How to Replace Save Batteries in Famicom Disk System Games

Quick answer

To replace a dead save battery in a Famicom Disk System game, open the disk card, desolder the old battery, install a fresh CR2032 or equivalent with a solder tab, and verify the save. Work on a static-free surface and use a temperature-controlled iron. This guide walks you through each step with checkpoints to avoid common mistakes.

Tools and parts you'll need

Before you start, gather a Phillips #00 screwdriver, a temperature-controlled soldering iron with a fine tip, desoldering braid or a solder sucker, 60/40 or lead-free solder, flux, isopropyl alcohol, and a new battery. The FDS typically uses a CR2032 coin cell with solder tabs, but check your specific game's battery orientation and size. A multimeter helps confirm voltage before and after.

Work on a clean, well-lit surface. Use an anti-static wrist strap or regularly touch a grounded metal object to discharge static. Avoid working on carpet.

Opening the disk card

Remove the game from its sleeve and locate the small screw on the back of the disk card. Unscrew it and gently separate the plastic shell. Be careful not to force it; some cards may have clips. Once open, you'll see the battery holder or soldered battery on the board.

Take a photo of the battery orientation before removal. Note which side is positive (usually marked with a plus sign on the board).

Removing the old battery

If the battery is soldered, apply flux to the joints and use desoldering braid or a solder sucker to remove the solder. Gently pry the battery up once the solder is removed. If it's in a holder, simply lift it out. Avoid pulling on the battery tabs, as this can damage the pads.

Clean the area with isopropyl alcohol and a cotton swab to remove flux residue.

Installing the new battery

Insert the new battery with the correct polarity. If soldering, tin the pads and the battery tabs first, then solder the tabs in place. Use minimal heat to avoid damaging the board or the battery. If using a holder, simply snap the battery in.

Double-check polarity before soldering. Reversing polarity can destroy the save circuit.

Testing and reassembly

Use a multimeter to check the voltage across the battery terminals; it should read around 3V. Reassemble the disk card and screw it back together. Insert the game into your Famicom Disk System and test a save. If the game saves and loads correctly, the replacement was successful.

If the game doesn't save, recheck the solder joints and battery orientation. Some games may require a specific battery type; consult the game's manual if available.

Step-by-step battery replacement

1. Prepare your workspace: Clear a static-free area, gather tools, and wear an anti-static strap. Common mistake: working on carpet, which can cause static damage. Checkpoint: Ensure all tools are within reach and your iron is at the correct temperature (around 350°C for leaded solder).
2. Open the disk card: Remove the screw and gently separate the shell. Common mistake: forcing the shell and cracking the plastic. Checkpoint: Take a photo of the battery orientation before proceeding.
3. Desolder the old battery: Apply flux and use desoldering braid to remove solder from the tabs. Common mistake: overheating the board, which can lift pads. Checkpoint: Clean the area with isopropyl alcohol after removal.
4. Install the new battery: Place the new battery with correct polarity and solder it in place. Common mistake: reversing polarity, which can damage the save circuit. Checkpoint: Verify voltage with a multimeter (should be ~3V).
5. Reassemble and test: Screw the card back together and test a save in your FDS. Common mistake: not testing before fully reassembling. Checkpoint: If the save works, you're done. If not, recheck solder joints and battery orientation.

Product facts

• Dreamcast Express Vol 3: Second hand. Card case. Two disks. This Dreamcast Express Vol 3 is a second-hand item with a card case and two disks, so if you're buying it for its save feature, note that Dreamcast games typically use VMU saves, not batteries. However, the card case can be repurposed for storing small parts during your FDS battery replacement project.