Black & Decker Spotliter flashlight convert to 18650 lithium cell with USB charge board, flashlight holder

I had this old Spotliter with no charger. I replaced the old cells with an 18650 holder and used one of the original charger ports to mount the USB board. Other items needed are two 3mm buttonhead screws, two nuts, 6mm wide metal strip, micro or C charge board (Amazon), 18650 cell, wire, hot glue. The nickel metal strip I used is for spot welding cells together.

Strip everything out of the light. Insert charge board holder all the way down and over into the slot and square up in the slot. Hot glue it down making sure you don't get any glue where the board sets. If using the USB-C the other side of the slot will need to be filed out wider. The center contact piece old wire can be cut off and a small wire solder on long enough to reach the board. Hot glue it back into position. All wires should be a generous amount. This allows for easier wiring and soldering. The battery holder consists of two parts that screw together. Put the buttonhead screws to the inside and screw each in the plastic. A wire is nutted on each part. The larger diameter part goes down the handle so give a generous length of wire to reach the board. The metal strip goes through the side slot and each end pushes down into the recess and glued down. The slot may need to be clean out to allow the strip to go through. Note where the switch contact meets the strip and solder a wire to the other section. The switch contact should be bent down slightly to make sure it makes good contact when the slide switch moves over it. The charge board extends to high up for the light cover to fit. File a small relief slot for the board (pictured).

It makes no difference which way the cell is put in as long as the wires are connected correctly. Insert 18650 cell into tube and tighten lightly. Too much pressure could cause it to split on the thread layer lines. If it does try clamping it together and hot glue the halves. Thread wire through cap side when putting it on and insert assembly with the large section down into the handle. Turn cap into slots to lock in place. With all four wires soldered to their components, time to solder to board. This is wired with the prospective that the cell's positive terminal is at the cap. The center bulb conductor is soldered to OUT+. The wire from the slide switch conductor is soldered to OUT-. The wire from cap side cell is connected to BAT+. The wire from bottom cell is connected to BAT-. Slide board assembly into holder and hot glue. Instead of the original bulb I purchase a three-watt 200+ lumen LED replacement from Amazon which is optional. 

All printed parts were made from generic white PLA. I used 0.20 layers, 4 walls for better thread layer strength, 30% infill

Note in pictures: The red and black wire needed to be reversed. I discovered this after taking picture.

10/27/2026: Holder revision. I asked my wife to get the flashlight and by doing so she lifted in up and out instead of straight out causing the latch to get sprung and weakened. The new holder has a limiting cover incorporated that prevents this from happening.