I recently picked up this Neo Geo MV1FZ single slot board off eBay for a reasonable price (So many seem to be up there for £65+ and anything on an auction has a problem). simply because I have one working MVS board already but it’s got it’s original battery and MVS board batteries have a nasty habit of leaking and destroying the PCB leading to the dreaded “Calendar Error” message that I’ve had happen to a board of mine before.
It came, it was a little dusty but it worked. Nice. Now, my soldering skills are a bit suspect and I killed the last thing I tried to fix so this board was bought as an insurance policy in case I messed up again.
MV1-FZ
Taking off the cover of an MVS board is dead easy. 4 screws (3 in this case) and the plastic lifts off to reveal the PCB. Again. it’s a little dusty but actually in pretty good shape for a old PCB.
A Bit Dusty but pretty good!
Usually around the backup battery RAM area (where the battery lives) there is fur from where the acid has leaked from the button cell. Amazingly this wasn’t the case on this board! Looking at this and my existing MVS I think this one is actually in better shape so I thought I’d change the battery on this one and make it my main board.
Old battery area
The batteries on MVS boards look like Lithium Button Cell batteries but these are rechargeable. I have heard of people removing the originals and then cutting the recharge circuit to enable the replacement with a regular 3V battery that doesn’t recharge. I’m more of a purist so I don’t like to hack off bits of an original board for no reason and I do like to keep things as close to functional as possible.
With that in mind I found this little beauty! It’s made by Panasonic, has a sealant around the edge for safety and, crucially the legs are exactly the same distance apart as the holes on the motherboard so it’s a drop in replacement. Overall it’s a little smaller in size but I believe the capacity is roughly equivalent to the old, original battery.
The only place I found them is RS components. This is the link to the product. At this time they are a a reasonable £3.07 each. Cheap for another 20 years of battery backup on your MVS.
In case you wan to search elsewhere or that link breaks the description is “Panasonic 3V, VL2020 Lithium Vanadium Pentoxide Rechargeable Coin Cell Battery, PCB Pin Terminal, 20mAh”
New Rechargable Lithium Battery
To remove the existing cell from the PCB we must first deal with one of my most hated things…. STICKY BACK FOAM PADS! these things are horrible to remove as foam rips and gets stuck to the board. This time I’m going to be really, really careful.
Sticky Foam
And, even after 5 careful minutes of pulling, I still didn’t manage a clean job. However, the old battery terminals are now visible and clean enough that I can get to the solder points. I’m holding the pad back with Sellotape and I think there’s enough stick left to get the pad back down again once finished.
Taped Back Foam
To remove the battery is pretty simple. Take the soldering iron that’s warmed up and melt the solder on the two joints shown (one at a time). Have one hand on the battery so that when the solder melts you can pull the battery leg through the PCB. Doing this one at a time should make the job easy. Once the battery is out you can clean up the left over solder with solder wick or similar.
I didn’t take any pics of actually removing the old cell as I was concentrating too much on not breaking anything this time. However, above is with the old battery and below is with the new one. Attaching the new battery is as simple as placing the feet through the PCB and then soldering down. It’s a fairly big solder joint so is pretty easy to do. As you can see, the solder joint closest to the board edge is a bit poor but I’m happy enough with the other one.
Flipping the board over this is what the new battery looks like in place. Nice and secure and, if it turns on, ready for another few years of operation whilst being as close to stock as possible.
The new battery in place
Connecting the board up and turning it on reveals success! Games boot and settings can be changed. I left the system running for 20 minutes as the recharge rate on these batterys is really slow. turning it on later I still have my single high score and settings backed up.
Working after the surgery
I’m pretty sure this is my first 100% successful solder job. Even the foam pad whent back down again.
Protective foam pad
RetroGamingStuff 
This is just what I was looking for after realizing my board doesn’t hold much of a charge. Surprised to see this post is only a few months old! How’s it holding up? And did any research result in this seemingly obvious and straight forward battery replacement?
Thanks! The battery is holding up fine. Lasts blooming ages now after a few hours charge (multiple months for sure). This all came about from researching the “Callendar Error” issue i had on another board. Most common cause of this is the battery leaking and corroding the PCB. I didn’t want to get to this stage and wanted to keep the board “stock” so I found the battery and replaced it.
Just got myself a “new” MVS after my last one failed and the battery is a bit corroded. Not leaked yet. My delivery from RS arrived this morning and I am operating on her later. Let’s hope she pulls through. Thanks for the advice