|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.