Wednesday, January 15, 2014

Super Metroid SNES Cart Battery Swap (2014)

A short while ago, a great friend of mine purchased a used Super Metroid SNES cart.  However, he quickly realized the SRAM battery was shot, which meant the cartridge could no longer save his game.  I offered to see if I could swap the battery for a new one and give back the cart is functionality.

The first obstacle, I knew, would be the darn tamperproof gamebit heads used by Nintendo to keep their cartridges shut.  I had a piece of scrap aluminum around, and on the second attempt managed to file a passable makeshift gamebit driver.  (For my first attempt, I made the miniature spokes were too thin; because aluminum is so soft, the tool quickly bent out of shape.)

Makeshift hand-filed gamebit driver.
Fortunately, the cartridge screws are only very lightly tightened, and my improvised tool made short work of them.

One down.
One screw out of the cartridge.
Unfortunately, the tool lightly scratched one of the screwholes.
Then came time to have a look at the goodies!

Freshly-opened cart.
The culprit, a dead CR2032.
Look at that battery.  As Shijima said in Ninja Scroll: a strange technique!
The CR2032 is held in place using a manufacturing technique I'd never seen before.  After some research, I realized that you can purchase so-called tabbed CR2032 batteries which come with such tabs preassembled.  The tabs look like they're cold-welded to the battery casing in two spots; I presume this is done before the battery itself is even assembled, because it looks as though the welds on the bottom were made from within the battery.  The spots form a tight bond between the battery casing and the tabs, and it took quite some effort to separate them.

At this point, seeing as how it looked as though I would have to irreversibly deform the tabs when removing the battery, I decided to turn to the internets to see what others thought the best repair method was.  I found a few blogs pointing to the following page:

I thought: tape is an obvious solution, but surely a permanent battery holder would be a much better one!  And I happened to have one lying around from a discarded PC.  I removed the old battery and tabs, and tried the battery holder for fit.

Removed tabs.
Trying the CR2032 battery for fit.
Unfortunately, though it was elegant, this was not meant to work.  I quickly discovered there is not enough space inside the cartridge case:
FAIL!  Not enough space inside the cart.
Luckily I hadn't soldered the holder in place yet.  I simply removed it, soldered the tabs back in and taped the battery as suggested.  The new battery holds quite fast, and I preloaded the tabs with tension so the battery mostly holds in place even without the tape.

Tabs back in.
Battery in place.
I then closed everything up and tested the fix.  Victory!
Closing up the case.  (The soldering job looks terrible in this picture; it doesn't look nearly as bad in real life.)
Testing out the fixed cart with my furry assistant.
The galaxy is at peace!
Edit: seems there was possibly more to this cart's problems than the battery, since it just suffered another saved game reset.  To be continued...

Second edit: many thanks to reader Kincl, who pointed out that Super Metroid is apparently an ornery cart whose SRAM/battery circuit is difficult to restore to health!  It appears this is a somewhat common case:

For what it's worth, this specific cart has held up for just about a week now.  Time will tell how durable the repair ultimately was.


  1. See the thread about Super Metroid ( replacing the battery; it saving once but then wiping the save next time you turn on the SNES; possibly an issue with the SRAM? I researched this because I have just done exactly the same and suffered the same. If you find out how to get it saving properly with the new battery in place, please let me know!

    1. Wow, thanks a million for this information - glad to know I'm not crazy! It never occurred to me to check whether there was a problem with that specific game.

      I wonder what it is about that Super Metroid specifically that makes this problem of sporadically-lost saved games more likely... If it's the SRAM, then perhaps something in the programming is causing it to wear out particularly quickly. Otherwise, perhaps the capacitor arrangement is peculiar on that cart; electrolytics in particular wear out over a few hanfuls of years, depending on rating, temperature, voltage, etc. From looking at a few other forum posts, though, the only electrolytic cap on this cart is apparently used to decouple the board as a whole, so it seems unlikely to be the culprit here. (And this type of cap seems used on most, if not all, other games.)

      In my case, the cart seems to be holding the games now with about an hour of gameplay spread over a week. How long will it last? Only time will tell I guess :P Thanks again for the info!

    2. (PS: if I ever come up with a more solid solution than "cross my fingers", I'll definitely let you know :D )

      Also, just musing out loud, but now that I think of it, the typical failure pattern of SRAM due to wear and tear would probably just corrupt the saved games, not erase all of them at once... hmm... food for thought!

  2. Another tip, which you may already know: you can save immediately in Samus's spaceship when you land on Zebes for the first time, which means you don't need to slog your way through to the first Save chamber inside the planet. I wish I'd found this out earlier, before I tested the save multiple times after it kept on vanishing!

    1. Yes, thanks! I do actually know that, but I wanted to play for a few minutes, reboot, etc. to see if the cart held true... that's why there are nine minutes of play on the picture :D I did make my first few tests using that save point, however. Very useful!

  3. Lastly, I soldered in my new battery and the connection was secure. Have also done new batteries for FFVI and LOZ: LTTP in the same way and that's been fine with them.

    1. Was that with a pre-tabbed battery? I didn't have any on hand, and I was half-and-half on soldering directly to the untabbed CR2032. Tin generally doesn't bind well at all to stainless steel, and the electrolytes in these batteries are quite temperatures-sensitive... I asked google, and the first link I found where somebody had decided to attempt that operation had wound up with a face full of exploded battery, which did not encourage me to repeat the experiment. :D Tape will have to do the trick for now, hahaha!

      Many thanks again for all your advice - it's quite reassuring to know this is not an isolated case!

  4. Yes the battery was pre-tabbed: I got it from (I think! Pretty sure I get them there, if the guy is called Rob Webb or similar).

    Tried an untabbed battery once and, yep, it exploded. No harm done though.

    Let me know if you solve the mystery regarding the SRAM etc: my SNES Super Metroid is pretty useless at the moment, despite the new battery safely installed.

    And you're welcome for the advice: was reassuring for me too that other people had had similar difficulty with Super Metroid. Seems this only really happens with that game, from what I can gather.

    I should add that the game was saving fine before I changed the battery, but I wanted to put a new battery in to see how much such a cart would fetch on eBay, to see whether it was a viable enterprise. So.... changing the battery has caused something to happen which means the save wipes itself even with a good, new battery. I know the battery is installed properly because Samus doesn't die immediately like she does when there is no battery/the battery dies (there are youtube clips etc on that).

    Good luck!