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Some cartridges on older consoles (like on the SNES) had battery save in them, so you can turn off the console, come back some time later and continue where you left off.

These use an actual battery that powers the RAM so it basically never turns off. But does that mean it can deplete over time? If so, how long can these last?

  • 1
    Somewhat related: retrocomputing.stackexchange.com/q/124/12 – user12 Jan 17 '17 at 16:40
  • These absolutely do deplete. It may already be too late to recover your pokemon. (I had a Tetris cartridge in high school that wouldn't save high scores and I didn't [at the time] know why) – Random832 Jan 17 '17 at 19:24
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Yes, they can deplete. More modern games (starting with the Nintendo 64, for instance) used EEPROM (similar to flash memory) so don't have this issue, but in the days of the SNES this was too expensive so battery-backed SRAM was used.

How long the batteries last depends on the game. Pokemon Silver for example has a real-time clock, which takes a lot more power than SRAM alone, so all copies of it you'll find will either have already run out, or had the battery replaced at some point. On the other hand, games that just have SRAM might still be going strong today. But if your save game is important to you you definitely shouldn't rely on the battery lasting. Use one of the many methods available to back it up.

After making a backup, the battery can then be safely replaced without risking data loss. Most of these batteries are soldered in place, unfortunately, so it's not always easy to change them; you can often solder in a battery holder to make future replacement easier, if there's enough space in the cartridge. Most of them are CR2032 or the very similar (and often interchangeable) CR2025.

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    Some people hot replace the batteries rather than making a backup. And on interchangeability, CR2025 is smaller [so less capacity, will have to be replaced sooner] and may not fit snugly in CR2032 sockets. – Random832 Jan 17 '17 at 19:27
  • It also seems to depend on how frequently the game is turned on. I have a copy of Earthbound that loses its save if you don't turn it on for a few months, but will save religiously if you play every day. – phyrfox Jan 18 '17 at 5:09
  • @Random smaller batteries don't mean they hold less, only maybe if they're from the same time – Bálint Jan 18 '17 at 7:54
  • EEPROM was already used for some Famicom (NES) games, but more rarely. – Bregalad Jan 18 '17 at 8:22
  • @Random832 indeed, and I've had some success with that hot-swapping technique retaining data (SRAM tends to last a little while without power before decaying), but I wouldn't rely on that working for a game where I really cherish the save. And yes, you're right about CR2025 being smaller of course, hence why I said "often interchangeable" ;) – Muzer Jan 18 '17 at 9:35

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