1. Remove label of the back side and unscrew 2 screws with Philips #1 Screw Driver.
2. Open the slicing cover and remove it - just apply force to untrck.
3. Cut away about 17mm of top halves like photo. Cut a bit more edge side to fit in the 18650 Battery. I have used 4" Angle grinder for rough cutting, trimmed with cutter and finished with files.
4. Provide a negative terminal, possibely a spring metal but good normal >0.5mm tin plated steel sheet.
5. Make V cuts(@4 places) bottom side for heat-and-push-in with soldering iron.
6. Provide positive terminal in proper size and glue to the proper position. I have used a piece of sponge double side tape.
7. Soldering positive terminal to B+, negative terminal to B- and a 1.5kOhm 1/4W resistor between sensor terminal(middle) and B-.
8. Apply a piece of masking tape, not to make short circuit with the resistor.
9. Assemble it.
a) Because of the lost of one coupling part of the two halves, cutted side would be loose - apply a drop of super bond to secure it.
b) The 5V supplying micro USB connector should be connected after installation of the 18650 Battery. - Because of the soldered 1.5kOhm sensor curcuit, we are cheating the circuit.
The charger works perfectly because the similarities of the battery capacities, Gallaxy S and 18650.