VMU battery
VMU and console clock batteries are coin cells. Never charge a non-rechargeable cell, never short its terminals, and dispose of old batteries properly. The console's own clock battery is rechargeable and must be handled accordingly, not swapped for a standard cell.
VMU and Clock Battery
Two small batteries keep time on a Dreamcast setup: the coin cell inside each VMU, and the rechargeable cell on the console mainboard that maintains the system clock. Both fail with age, producing the familiar clock-reset prompt at startup. repair
- Identify which battery. A VMU that beeps and shows a blank or wrong clock needs its coin cell; a console that forgets the time even with no VMU needs the mainboard cell.
- Open the VMU. Remove the rear cover and locate the coin-cell holder under the board.
- Swap the VMU cell. Replace it with a fresh coin cell of the same type, observing polarity. Saved game data survives because it lives in non-volatile memory.
- Service the console cell. The mainboard uses a rechargeable cell; if it no longer holds charge, replace it with the correct rechargeable type, never a standard one.
- Reset the clock. Power on and set the date and time to clear the prompt.
What you lose and keep
A dead battery only affects the clock and any time-based features. Your saved games remain intact on the VMU regardless of battery state.
Clock-dependent games
A few titles use the clock for in-game events. With a dead console cell you will have to set the time each session for those features to behave correctly.