The Museum of HP Calculators

HP Forum Archive 04

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Calculators Storage
Message #1 Posted by Y K Wong (Singapore) on 26 Sept 2000, 8:35 p.m.


While it sound strange to store a calculator instead of using it, but most of us that visit this Forum probably have one too many calculator than we need and yet cannot bare to dispose them (or rather some of us keeping them as a collection!). So what is the best way of storing a brand new and a used/classic calculator? Should the battery be removed while storing, however, will the calculator still be able to power up say years later? I tend to keep my calculators with their respective batteries and keep a check on a regular basis to ensure functionality and leakage, however, due to the weather here (hot and high humidity), I am thinking of sealing them in individual airtight bag with silica gel. Thank you.

Re: Calculators Storage
Message #2 Posted by Viktor Toth on 26 Sept 2000, 10:25 p.m.,
in response to message #1 by Y K Wong (Singapore)

Should a battery pack be removed from the calculator in storage? Yes, absolutely, at least when it comes to vintage calculators and rechargeable packs.

One of the problems with old(er) NiCd battery packs is outgassing; specifically, slow outgassing of KOH gas. This gas can cause problems in a variety of ways.

First, KOH usually reacts with CO2 from air, forming potassium carbonate (white crystalline stuff near the battery terminals.) This stuff is fairly harmless, but the by-product of this reaction is water. The resulting dampness, in the presence of the battery voltage, can cause an electrolytic reaction (blue-green stuff appearing on copper surfaces, for instance.)

Worse yet, in storage it is possible that there's insufficient ventilation, especially inside a calculator. The CO2 content of air is low enough to begin with, and when it's exhausted, any more corrosive KOH gas will start to directly attack metal and plastic parts (black corrosion.)

An airtight bag makes this problem worse. Silica gel helps a little since it may absorb some of the moisture, but unless you put it inside the calculator, it'll only be good for absorbing environmental moisture, not moisture generated inside the machine. Lastly, I don't think it absorbs KOH, which can cause far more damage.

So the bottom line is that unless you use a calculator regularly, it's probably a good idea not to store it with a NiCd battery pack inside. (It *is* probably okay if the machine is taken out and used once or twice a month, and when that happens, you also remove the battery pack, "airing" the battery compartment while at the same time checking for the presence of early signs of outgassing.)

Alkaline and other non-rechargeables do not have this problem but they can still release an ugly goo that can damage a calculator. The release can be fairly sudden; one week, you see no signs of leakage, the next week goo is already present in the battery compartment. The good news is that, although I have no idea what it's made of, the goo from modern alkalines appears relatively harmless, and it can often be wiped from a battery compartment with virtually no residue and no damage done.

I have not yet seen leakage from 3V lithium and 1.5V silver-oxide batteries. Since there are HP Voyagers out there that reportedly still have their original set of silver-oxide batteries after 12 years or more, I think it's safe to say that those batteries present almost no danger of leakage.


Re: Calculators Storage
Message #3 Posted by Y K Wong (Singapore) on 26 Sept 2000, 11:39 p.m.,
in response to message #2 by Viktor Toth

Thanks Viktor,

I have a 16C that I bought 15 years ago that I kept brand new in the box, the original set of batteries lasted till recently (in fact last month) before I have them replaced 15 years! Yes, no problem at all, no leakage and the contact is as nice as new! However, my concern is with those older models such as Classic, Woodstock, Spice and perhaps including Coconut (i.e. 41Cs), if I would to remove the battery now after they have being running for so many years, what would the possibility that they may not be able to fire-up again years later? My bad experience was with my PC where I run it for years without any problem, however, once I have shut it down for a few months, it just dont wake up anymore!

Thank you.

Y K Wong.

Re: Calculators Storage
Message #4 Posted by M Currie on 27 Sept 2000, 12:34 a.m.,
in response to message #3 by Y K Wong (Singapore)

I can't see where leaving the batteries out would harm a calculator or keep it from restarting. A computer is a little different, since it has a backup battery that can go dead after long inactivity, and occasionally a hard drive can fail to spin up after a long rest, but assuming a calculator has neither of these, it shouldn't be an issue.

Re: Calculators Storage
Message #5 Posted by Viktor Toth on 27 Sept 2000, 12:43 a.m.,
in response to message #3 by Y K Wong (Singapore)

I'd say that the presence or absence of batteries has little or no effect on your ability to power it back up at a later time. On all but the continuous memory models, no part of the calculator is powered when the power switch is in the OFF position, so the battery might as well just not be there. On continuous memory models like the 25C, the RAM is powered at all times, but this will actually drain your NiCd battery pack, possibly contributing to the outgassing if any of the cells in the pack are deep discharged and then reverse charged. In any case, whether or not the RAM is powered has no effect on the calculator's ability to "wake up".


Re: Calculators Storage
Message #6 Posted by Y K Wong on 27 Sept 2000, 1:29 a.m.,
in response to message #5 by Viktor Toth

Thanks.... I understand now!


Y K Wong.

Re: Calculators Storage
Message #7 Posted by Chan Tran (US) on 27 Sept 2000, 10:49 p.m.,
in response to message #6 by Y K Wong

The batteries should be removed. If you are going to store your calculator away for a long time. When you power up your calculator the battery is bad any way

Re: Calculators Storage
Message #8 Posted by Mike Sebastian (US) on 28 Sept 2000, 12:26 a.m.,
in response to message #7 by Chan Tran (US)

A few personal observations:

I have purchased several old calculators that had been stored for a significant period of time and had their ni-cad batteries leak. The damage is usually significant, and often fatal to the calculator.

The so-called environmentally friendly alkaline batteries that have been marketed since the mid-90s have a relatively short shelf life. And, like Victor mentioned previously, they can leak suddenly. While the damage isn't as severe as that caused by ni-cads, they can still cause irreparable damage to a calculator or other electronic device.

While silver oxide button cells have excellent storage characteristics, many calculators now only come with alkaline button cells. All the caveats above regarding alkaline batteries still apply, although the damage us usually not as severe simply because the volume of material which leaks is slight.

I've never seen a lithium coin cell leak.

Bottom line: except for silver oxide and lithium cells, I would not recommend leaving batteries in a calculator stored for any significant length of time.

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