roomba 694 battery dies super fast, like 20 minutes into a clean, and goes back to dock but the dock light is green.

Diagnosis

The iRobot Roomba 694 is experiencing a "voltage drop" failure. While the Home Base indicates a green light—signaling that the dock is powered and the robot has made contact—this does not mean the battery cells are actually holding a full charge. In these units, the nickel-metal hydride (NiMH) chemistry begins to degrade after 300-500 charge cycles. When the battery reaches a certain age, it develops high internal resistance; it can reach a "full" voltage quickly during charging, but as soon as the vacuum motors draw high current (especially when the brush rolls hit carpet), the voltage collapses, triggering the "Low Battery" return-to-home sequence prematurely. You can confirm this by observing the robot's behavior: if it dies significantly faster when cleaning high-pile carpets versus hard floors, it is a definitive sign of a failing battery cell. Another indicator is if the robot returns to the dock and immediately begins charging again despite only being away for 20 minutes. This confirms the battery can no longer maintain the required 14.4V threshold necessary to sustain the cleaning cycle.

How to Fix It

To resolve this, you must first eliminate "charging resistance" to ensure the battery is receiving maximum current, then perform a deep-cycle calibration.

1. Clean Charging Contacts: Power off the Roomba. Use a cotton swab dipped in 70% or 91% Isopropyl Alcohol to scrub the two gold-plated contact pads on the underside of the robot. Then, clean the two spring-loaded metal pins on the Home Base. If you see black carbon buildup or oxidation, use a standard pencil eraser to scrub the contacts until they are shiny.
2. Clear the Sensors: Wipe the cliff sensors (the windows on the bottom perimeter) with a dry microfiber cloth. Dust buildup here can cause the robot to "stutter," which consumes more battery power than a smooth glide.
3. Perform a Hard Reset: Press and hold the CLEAN button for 10 seconds. This clears the temporary cache and resets the battery gauge logic.
4. The 16-Hour Deep Charge: Place the robot on the dock manually. Ensure it is perfectly aligned. Leave the robot to charge for a full 16 hours without initiating any cleaning cycles. This allows the charger to perform a "trickle charge" to saturate the cells and recalibrate the internal battery meter.

If That Didn't Work

If the 20-minute death cycle persists after a deep charge, the hardware is failing and requires intervention:

• Replace the Battery Pack: The Roomba 694 uses the BACS02 battery model. To replace it, flip the robot over, remove the bottom cover screws using a Phillips #2 screwdriver, and lift the battery out of the compartment. Ensure the new battery is seated firmly; a loose connection here can cause intermittent power loss.
• Inspect the Main Brush Roll: Check for tangled hair or string around the ends of the yellow brush rolls. If the brushes are jammed, the motor works twice as hard to spin them, drawing excessive current and draining a healthy battery in a fraction of the usual time.
• Check for "Wheel Drag": Manually spin the two main drive wheels. If one feels stiffer than the other, a foreign object (like a pebble or hair clump) may be lodged in the axle, causing a mechanical drag that kills the battery prematurely.
• Update Firmware: Open the iRobot Home App and check for software updates. Occasionally, a bug in the power management firmware can cause the robot to misread the battery percentage, triggering an early return to the dock.

Heads Up

• Avoid Extreme Temperatures: Never charge your Roomba in a garage or area where temperatures drop below 50°F (10°C) or exceed 100°F (38°C), as this permanently damages the NiMH cell capacity.
• Dock Placement: Ensure the Home Base is on a hard floor surface. Placing the dock on a thick rug can cause the robot to struggle to dock properly, leading to "shallow charges" that degrade the battery over time.
• Storage Mode: If you plan to store the robot for more than two weeks, remove the battery entirely. Storing a degraded battery on a charger for months can lead to cell leakage or permanent failure.
• Genuine Parts: Only use certified BACS02 replacements. Cheap, generic batteries often have lower mAh ratings and lack the necessary thermal fuses, posing a fire risk during the high-current charging phase.