This is just a little pass-time project that I finished a few weeks ago. It is a restoration project for the 4SLC2-50 Laptop sold in '93. I did the routine upgrades to the unit, 8mb ram, 500mb HDD (the largest it can take) and a 387SX FPU 16-25MHz Co-Processor. Those parts were found on Ebay and a reasonable price except for the ram upgrade, that had to be hunted down myself. The only thing I was missing is a battery, so I purchased some Li-ion batteries from:

Simply soldered them together (diagram provided here), I then 3D printed a simple enclousure that I designed in Blender.
The 3d Model is found here:

(above link fixed)

The 27k Resistor from the positive terminal is to 'fool' the thermal sensor, otherwise it thinks the battery is overheating. These batteries do charge fine with the laptop however they may overcharge since they never reach their target voltage, it is recommended that you stop charging at 3 hours and 30 minutes. The batteries will last more than two hours at full charge.
These batteries in particular will not simply fit inside the unit, this is why I just made a "Charge Pack" that I can just plug into the laptop. This makes swapping batteries easy should this be needed to do. This project is by no means a professional job, just a passtime, I selected this laptop in particular becuase it was my very first and has some sentimental attachment.

Transfering files to/from an old PC that only has a serial port:
I bought this cable to coneect them together:
I am lucky enough to have an old copy of FastLynx 3.3 that I used for work a while back, you can buy it here:

Or find yourself another version via search.

One possible use for this is plugging in the DB9 serial port into a terminal node controller, I made one myself for BPSK Decoding a few years ago using an ATTINY85. I may post that later on.

A special thank you goes out to (themaritimegirl) on youtube who made a great video about the epson 4slc2-33 which did help out alot in this restoration. Her video is here: