It's risky business no matter what you do, there's always a small chance of losing the save file. The battery circuits on the NES carts weren't perfect to begin with, so that doesn't help either.
Since the SRAM usually wont lose the save the second you remove power, it's usually possible to change the battery and still have your saves if you're able to do it fast enough. Of course, like I said, there's still a chance of losing the save, so I wouldn't recommend this as the number one choice.
I've heard the suggestion to replace the battery while the cart is powered on in the console. Yes, the SRAM would never lose power in this case, but that's risky business. I really wouldn't recommend doing it. Especially with an NES because of the design of the console, it'd be really hard or even impossible. I don't recommend trying this method at all.
But that gave me an idea, although I haven't tried it yet. The short of it is to wire in another battery in parallel before you remove the old battery, that way the SRAM never loses power.
Wiring two batteries in parallel will keep the voltage same. Solder two wires to alternative points for the battery's positive and negative connections. Connect a temp battery to those wires. Swap the old battery out for a new one. Remove the temp battery. The SRAM will have never lost battery power. In theory, this should work perfectly every time. Unless I'm overlooking something, like the mA increasing, but I'm sure the console provides more amps to the SRAM than the battery anyways. It'd probably be best to remove the old battery ASAP after installing the second battery just to be safe, but I don't think the two batteries would harm anything.
Alternatively, a lot of people wire in a battery holder instead of buying a new battery with the solder tabs already welded on. So if that's the case, you could just wire the battery holder in parallel, install the new battery into the holder, then remove the old battery. You would save a step by not needing a temp battery.
But seriously, you should check the voltage of the battery that's in there now before even worrying about changing it. You just need a security bit and a multimeter, if you don't already own them. If the voltage is 3v or higher you'll be fine until the CopyNES comes back in stock. Hell, even if the voltage is slightly below 3v you'd probably still be OK, but that's cutting it too close. But yeah, if the voltage is strong, then there's no need to change it yet and risk losing the save.
Possible to back up NES save data?
Re: Possible to back up NES save data?
Hah - that's an awesome method, Ziggy! It's so obvious, but I've never heard of anyone doing it that way before. I'm going to do be doing that to my carts when I get home. Thanks!
Re: Possible to back up NES save data?
I KNOW! It seems so simple... why hasn't this been established yet? Is it because I'm a genius and no one thought of it, or is it because doing it this way will cause a nuclear reaction? 
edit: Well I couldn't let you do it before me, since it was my idea...
It works!
I take no responsibility if you try this and damage something. Attempt at your own risk. Only attempt if you KNOW what you're doing!
That's actually my Zelda NES cart. The battery that was in there measured 3.301v. The new battery that I put in was also 3.3v. So right there that tells me that having two batteries with nearly 100% juice wont damage anything. At least, if you do it quick enough. The old battery was removed no longer than 30 seconds after the new battery was installed. But you could probably leave it with two batteries connected indefinitely without a problem.
Like I said, I soldered to alternative points for the battery positive and negative connections. Negative is easy, it's just ground, so you can solder to any ground on the cart. The positive went straight to the leg of a diode, so that's where I soldered the other wire to. I don't know if it makes a difference, but with the second battery, I soldered negative first and then positive.
As soon as I connected the positive wire of the new battery I immediately removed the old battery. Loaded the cart up and the save was still there!
I wasn't gonna leave it like that, I wanted to put the old battery back in (since it was actually rather new). As a test, before putting the old battery back in, I disconnected the new battery for maybe 10 or 15 seconds then reconnected it. Checked it again and my save was gone. You can't swap a battery in 15 seconds, so I wouldn't recommend doing that if you wanna try and change the battery without losing your save. Like I said before, some times if you swap the battery quick enough your save will still be there. But that's not a sure fire thing. In this case, leaving the battery off for a mere 15 seconds was enough to lose the save.
@ kotetamer: I said it before, but I'll say it again. Before worrying about changing the battery you should first check the voltage of the one that's in there. You might not have to worry about changing it right away if it's strong enough.
About the security bits, my Zelda cart had the screws that can be opened with a small flat head screwdriver (older NES carts had these instead of security bits). I bet there's newer Zelda carts with security bits, but I guess mine was old enough to have the kind that you can open with a flat head. So check yours, you might not even need the security bit to open it. You'll still need the voltage meter to check the battery though, of course.
Speaking about carts produced later than others, it is possible that the PCB was revised in a later production. I don't think it was, but it is possible. Don't use my pic as a guide if you choose to do this, confirm where the negative and positive connections should go before connecting them. Connecting them to the wrong locations could cause damage, and definitely not power the SRAM so you'd lose your save.
And to reiterate, having a strong or fresh battery doesn't guarantee your save will hold. If you really value a save file, backing it up (with the CopyNES in this situation) is your best bet. That way, if the save ever drops you can always restore it. And also remember to hold reset while powering of the NES. Push and hold reset, push the power button, then release rest. This prevents the console from corrupting the SRAM.
edit: Well I couldn't let you do it before me, since it was my idea...
It works!
I take no responsibility if you try this and damage something. Attempt at your own risk. Only attempt if you KNOW what you're doing!
That's actually my Zelda NES cart. The battery that was in there measured 3.301v. The new battery that I put in was also 3.3v. So right there that tells me that having two batteries with nearly 100% juice wont damage anything. At least, if you do it quick enough. The old battery was removed no longer than 30 seconds after the new battery was installed. But you could probably leave it with two batteries connected indefinitely without a problem.
Like I said, I soldered to alternative points for the battery positive and negative connections. Negative is easy, it's just ground, so you can solder to any ground on the cart. The positive went straight to the leg of a diode, so that's where I soldered the other wire to. I don't know if it makes a difference, but with the second battery, I soldered negative first and then positive.
As soon as I connected the positive wire of the new battery I immediately removed the old battery. Loaded the cart up and the save was still there!
I wasn't gonna leave it like that, I wanted to put the old battery back in (since it was actually rather new). As a test, before putting the old battery back in, I disconnected the new battery for maybe 10 or 15 seconds then reconnected it. Checked it again and my save was gone. You can't swap a battery in 15 seconds, so I wouldn't recommend doing that if you wanna try and change the battery without losing your save. Like I said before, some times if you swap the battery quick enough your save will still be there. But that's not a sure fire thing. In this case, leaving the battery off for a mere 15 seconds was enough to lose the save.
@ kotetamer: I said it before, but I'll say it again. Before worrying about changing the battery you should first check the voltage of the one that's in there. You might not have to worry about changing it right away if it's strong enough.
About the security bits, my Zelda cart had the screws that can be opened with a small flat head screwdriver (older NES carts had these instead of security bits). I bet there's newer Zelda carts with security bits, but I guess mine was old enough to have the kind that you can open with a flat head. So check yours, you might not even need the security bit to open it. You'll still need the voltage meter to check the battery though, of course.
Speaking about carts produced later than others, it is possible that the PCB was revised in a later production. I don't think it was, but it is possible. Don't use my pic as a guide if you choose to do this, confirm where the negative and positive connections should go before connecting them. Connecting them to the wrong locations could cause damage, and definitely not power the SRAM so you'd lose your save.
And to reiterate, having a strong or fresh battery doesn't guarantee your save will hold. If you really value a save file, backing it up (with the CopyNES in this situation) is your best bet. That way, if the save ever drops you can always restore it. And also remember to hold reset while powering of the NES. Push and hold reset, push the power button, then release rest. This prevents the console from corrupting the SRAM.
Re: Possible to back up NES save data?
Mine does require the security bit, I'll have to get the voltage meter to check the battery. It's amazing that you managed to pull this off, honestly a fantastic work of soldering!
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fastbilly1
- Site Admin
- Posts: 13775
- Joined: Tue Apr 17, 2007 7:08 pm
Re: Possible to back up NES save data?
Ziggy, you continue to astound me.
Re: Possible to back up NES save data?
So I haven't gotten to touch Zelda yet, I've been insanely busy with work and other things but I did have a friend point out a very interesting website.
http://www.timewalkgames.com
They say they'll back up your old save data and fix your cart to like new for only about $10. This seems like a fantastic service, has anyone used them before?
http://www.timewalkgames.com
They say they'll back up your old save data and fix your cart to like new for only about $10. This seems like a fantastic service, has anyone used them before?
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chuckergreg
- Newbie
- Posts: 1
- Joined: Mon Aug 24, 2015 4:35 pm
Re: Possible to back up NES save data?
For anyone who stumbles across this in the future, and is curious, there is no risk in "too much current" for the SRAM chip - just don't exceed the voltage (~3.3v). Honestly, I plan to parallel several batteries to provide a much longer retention life than the single CR2032 these cartridges usually use.
The reason there is no risk, is because the battery determines only the voltage, it's the SRAM chip that determines the current. Additional batteries would ALLOW the SRAM to use more current IF it was trying to - but it isn't trying to. We know this because the existing battery lasts years - not hours. i.e. The SRAM chip is using far, far less current than even the existing battery can provide.
Greg
The reason there is no risk, is because the battery determines only the voltage, it's the SRAM chip that determines the current. Additional batteries would ALLOW the SRAM to use more current IF it was trying to - but it isn't trying to. We know this because the existing battery lasts years - not hours. i.e. The SRAM chip is using far, far less current than even the existing battery can provide.
Greg
Re: Possible to back up NES save data?
Not a cheap solution, but if you had a Retron 5 you could dump the raw save data to the system upon the first time it boots up the game and keeps it there. You then just remove the game, swap the battery, place it back in the system, then on the R5 just do 'copy data to cart' and you're done.
Re: Possible to back up NES save data?
Hey, thanks for the info! I thought that was the case, but I'm no electrical theory expert so I didn't know for sure. Thanks for confirming!chuckergreg wrote:For anyone who stumbles across this in the future, and is curious, there is no risk in "too much current" for the SRAM chip - just don't exceed the voltage (~3.3v). Honestly, I plan to parallel several batteries to provide a much longer retention life than the single CR2032 these cartridges usually use.
The reason there is no risk, is because the battery determines only the voltage, it's the SRAM chip that determines the current. Additional batteries would ALLOW the SRAM to use more current IF it was trying to - but it isn't trying to. We know this because the existing battery lasts years - not hours. i.e. The SRAM chip is using far, far less current than even the existing battery can provide.
Greg
Re: Possible to back up NES save data?
"Replace Your Game Cart Batteries (Without Losing Your Saves)!"
