Please do not be a meanie (can't say cuss words on here) and say that everyone knows why they wont save because not EVERYONE knows this.

Okay so for years I tried to figure out why my Pokémon Gold, Silver, and Crystal suddenly stopped saving. After years of searching I was told the answer by my friends dad who is an employee at Nintendo. First I will tell you how he told me with a story.

I was at my friends and we were trying to play Pokémon Gold, Silver and Crystal with a GBC link cable. We were getting frustrated that our games wouldn't save even though the game said "GAME SAVED." I finally yelled loud enough to be heard throughout the house as my friends dad was walking by. He asked what was wrong and I said, "What's wrong is that my Pokémon games have broke and won't save anymore. So now I have three useless games in my collection." He asked me which ones and I showed him. He took them and he said he would be back in 10 minuets. 10 minuets later he was back with the games. He said put them in and try to save, turn it off then back on and see what happens. I did as he told me and boy was I shocked to see what was before me. My game had saved! I asked him how he did it and he showed me a package and a battery and said I just gave the game anew battery. He then showed us how he did it.

So for all those people out there who didn't know, well now you know. The game has a battery and it needs to be changed. To change the battery go here. Please let me know if this helped anyone out.

This is not a new thing though exactly, since this is the case for many GB, GBC and GBA games as the battery is used for saving the game.
This was changed with the DS era though.

Anyways don't know if this is something you should post here as I don't think there's much to discuss about it without going off topic. Nice story though

Wow, that's actually pretty cool! I didn't know that some game cartridges have batteries in them as well. I learn something new everyday! 

mangalover9x9 : This is actually quite common for the old Pokemon games. The batteries stop working after years of wear and tear on them. On top of that, of people that own these games know that the batteries can be replaced. I assumed that this was common knowledge among Red/Blue/Yellow and Gold/Silver/Crystal players.

nreid1 : That may be the case, however, there are still some people who don't know and I wish to help them.

The batteries on the 2nd gen Pokemon games tend to die out a lot quicker when compared to other Game Boy cartridges as it has to constantly supply power to the internal clock. I've replaced the battery on my gold cartridge about 4 or 5 times because of it. But there's this device I've been using so I never loose my 150+ hours of progress if a catastrophe happens: http://www.amazon.com/Mega-Memory-Card-Game-Boy-Color/dp/B00002R108

I bought mine about a year or two ago for $15, but it seems the price has exploded since then...

Yeah, that sucked, I had all Pokémon on my original gold, and a hellalot of shinys 2 , they noticed this and that's why Gen 3 was so butchered in the terms of the clock mechanics.