Vintage Military Flashlight Upgrade

I don't like having unused things in my house!

About 20 years ago my father bought this old military flashlight. We used it for a few years until the battery ran out.

The torch worked with non-rechargeable batteries and the light emitted wasn't much... It has been unused for many years but I think it still works.

To give it a new life, it's time to update it, with LEDs and rechargeable lithium batteries.

The purpose of this guide is to improve and update the flashlight, without modifying the original structure, in order not to ruin this vintage object.

Components

• Step-Up Voltage Regulator module
• TP4056 module (only the "micro" version fits well)
• 18650 Battery (don't buy batteries... reuse them from old devices)
• 6mm Nickel strip
• 1w white Led
• 8mm Led
• reistors
• m3 screws

Tools

• 3d printer
• hot glue gun
• soldering iron
• super glue

The main idea is to make a new battery and a new bulb that can be easily replaced with the originals.

The most complicated work was to redesign everything with Fusion 360, inserting all the spaces and joints to place the new electronic components inside.

Of course I made the designed objects by 3D printing.

The result of this process was satisfactory and I managed to create functional objects that can be used in everyday life. As often happens to me, I came up with other changes to make assembly easier and more reliable, so later I'll update you on the improvements to the project!

https://www.thingiverse.com/thing:5926816

The flashlight uses an old 4.5v battery. I believe the model is "3LR12".

These types of batteries are heavy and bulky and I don't think there are any rechargeable models.

I have many old 18650 lithium batteries in my lab that seemed perfect for the project.

Unfortunately the 18650s are too long to place them vertically in the space of the original battery, so I placed it at an angle, conserving space for the charger module and step up regulator.

The top cap has a hole that I filled with transparent hot glue, to be able to see the tp4056 module leds that indicate the battery charge status.

To build the battery contacts I used pieces of nickel strip.

The internal circuit is very simple, just be careful to calculate the length of the cables well, to make assembly easier. The step up regulator is adjustable via a variable resistor and I adjusted it with an output of 4.5v to give the battery the original voltage so that it can also be used with other devices.

To update the bulbs I created a 3d model of the small "e10" bulb thread. Of course, the inside of the model is hollow to pass the contacts. The upper part of the bulb is designed to fit the LEDs easily.

I used 2 types of LEDs I had at home, an 8mm LED which I fed at 100mA with a 10 Ohm resistor and a 1W power LED which I fed at 200mA with a 5 Ohm resistor.

At the end of this work, I think I've improved an old and obsolete object, adding modern features, like a good luminous efficiency and the possibility of recharging the batteries.

I think I will soon add updates to this guide to improve the electronics, the 3D design and make this idea more exportable to other devices.

Please leave me your impressions with a comment and report technical and grammatical errors!

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