Power supply for HP computers with Woodstock case

[Tom Flatterhand]

As part of my recently purchased HP-25 and HP-29C, I've been looking into the future power supply for the two calculators. Probably most of you here already know the best way to do this. But in case you don't, or for newbies, I'll summarize here what I found out:

For 3D printer owners, Thingiverse has an STL file for a battery/battery case that fits the Woodstock case very well:

https://www.thingiverse.com/thing:1276886

Presumably based on this STL file, you can order this case in different variants at Shapeways:

https://www.shapeways.com/product/6NQAST...ery-holder

The 'problem' of this case, just like the original case, is the fact that modern batteries like Eneloop only fit in very tightly and therefore put a lot of mechanical stress on the case. This is because many AA batteries are around 50 mm long. Eneloop for example 50.5 mm.

Instead, I found a battery (NH GP 130AAM) at the German company Reichelt, which fits perfectly into this case with only 48.2 mm:

https://www.reichelt.de/de/en/nimh-indus...os_0&nbc=1

Moreover, it has with 1300 mAh about twice the capacity of the original battery!

At least 2 levels further is the solution from 'pwr', who has developed a battery/battery case suitable for the Woodstock case, which allows wireless charging and contains a modern lithium battery. Unfortunately, probably not so easily doable for most of us:

https://partsbox.com/blog/wireless-charg...-2021.html

Bilder:

Das weiße Gehäuse ist das von Shapeways. Das graue und das goldene Gehäuse habe ich selbst ausgedruckt.