Posted by CANbike on Sat, 3 Jan 2015

9 Volt Battery (6LR61) Flashlight / Lantern

A 9v flashlight / lantern can be made cheaply and easily. The essential components are:

  • a 9 volt battery (6LR61)
  • a resistor (300+ Ohm) wired before the LED anode (+)
  • a LED

Excluding the battery the following flashlight and lantern were made for less than $2 each.

9-Volt Battery (6LR61) Flashlights-01

Why 9 Volts?

First, low lumen / long runtimes can be achieved with a single 9V battery (6LR61) and a resistor. For example, using a 1K Ohm resister results in a current draw of ~6 mA for 100+ hours.

Second, it is much simpler to create a voltage drop across a resistor, than it is to use a step-up converter for 1.5V batteries.

Third, in long blackout scenarios, 9V batteries are easy to find in-stores and around the house. Retailers will still carry them even though AA and D cells may be sold out. In the house, they can be found in smoke detectors, garage door remotes, multimeter, etc.

Fourth, used 9V batteries may have plenty of power left. Though they may seem dead in other electronic devices, there’s still plenty of energy left for many hours of light with a LED. Don’t let those batteries go to waste (with proper disposal) until it’s truly empty.

Prototype 9V Flashlight From 3AA Case

  • A 3xAA enclosed case with built-in switch ($0.88) was used to make this flashlight.
    9-Volt Battery (6LR61) Flashlights-02
  • Rubberized protection is cut from an old bicycle inner tube
    9-Volt Battery (6LR61) Flashlights-03
  • The innards of the flashlight
    9-Volt Battery (6LR61) Flashlights-04
    • Metal tabs for AA batteries were removed with pliers
    • One plastic tab was cut out to make room for a 9V battery
    • A chisel was used to create more room for the battery
    • Black wire (-) from battery clip was soldered to switch
    • Hole drilled for red wire (+)
    • Hole drilled for LED
    • Wire screw connectors were used for easy swapping of resistors and LEDs
      • For increased strength or permanent use, wires should be soldered instead

Rugged Water Resistant 9V Lantern

  • This mini-lantern, made from a black film canister, was designed for emergency use
    9-Volt Battery (6LR61) Flashlights-05
  • The battery clip, LED and resistor were installed onto the canister cap
    9-Volt Battery (6LR61) Flashlights-06
    • The LED and resistor were soldered on top of the battery clip
    • Components were then covered in hot glued for insulation and water resistance
      • Hot glue ended up being an ugly glob of a mess . . . DOH!
    • Hot glue was then covered with electrical tape for a neater appearance and increased insulation
  • Bottom of the canister cap revealing the battery clip connectors
    9-Volt Battery (6LR61) Flashlights-07
  • Film canister is the right size for a 9V (6LR61) battery
    9-Volt Battery (6LR61) Flashlights-08
  • Canister is covered with an old bicycle inner tube, and electrical tape on the bottom
    9-Volt Battery (6LR61) Flashlights-09
  • Cap snaps onto the 9V battery to activate the LED
    9-Volt Battery (6LR61) Flashlights-10
  • Snap the cap and battery onto the canister for ruggedness and water resistance
    9-Volt Battery (6LR61) Flashlights-11
  • 9V Mini-Lantern fully submerged in a bowl of water and still running
    9-Volt Battery (6LR61) Flashlights-12
  • Invert the battery for safe storage
    9-Volt Battery (6LR61) Flashlights-13
    • There’s storage room to include other small items
      • WARNING: DO NOT include metal items as they may short out the top of the battery and cause a fire

Related Item(s): Review

Related Item(s): Articles

Related Item(s): Resource