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HP Forum Archive 08

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41's batteries contacts corroded
Message #1 Posted by Vieira, Luiz C. (Brazil) on 10 May 2002, 10:28 a.m.


I donít know if it happens with any 41ís owner, but letís expose the browse: BAT/IO assyís oxidation.

Besides the fact that it is hard to find N-size cells in here (rechargeable? NiMH? People havenít even told about it...), the available ones tend to leak and corrode the terminals, what is by no means desirable.

I am trying to find out a solution for this, if there is one. I am about to wrap the exposed parts of the batteriesí contacts with a thick piece of aluminum paper (what is the actual name for this in English?) but I do not know what sort of chemical reaction would result from this, say, golden-plated copper and aluminum in physical contact. Is there any other procedure to avoid contactsí corrosion? Can anyone tell me if wrapping the contacts this way will lead to good results?

Thanks for any answer..

Re: 41's batteries contacts corroded
Message #2 Posted by Ellis Easley on 10 May 2002, 5:40 p.m.,
in response to message #1 by Vieira, Luiz C. (Brazil)

The term is "aluminum foil" in the U.S. One thought that occurs to me is that aluminum is easily attacked by alkaline solutions (alkaline batteries contain a strong solution of sodium or potassium hydroxide) so aluminum might not be a good choice to contain a leak.

I was told that the reason alkaline batteries tend to leak (why they seem not to be getting better) is that in the competition for the highest storage capacity, manufacturers have reduced the wall thickness of the steel container (which I think is actually the positive electrode, unlike carbon-zinc cells where the zinc can is the negative electrode). So now the steel can is more likely to corrode through (although I am not sure the steel can is consumed by the necessary chemical reaction as the zinc can is) or less able to maintain the seal at the other electrode. The seal needs to be able to withstand the pressure of accumulated hydrogen until it can be converted to water (either by reacting with or being catalyzed by manganese dioxide). Hydrogen is produced in proportion to the current drain, so I don't understand why cells will leak maintaining the constant memory in a 41C or a 71B. It seems to me that the better alkaline cells have a more extensive seal at the negative terminal which is composed of a circular crimp and a heavy ring of insulating material around the flat button of the negative terminal.

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