Modification of a flashlight (from AAA batteries to 18650 battery)

Selecting and purchasing a flashlight is a difficult and tedious task. At least for me. I approach this matter with all meticulousness and responsibility. It is necessary to take into account all the advantages and disadvantages of the product. Type and capacity of batteries, parameters, weight, degree of water resistance and much more. So that he does not fail at the most inopportune moment. I wanted to buy a small pocket flashlight, waterproof, powered by a single 18650 battery. However, I could not find the desired product in local stores. I was already thinking about ordering from an online store and, after waiting 2-4 weeks, getting what I needed... But suddenly I came across something that almost suited me. Almost. The flashlight had the dimensions I needed and all the necessary qualities, but there was one “but” - it worked on three AAA batteries (pinky).
Modification of a flashlight from AAA batteries to 18650 battery

Modification of a flashlight from AAA batteries to 18650 battery

Having a special container with four constantly charged 18650 batteries in my backpack, I absolutely do not want to use other batteries. Moreover, such small and not capacious ones as little ones.But there is always a way out! Having examined this flashlight in the store, a modification scheme immediately emerged, and without thinking twice, I purchased it with the goal of remaking it in my own way in the near future.

Will need


  • A burr machine with a cutting disc (or an emery machine).
  • Soldering iron, tin and flux.
  • Plastic tube (for housing insert).
  • Aluminum self-adhesive foil.
  • Scissors.
  • Stationery knife.
  • File.
  • Sandpaper (or sanding cloth).
  • Secondary glue.

Flashlight conversion


The main problem is that the flashlight’s “native” power supply (the housing in which three AAA batteries are located) is slightly wider, and one and a half centimeters lower than the 18650 battery.
Modification of a flashlight from AAA batteries to 18650 battery

This means that the body of the flashlight itself will be too small in height for 18650. In terms of voltage, 18650 is almost identical to three little finger batteries, 18650 produces 3.7 volts, and three little finger batteries give a total of 3.6 volts (1.2 × 3 = 3.6) . This means that if the body is too small, you need to lengthen it. It was quite problematic to find a suitable insert tube that would fill the extra space between the battery and the walls of the flashlight. In the end, I was never able to get a suitable insert... I simply took a more or less suitable tube that included 18650 and, installing it on a drill, removed the excess thickness from the rotating workpiece from the outside with coarse sandpaper! So, let's disassemble the flashlight. Unscrew the front and back parts of the flashlight from the middle one and set it aside. Using a burr with a cutting disc, we cut the middle part of the flashlight body into two equal halves.
Modification of a flashlight from AAA batteries to 18650 battery

We sand the sawn edges with sandpaper so that they become even and smooth.
Modification of a flashlight from AAA batteries to 18650 battery

Next, we insert the liner tube into the front part of the flashlight with a reflector screwed onto it, and put the back part on top with the bottom and button screwed onto it. The result is a new, elongated body that fits the width of 18650.
Modification of a flashlight from AAA batteries to 18650 battery

Modification of a flashlight from AAA batteries to 18650 battery

Now let's adjust the height, insert the battery into the case, measure out the excess on top, take out the liner and cut off the measured edge with a utility knife.
Modification of a flashlight from AAA batteries to 18650 battery

Modification of a flashlight from AAA batteries to 18650 battery

Modification of a flashlight from AAA batteries to 18650 battery

Also in the design of the flashlight, inside the body, there are two metal rings and a metal strip that connect the plus and minus on the switch button. Naturally, after lengthening the body, the metal strip became too short for the new design. We also had to adjust the rings to fit the liner tube.
Modification of a flashlight from AAA batteries to 18650 battery

The layer of soft plastic was quite easily and quickly removed with a file from the edges of the liner, where the ring should sit.
Modification of a flashlight from AAA batteries to 18650 battery

Modification of a flashlight from AAA batteries to 18650 battery

The second, front ring, was inserted inside the front of the flashlight, where the reflector, lens and Light-emitting diode, so I didn’t have to mess with it. Let's do it simpler with the metal strip connecting the rings; Simply stick a strip of self-adhesive aluminum foil onto the liner.
Modification of a flashlight from AAA batteries to 18650 battery

We put the back ring on the prepared back part of the liner.
Modification of a flashlight from AAA batteries to 18650 battery

Now let's work on the “head” of the flashlight. On the former power supply, with pinky batteries, there was a small bulge on the positive contact that was in contact with the positive. On the 18650 battery, both contacts are flat, so I had to solder the same spring to the positive contact of the front part of the flashlight as is on the negative, rear part.
Modification of a flashlight from AAA batteries to 18650 battery

Modification of a flashlight from AAA batteries to 18650 battery

Now let's put the new body together.
Modification of a flashlight from AAA batteries to 18650 battery

All the details fell into place like family! All that remains is to drip super glue into the joints between the liner and the sawn edges of the body to restore the tightness.There is still space left, or rather, it turned out to be a groove that was formed after installing the sawn ends of the old case on the liner. This is an individual matter for everyone; Before gluing all the parts, you can fit a piece of tube with suitable parameters to this place. I decided to just wrap a little tape and black insulating tape there; Might be needed somewhere.
Modification of a flashlight from AAA batteries to 18650 battery

Thus, we “transferred” this device from three batteries to one, equal in voltage, thereby saving ourselves from the tedious charging of the power supply with small and low-capacity batteries.
Modification of a flashlight from AAA batteries to 18650 battery

The above changes did not in any way affect the quality of the flashlight (brightness and water resistance). Except that it has become one and a half centimeters longer.
Modification of a flashlight from AAA batteries to 18650 battery

Watch the video


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Comments (8)
  1. northwest
    #1 northwest Guests 14 November 2018 08:46
    2
    Does this flashlight have a lithium discharge controller?
    1. boyfox
      #2 boyfox Guests November 14, 2018 11:41
      2
      Of course not. The battery is a technical one, not a household battery.
  2. boyfox
    #3 boyfox Guests 14 November 2018 09:49
    4
    This is tough, comrades! The flashlight is damaged, which is a pity.
  3. Guest Alexander
    #4 Guest Alexander Guests 14 November 2018 20:59
    2
    So why all this gemara? You can order batteries for a flashlight from China, cut off a piece of metal-plastic pipe for 15, that's all. Battery Descriptions:
    Model: 14500
    Battery capacity: 2500mah
    Battery voltage: 3.7V
    Rechargeable: Yes
    Battery type: Li-ion

    Characteristics:
    Yellow color
    Size: 4.9 x 1.5cm (H x D)
    1. bones
      #5 bones Guests November 16, 2018 07:23
      2
      I converted this flashlight (for the frontal one) to 18650 a long time ago. I actually charge it with a separate charger for this battery. Enough.
  4. Leonid
    #6 Leonid Guests 5 December 2018 18:54
    4
    Very difficult. A similar alteration can be done differently. There are such LED flashlights in metal cases on sale. Moreover, the diameters of the housings are such that one fits into the other quite tightly. The conversion technology is similar, but the housings can be sawed off carefully with an ordinary hacksaw. After assembly, the final length of the flashlight is fixed with heat-shrinkable black tubing. View - you can't dig it. Good luck, craftsmen.
  5. Vladislav
    #7 Vladislav Guests May 30, 2020 00:10
    3
    There are also 18490 and 16340 and 15266, well, why bother sawing a flashlight in order to stick 18650 in it, explain to me, I’m a fool, I don’t understand it, but in extreme cases, you could use Ni-Mh pinky batteries
  6. Leonid
    #8 Leonid Guests December 5, 2022 09:55
    1
    I redesigned the same flashlight for 18650. However, I did not touch the housing, but moved the front board forward by about 6 mm. This was enough to accommodate the battery. There is, of course, more fuss.