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I want to preserve my trusty HP-42S (serial number 2841A12776) as future backup, because now I use the awesome "go42s" app by Olivier De Smet in my android device.
I've removed the batteries as a precaution in case the batteries do leak (since june), but I've heard that it might be prudent to actually leave the calculators stored with batteries inserted for long periods of time.
Is it true that it's better store this calculator with the batteries? and in this case, why is the reason for that?.
Also I keep stored without batteries my HP-12C, HP 48S and my HP 50g.
Can anyone give me some advice on what to do please?
Thanks in advance.
Waiting your answers,
Best regards,


For long-time storage, I'd generally remove the batts to avoid leakage. There are many HP calcs dying the battery acid death, so there is no alternative if you don't look after the units on a regular basis. However it may be helpful for some hardware parts to get some electricity from time to time (say twice a year), but the hardware guys may have more info about this.

Actually I had a NIB HP-42S which had not been powered on for more than ten years, and which worked flawlessly when putting in new batts some time ago.

Every HP calc family has its own special deficencies, to my knowledge independent from the battery. The Pioneers suffer from shrinking foam connector pads, the HP-41 series mainly from battery acid damage. The Woodstocks weren't made to last: Fried ACT ICs are very common, due to connecting the AC adapter w/o working buffer battery. No coated pcb traces, prone to catch battery acid or other corrosion. Similar with the Spice series units. The Classics (incl. the Woodstock 67) sometimes have LED problems, and so on.



IMO, all hp calculators should be stored with batteries removed as all batteries will leak when they fully discharge. The risk of leakage, by far, exceeds the very slight risk of capacitor failure due to lack of forming voltage.

Overall, the capacitor risk is incredible small and only applies to some of the models where there are high capacitance standard aluminum electrolyics. This would include later models of the 41, the 48 series and the models that followed them, time-wise.

Pioneers and Voyagers have a very low component counts so they are the most likely devices to survive long term storage. FWIW, Pioneers have no aluminum electrolytic caps, early Voyagers had one small value cap that was later was changed to tantalum - which do not dry out so they should be good for the long term.

Do not store in a bag to reduce the chance of condensation and provide stable temperature and humidity levels.

I've some questions for you:

- Is it a good idea keeping the calculators (inside their respectives cases) in my desk drawer with little packets of silica gel?

- Are you controlling humidity parameters?

- What's a reasonable value?, less than 30%?

I'll be very grateful if you can tell me your opinions.

Best regards,


IMHO, it's perfectly safe to store them in ambient conditions on a shelf in a room - at least I do it for over a decade. Classics, Woodstocks, Spices, Voyagers, Pioneers, whatever. No problems with humidity in Central Europe. Batteries are far more important!

BTW, I won't put them in their cases or pouches or even in a drawer - I want to enjoy looking at and playing with them.

Just my 2 cents.