Battery dead but not replacable - What now?

It happens a little bit too often; stuff that you used for one or several years with much pleasures, just stops working. Battery dead! Well, yes, the built in rechargeable battery won't charge anymore. One thing you could do is to give in to it and buy something new. But what if you refuse to throw away your favorite item that you re-charged less than 50 times? Or what if the item cannot be bought new, because it was only sold for 2 years? Well, fix it! In the age of the internet you can now find a solution to almost any problem, including how to repair or replace dead batteries for many items.

I would like share the case of my mp3 player. It did not charge so many times and just stopped working. I found several instructions to it (my main source seems dead, but this one is also good) and it was so interesting that I decided to try it. The short explanation: a too long battery pause can cause a hardware switch to set the battery in inoperable state. This switch can be undone by de- and re-solder the battery. In this case you don't need a new battery at all! So I tried:

I soldered it back on, I put it back together, and plugged it in for charging.
And guess what? It worked!
It took me only 20 minutes (and no ordering of new batteries) and was definitely worth doing!

There was another item I wanted to fix, which many of you may have: an Oral B toothbrush with a dead battery:

 

And there are many manuals online that show how to replace the battery: Here, and here.

A new battery costs about 10 Euro/Dollar and the replacement is quite tricky, but can be done with patience. It will take about an hour...
And than I considered the following: It is an hygiene item. The bottom side is really full of microorganisms such as algae that got in the rubber and cannot be washed out... Also the grip got more difficult to clean. And it should be clean, you stuck it into your mouth...! I admit, in this case I bought a new one for 20 Euros and saved an hour of messing around.
I really wonder, who makes these pervert designs? It should be no problem to earn money with the replacement brushes and make the electric holder partially out of metal for more easy cleaning. And the bottom out of plastic with a screw system for easy battery replacement. Technically no problem at all! You then could easily use your toothbrush for 10+ years without causing extra waste.

Well, anyhow, many thanks to all the people who write these repair manuals!! I will post more of my successes in the future.