So, about potato cleaning. Cook or no cook before clean? It must be no cooking before using it to clean. Sprinkle generously with baking soda, then rub away. Actually, sweet potatoes are more effective because they have a higher concentration of oxalic acid. Also, carrots have an even higher concentration, but they may be more difficult to work with.
Potato 0.05 g/100 g
Sweet potato 0.24 g/100 g
Carrot 0.50 g/100 g
20180522/DuckDuckGo potato oxalic acid
20180522/https://chemistry.stackexchange.com/questions/7079/how-to-test-oxalic-acid-in-potatoes
20180522/https://en.wikipedia.org/wiki/Oxalic_acid
20180522/DuckDuckGo potato clean corrosion electronic battery
20180522/https://www.wikihow.com/Remove-Rust-and-Corrosion
Now, some of my contacts could just as well be iron, but others are almost surely nickel. Is there a separate cleaning method for that?
Also, some are for sure brass/copper. Purportedly you would use similar cleaning methods for that.
Ah, the famed method is to use electrolysis to remove corrosion.
20180522/DuckDuckGo cleaning corrosion off of nickel
20180522/https://www.cointalk.com/threads/how-to-get-corrosion-off-nickel.50305/
20180522/https://en.wikipedia.org/wiki/Electrolysis
20180522/http://www.instructables.com/id/High-Quality-and-safe-Nickel-Plating/