HP Forum Archive 03

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Cleaning Up NiCad Mess Message #1 Posted by Fred Towers on 10 July 2000, 10:11 p.m. I just received a type 3 HP 35 in much better shape than I expected. However, the inside of the battery box is coated with tiny, shiny crystals. This has got to be (mainly) potassium hydroxide from the deceased NiCads. Two questions. 1. Is there any reason to not soak then completely dry the battery box cover? There are crystals inside the latches that make it hard to open and close the latches and crystals keep coming out of the latches. 2. How do I clean up the calculator's battery box? The serial number label and battery contacts are in really excellent shape, but I would like to get the minute crystals out of the battery box. They are almost like a thin film. How the battery contacts and serial number label came out so well is a mystery to me. Thanks for any suggestions. I've owned HP's since the early 1970's, but I always managed to get the batteries out BEFORE they made a mess. So cleaning up inside the battery box is a new problem for me. Fred

Re: Cleaning Up NiCad Mess Message #2 Posted by Viktor Toth on 10 July 2000, 10:22 p.m., in response to message #1 by Fred Towers Fred, If the crystals are white, they're probably potassium carbonate, produced when the potassium hydroxide from the battery reacts with CO2 from air. The good news is that this stuff is harmless, and most of it can be cleaned away using a small brush (I just use old toothbrushes) and compressed air. The nasty stuff happens when there's no more CO2 around the calculator (e.g., when it's inside a sealed case) and the KOH attacks metal or plastic parts; or when the presence of moisture (a by-product of the KOH+CO2 reaction) and electric current (from the dying batteries) causes an electrolytic reaction. Obviously, your machine has not yet reached that stage, for which you should be grateful. Viktor

Re: Cleaning Up NiCad Mess Message #3 Posted by Fred Towers on 10 July 2000, 10:47 p.m., in response to message #2 by Viktor Toth Thanks for the help. Just so I'm sure... You mean just a DRY brush? You are right, I had not though about the fact that potassium hydroxide will react with water and carbon dioxide and become far less harmful. Apparently this calculator was, by pure luck, stored right side up. Most of the crystalline mess went away from the calculator and on to the battery box cover. Is there any reason to not soak the battery box cover? It has the crystals in the latches and I can't think of any other way to clean up the latches. Fred

Re: Cleaning Up NiCad Mess Message #4 Posted by Viktor Toth on 10 July 2000, 11:29 p.m., in response to message #3 by Fred Towers Fred, Since one of the byproducts of the KOH+CO2 reaction is water (2KOH+CO2=K2CO3+H2O), and the K2CO3 crystals happily coexist with it without either exploding or burning a hole in the plastic, I say, go for it, soak any plastic parts. Just don't blame me if anything untoward happens :-) Personally, I prefer to use a dry brush and a can of compressed air (well, not air, strictly speaking, but tetrafluoroethane or whatever it is that's inside those cans of duster gas.) Viktor

Re: Cleaning Up NiCad Mess Message #5 Posted by Erik Wahlin on 11 July 2000, 12:39 a.m., in response to message #1 by Fred Towers Hi. The way I have cleaned up the battery box is to use a bead blaster with extra fine glass beads. This is done only if compressed air or 409 cleaner cannot remove the crystals. You need to cover the contacts (because they are gold plated) and serial # decal with tape. I realize that not everybody has access to a bead blaster, but just wanted to give you another idea. I believe it is important to use the extra fine mesh beads and to "lightly" blast the area (hold part 6-8" from blaster nozzel). My battery compartments look like new after this process.By the way, I usually do this when the calculator is dissasembled. If it is done assembled, the calculator needs to be taped up to prevent the glass media from getting inside the calculator.

Re: Cleaning Up NiCad Mess Message #6 Posted by Carlos Tolossa on 11 July 2000, 10:48 p.m., in response to message #1 by Fred Towers Guys, this is what I've done and it works: The dry brush trick is fine but in addition, I've used the vacuum cleaner to suck all the crystal from the inside of the case, (if interior of case is accessable, better yet..), then I used a sodium free battery acid neutralizer made by JV manuf. 800.334.9092. With a Q-tip, clean the areas that were exposed to battery acid, let it set for 5 minutes, this liquid will turn yellow when neutralizing and light purple when contaminating areas are neutralized. Dry it thoroughly. Then, before you close the battery compartment, insert a tiny bag of silica-sorbent in it (sold by Multisorb Technologies 800.445.9890). Case solved. I've used this trick on a lot of the Spice 30E/C series. and lots of 41C series. The liquid neutralizes and arrest corrosion on plastic or metal due to batt leaks . Legal disclaimer note..... I do not have vested interest on any of these companies nor the products they represent, read and follow product label instructions, use at your own risk, result may vary from case to case. Good luck...

Re: Cleaning Up NiCad Mess Message #7 Posted by Richard W. Smith on 12 July 2000, 11:42 p.m., in response to message #1 by Fred Towers In several instances, I have found that a cotton swab ("Q-tip") dipped in ordinary vinegar will remove battery deposits. I then make several passes with other Q-tips dipped in water to remove the deposits+vinegar. Finally, I swab on Radio Shack's "tuner cleaner" to lay down a protective coat.

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