with tritium vial – glass tube with a phosphor layer in them and tritium gas inside the tube. This tiny vial will produce light for over a decade. Just look at photo:

Lumen with tritium mark in a dark room
Lumen with tritium mark in a dark room
Tritium vials in a complete darkness
Tritium vials in a complete darkness


Lumen is available in 2 body materials: Titanium and Aluminium. Both are available with or without Tritium tubes.

4 types of Lumen
4 types of Lumen


Before I launched Kickstarter campaign I’ve created numerous prototypes to achieve maximum efficiency

Early prototype
Early prototype
Lumen internal parts outside the case
Lumen internal parts outside the case


According to my plan I should start shipping Lument to bakers in a 3 month after the end of KS campaign.

P.S. This tiny flashlight is only a first step in my research of green energy sources. If you care about this – please support me. Can’t do this via pledge? I’ll be very grateful if you spread the word through the web: facebook, blogs, twitter, instagram – every repost make me closer to achieve my goal and all of us to a better place to live on.

Where to buy
Lumen - Eternal Flashlight That Doesn't Need Batteries

Touch Lumen and heat of your body will be converted to Light! Everlasting light source that is always with you.


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