I recently bought a used Zelda and realized that it still saves perfectly! How long do NES and SNES batteries last inside the carts? Do the batteries get recharged when on or they only run when not in use? I read somewhere that N64 carts used a different system that within time would fail to save. Is this true? If so I better buy another Zelda or look for the Masterquest for the Gamecube.

I think it's 15 years or something, but you can get replacements on Nintendo's site still, maybe.

N64 carts use nonvolatile flash ram, which lasts practically forever without power.

NES and SNES both use a ram chip powered by a CR2032 lithium battery. The battery is spot-welded to terminals which are soldered into the board, but I'll bet you could use a small thin screwdriver or similar implement to break the welds, then "glue" a new battery in place with a couple dabs of silver epoxy. Failing that, just unsolder the terminals from the board, and replace with plain wires, and attach the wires to the battery using silver epoxy (observing polarity), then just tape the battery to the inside of the cartridge somewhere.

I've never had a battery die though, my NES Zelda cart still saves perfectly too.

The above post is true. Sometimes it just depends on the cartridge. All my SNES games save perfectly except one. I've been too lazy to open it though and replace the batteries.

When you do decide to do that, goto Radio Shack and get the battery holder for it. Save all the time in having to do it over and over again. It is a lot easier to do it that way. I use to work for the company and I have done a lot for people in these instances. They love it being able to change the batteries when they die. Especially when they are just getting back into the older games that they haven't played in a long time.

Those Zelda batteries are an amazing story. When the carts came out, they were given a 5-year lifespan. We are now past the 20-year mark and many are still going.

I guess Sony didn't make them, huh? ;)

-Dan

Vampmike, you used to work for NoA or Radioshack, and do you happen to have the part number?

Although all my NES carts still work perfectly, I have a few SNES carts that have failed, and I've found it pretty easy to replace the batteries myself. They just use a standard CR2032 coin battery that you can find almost anywhere. You have to have a special screwdriver bit to open the cart (available for about $5 on eBay -- search for 3.8mm gamebit), or you can take a Dremel and make a straight slot in the head of each screw, then use a flathead screwdriver to get them out, which is what I did a couple of times before I got the special bit.

Once the cart is open, you have to de-solder the original battery. It will have thin metal contacts welded to its top and bottom sides that lead into the circuit board. You probably can't weld new contacts to your replacement battery, but fortunately you can just solder a couple of stiff wires to it instead. You have to get the whole battery pretty hot for the solder to stick, and I was worried that it might damage the battery the first time I did it, but it seems to work fine. Then just solder the new contacts back into the board, clip of any excess wire if they're too long, and reassemble the plastic cartridge casing.

Here a picture of a spare battery and contacts I made for the next time I have to change one out, with one wire soldered to the top and another to the bottom:
http://homepage.mac.com/sidb/images/cr2032.jpg
I didn't think of a battery holder. If you can get one that fits in the cart, that would be even easier, since the hardest part is making the contacts to attach the battery to the circuit board.