Some time ago I bought two lights (made in Japan) that are led lights with a motion detector that automatically turns them on when someone enters the room or moves. They stay on for 15 secs if there is no movement and they also won’t turn on if there is other light. I installed them in both our toilets, in case my wife enters and forgets to switch the light on.
I noticed that one of them was not working and on inspection found that it had been switched to be permanently on. That means I had turned it on and forgot to turn it back to auto. But, because it was on all the time the batteries ran out. I took it down and opened it to replace the batteries and found that one of them had gone bad, it was leaking acid. I took it to the sink and washed the acid away. Bad mistake, the water somehow got inside the sealed compartment and I could see droplets in there. I left it for a few days to dry out, but it did not.
So I decided to take it apart and dry it. I opened it up with care and wiped it with a tissue and then left it to dry. Then I went to put it back together again. As I was doing so I noticed a wire sticking up with no connection. By inspection I realized that this was a major connection to the battery compartment that had come loose. I needed to re-solder it. But, I had thrown my soldering iron away (I had brought it from the US and kept it for years, but of course when I needed it it did not work here, different voltage). So I asked my son-in-law Jeff to borrow his soldering iron.
With trepidation I heated it and then soldered the thin wire back to the connector. It held, so elated I started to reassemble the device. But, there was a large O ring seal inside the sealed compartment, that I had to manipulate around the circumference. But, I could not get it to stay. So I used a few tiny dabs of glue to hold it in place. Then I reattached the top and screwed it down, et voila. But, not so fast.
As I was replacing the batteries, I discovered that the one that had leaked acid had corroded the spring that sits at the bottom and holds the battery in place and makes contact. The new battery would not fit, it was loose. As I was trying to release the spring it simply broke off, it was so corroded. What to do? I searched for a small spring among my collection of screws and trivia and in fact found one, but it was about 5 times too big.
At that point our Filippina carer Sahlee, who was watching me, casually remarked, “why not try foil.” She said she had been advised to use this to make battery contacts when she worked in Taiwan. So we took a strip of silver foil and folded it to fit the space between the battery and the contact and lo and behold it worked. The light turned on, and when I tested the automatic switch it turned on in the dark with the motion detector and then turned off. So once again human ingenuity had triumphed over the forces of evil and chaos.