the clock on my BDC455BSS resets to 1:00 every time i unplug it, even for a second. is the battery dead?

Diagnosis

The behavior you are describing—the clock reverting to the default 1:00 flashing display immediately after a power cycle—is a definitive symptom of a failed CMOS-style backup battery on the main control board. The Breville Precision Brewer Thermal BDC455BSS utilizes a small lithium coin cell to maintain the Real-Time Clock (RTC) and volatile memory settings (such as your preferred brew strength and temperature) when the machine is disconnected from AC power. When this battery reaches the end of its life cycle or drops below a specific voltage threshold (typically under 2.8V for a 3V cell), the circuit can no longer sustain the memory registers. Consequently, the microprocessor treats every plug-in event as a "first-time boot," wiping the internal clock and resetting the system to factory defaults. You can confirm this by setting the clock, unplugging the unit for just five seconds, and observing the immediate reset to 1:00; if the reset happens instantly, the battery is completely depleted.

How to Fix It

Replacing the battery requires accessing the internal electronics. Note that this is a hardware modification that involves the main PCB.

1. Safety First: Completely unplug the BDC455BSS from the wall outlet. Ensure the machine has cooled down completely if it was recently used.
2. Access the Base: Carefully lift the water reservoir and remove the thermal carafe. Flip the machine upside down onto a soft towel to avoid scratching the stainless steel finish.
3. Remove Baseplate: Locate the rubber feet on the bottom of the unit. Use a small flat-head screwdriver to pry these off. Remove the Phillips-head screws securing the plastic baseplate.
4. Expose the PCB: Gently lift the baseplate. You will see the main control board. Locate the CR2032 coin cell battery. In the BDC455BSS, this battery is typically soldered directly to the board rather than held in a clip.
5. Desolder the Old Battery: Using a soldering iron set to approximately 350°C (660°F) and a desoldering pump (solder sucker) or copper wick, remove the solder from the two contact points holding the battery in place.
6. Install New Battery: Insert a fresh, brand-name 3V CR2032 lithium battery, ensuring the polarity (+ side up) matches the markings on the PCB. Solder the battery leads firmly to the pads.
7. Reassemble: Replace the baseplate, tighten the screws, and re-apply the rubber feet. Plug the unit back in and set the clock one final time.

If That Didn't Work

• Check for Solder Bridges: If the clock still doesn't hold, reopen the base and inspect your solder joints. A "bridge" (a small blob of solder connecting the positive and negative terminals) will short the battery, causing the clock to reset. Use a solder sucker to clean the joints and retry.
• Test with a Multimeter: Use a digital multimeter to test the voltage of the new battery while it is seated on the board. If you read significantly less than 3V, you may have a defective battery or a parasitic draw on the board causing a rapid discharge.
• Inspect the RTC Crystal: If the battery is confirmed good but the clock drifts or resets, the quartz crystal oscillator near the battery may be damaged. This is a rare hardware failure and usually requires a professional board repair or a full PCB replacement.
• Verify Power Stability: If you are using a surge protector or a smart plug, try plugging the machine directly into a wall outlet. In rare cases, extreme voltage fluctuations during power-up can trigger a system reset that mimics a battery failure.

Heads Up

• Avoid Overheating: When soldering the CR2032, work quickly. Applying heat to the battery terminals for too long can damage the internal chemistry of the cell or lift the copper pads off the PCB.
• Static Discharge: Touch a grounded metal object before touching the internal circuit board to avoid electrostatic discharge (ESD), which can fry the sensitive microprocessor.
• Battery Quality: Avoid "no-name" or ultra-cheap coin cells. High-quality brands like Panasonic or Energizer provide a more stable voltage curve, which is critical for maintaining the RTC.
• Seal Integrity: Ensure the baseplate is screwed in tightly; a loose baseplate can cause vibrations during the brewing cycle that may eventually loosen the solder joints on your new battery.