HP-41 Battery Replacement

thingiverse

A 3D printable HP-41 battery replacement is available using 4 sub AAA NiMH cells or opting for the pro version that can be powered by either 2 AAA NiMH cells or an old Li-Ion mobile phone battery, which is USB chargeable. The link provided offers a detailed description of this project. Remember to use only "old Li-Ion phone batteries" as they come with integrated protection against short-circuits and undervoltage. Three different battery cases are designed: a two-part standard version, an open-top single part version, and another open-top single part version with a charger hole. The latter two are suitable for NiMH operation while the closed, two-part version is ideal for old phone batteries. Note that the single part case, as well as the bottom part of the standard, two-part version, require support structures for an overhanging edge and two snap-in detents. For a more detailed explanation, visit the provided link.