Introduction: Old to New Flashlight

About: IT guy with DIY as a hobby ;)


After a long time of absence and a lot of minor projects, i would like to show you my last project. I`ve done it in about 2 hours during boring (still winter) evening.

Do you remeber old fashioned flashlights , powered with 4,5V battery and a weak light ? Of course - most people older than 20-30 had it at home ;) I wanted to bring it to life again, and give it more power than it ever had .

So if you have a few unneccessary things and two hours of time - let`s start.

Step 1: What We Have Here ...

As a IT guy and RC modeller who wants to be an electronics guy, at the same time... I found these things in my drawer:

- old flashlight

- 12V Led bulb

-18650 x3 - cells from old battery laptop

Of course you will need some tools too. I used:

- soldering iron

- grinder Dremel

- balancer cable (to get one plug )

- soldering acid (to faster soldering 18650 cells) - not neccessary but it easier to solder using it.

Step 2: Battery Pack and Bulb - Preparation

I made a battery pack with plug for balancing. I soldered cells together in series.
Of course you can use any 12V battery pack which will fit physically into old flashlight. Then i had to cut a ring from led bulb to fit it into yellow socket. I took led converter from led bulb , outside and glued it to housing , at the same time extending the cables to leds. At the end I connected power cables from battery pack to old,original switch.

Maybe this is not the "super-clear" project inside , but how i said - done in 2 hours to pass the time during boring evening.

Step 3: Charging

I wanted to keep this flashlight look like an old one , so i left all connectors inside. Balancing/loading plug is inside between baterry pack and housing on a few cm long cables.
After closing the housing it looks like old good stuff (except the led bulb of course)

Step 4: Final Test

Was it worth of these 2 hours of my live ? I think YES :)

Despite the fact i find a pleasure when making things like that , take a look at photo taken in my basement. Weak light - old 4,5V bulb and very strong light on 12V Led bulb. Somebody may say - it is hard to buy 18650 cells in shop on the corner - most people still use AA or AAA battery ... Yes , but i have many flashlights and many chargers - years of beeing RC modeler did my drawers full of that kind of stuff.

And many people use 18650 in e-cigarettes, so 18650 are every day more and more accessible in many kind of shops. I like them because of capacity and current they can give.

As an upgrade i plan to add BMS or cells protection in future, because now led is connected to battery pack directly without any protection from over discharge.

That`s all.

See you next time