I did this a while ago but never posted about it and I have not seen a tutorial about replacing your battery without losing your save so I thought I would show what I did.

Some tools that you will need:
Your basic soldering tools
A USB cable that you do not mind cutting up
A power source for the USB cable, I used a wall adapted for cell phones
A new battery and SNES game
A security bit to open the game case

Start off by cutting off the end of your USB cable and strip the red and black wire, the red is positive voltage and the black is ground.

First check to make sure your game still has a working save file

Next open your game, here I am using Zelda

Here we can see the original battery

Then plug your USB cable into your power source and solder the USB cable to the capacitor on the 5 volt line, red wire to the positive leg and black wire to the negative leg

NOTE - As a componet heats up its resistance increases, wait about 1 minutes for the boad to cool down after connecting the wires to the capacitor


Now the board has power to be careful when working with it from here on out, be careful not to bridge the 5 volt line and the ground or else your save will be gone.

Next remove the old battery, to do this I heat one tab at a time and lift it out of the board then the other, if needed you can use some solder wick to remove any excess, again make sure you do not touch the positive and negative at the same time.

Now install the new battery and remove the USB cable from the board

Remember to let the board cool down before disconnecting the USB cable

Now put the game back together and put it back in the SNES and check your game save.

 

That's pretty cool! Thanks for the tutorial! I was wondering, would the 5v from a usb source like a PC or a Xbox be okay to use, or do you think it's better to use a cell phone wall adapter?

I am not sure how much amperage the chips take to power, a PC only outputs half an amp, I would use a wall charger because they normally have at least 1 amp output.

I think the SNES is rated for around 1 amp so a PC may or may not work because that 1 amp is running the console and game, for where I was working a wall adapter was a lot easier than a PC.

Also the Xbox would need to be turned on to power the port, to using a wall charger would consume less power than an Xbox.

Thanks, I'll bookmark this!

Awesome, thanks for the info. I thought as much since charging devices via a PC does take a bit longer than an adapter.

Wow, that's a really cool guide!

Very nice. Thanks for posting, OP! Do you think this or a similar method would be work on NES or Gameboy carts?

It should work for NES, GB/GBA, and Sega games. N64 games run off of 3.3 volts so you would need to use a low dropout voltage regulator. I think GBA might use 3.3 volts also not sure.

I did look at some of my GB carts and I could not find a good place to solder the wires to and I would not want to solder directly to the gold fingers. I did see someone on YouTube that started a GB game then swapped the battery while the game was running. That should work fine for a GB game because the PCB will not have any wiggle room unlike a SNES PCB.

Also GB carts the batteries are held in with surface mounted tabs so it should be a little faster to replace those than a SNES battery.

Could also just parallel another battery if you don't want to chop up a USB cable or deal with voltage regulators. Replace the board mounted one and then remove the one you just put in parallel.

Before I tried this I found a post where someone tried that with a Sega Genesis game but still lost the save. As a components heat up the resistance increases, that is also why I connected the USB cable to the capacitor.

Zelda was my second attempt, the first one I used Metroid and soldered the cable directly to the SRAM chip and it lost the save so then I tried soldering to the capacitor and it worked.


EDIT:just found it
http://freezerdev.blogspot.com/20...
Also added a few notes to let the board cool down after connecting the cable and before removing it,

That was one benefit of the old cart copiers.. to backup your SRAM (and keep it in a safe place) restoring after your cart no longer saves, but it's far cooler to MacGyver it like this.
Thanks for sharing!

Hrm, not sure what he did wrong. This is how I have always done it but your way is fine too. Additionally, can you edit your thread title to read "losing" instead of "loosing"? It's driving me nuts!

If you do this you can risk burning up the battery as it's only 3V and not meant to be charged. I use a lipo battery i have as it matches what you are putting in. Lest chance of heating the battery from a charge.

Good idea, but the execution seems like a disaster in the making.

The SNES runs off of 5 volts, all I am doing is giving power to the board while I replace the battery.  this is no more danger to the battery than playing the game on the SNES.

I think it would be easier just to plug the cartridge PCB into the console and change the battery while the game is running.

I've done something like this for my GameBoy games, not as good as this but worked. I opened the game and used a old GBA, started the game and played it a little and then as it was on.. I removed the battery and then replace the battery. Not the safest way of doing it but worked.

Could one not just solder a CR2032 holder on back side with wires and leave the old battery in place while having the new one as well and all be ok since it would be parallel and still getting the same 3V? I'm going to find out soon. I just replaced a zelda 2 one but took old one out but on a old copy of zelda I'm going to try what I mentioned & see if it keeps my old saves and keeps working.

Temporarily, while changing the battery, may be OK (I'm thinking under a minute or so).  But leaving it on there will have current flowing from the higher voltage battery into the lower one.  Basically charging a non-rechargable battery, not good.

The other issue is that attaching it requires heat which increases resistance. Too much resistance = loss of conductivity and the resulting SRAM data.  

A test clip for the SRAM chip would be pretty cool.   An old game copier would make quick work of it, as would a Retrode or something newer. I've heard of people using a Retron 5 to backup their saves as well. If the INL programmer/dumper had the right pin spacing I would try to turn it into a power source for inserted SNES carts. I have a dead SNES that I'll salvage the connector and 7805 from if I can't fix it and then I could make something tailor-made for powering the cart while swapping the battery.

I just posted a simpler way to do this, I mean really simple & no danger of damaging anything or losing a save. I felt it would be helpful so I just made another thread.

Good stuff! There's another way you can do this as well, without soldering. You can use a Super Wildcard DX for the SNES (cart dumper) and dump the SRAM right to a floppy. You can also transfer emulated SRAM files if you convert them using uCON64 with this same method. Of course, if you don't have one of those, this is the next best method.

I use a retron 5 to back up the save. Used to use a retrode but it was too unreliable for me, I couldn't always get the saves back on.