Developer Brian Peterson has brought a classic Epson ActionNote 4SLC2 laptop back from the brink, enhancing it to include some period-appropriate upgrades and building a brand-new 3D-printed battery pack so it can once again compute on the go.
"This is just a little [pastime] project that I finished a few weeks ago," Peterson explains. "It is a restoration project for the [Epson] 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 coprocessor. 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."
With the ActionNote family of laptops having launched in April 1993 and been discontinued in 1996, though, a battery isn't the sort of thing you can just pick up from Epson's spares line — and any original batteries available second-hand will have long since lost their ability to store anything near a useful charge. To get the laptop computing on-the-move again, Peterson needed a new battery pack — so set about building his own, opting for an external "Charge Pack" rather than internal batteries.
"I purchased some Li-ion batteries [and] simply soldered them together," Peterson explains, "then 3D-printed a simple enclosure that I designed in Blender. 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."
The resulting "Charge Pack" connects to a barrel jack soldered to the original battery connectors, and is treated by the laptop as if it were an original set of internal batteries — complete with a necessary workaround. "The 27k Resistor from the positive terminal is to 'fool' the thermal sensor," Peterson explains, "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."
More details on the build, which can power the laptop for around two hours when fully charged, are available on Peterson's Hackaday.io project page.