USB powered "fake" battery pack adapter?

[Maximilian Hohmann]

Why not simply buy four rechargeable AAA and four AA cells (Aldi or Lidl in Germany sell them for less than a Euro a piece with 1200/2400 mAh capacity) and a fitting charger? They last for months in a Voyage 200 and similar calculators. No need to tinker around with USB chargers...

As far as for the Ti59 you mention one could certainly remove the dead cells from a battery back and connect a USB charger to the battery leads instead. Maybe with two silicon diodes (1N4001 or similar) in between to lower the voltage from 5V to slightly below 4V. But honestly I found it easier to replace the cells in the pack with modern ones (they have twice or three times the capacity of the original cells) and just use the calculator as it was intended to be used. One good pack is enough for my whole collection, the one that fits the Ti58/Ti59 is also good for the SR-56, SR-52, SR-51 and many others.