roomba i3+ evo won't charge on the home base, the light ring is red and pulsing. i've tried repositioning it.

Diagnosis

The pulsing red light ring on the iRobot Roomba i3+ EVO indicates a critical power failure or a charging fault. While this can sometimes signal a battery failure, it most frequently occurs when the robot cannot establish a stable electrical connection with the Clean Base. This is typically caused by "contact oxidation" or the buildup of microscopic debris, dust, and pet hair on the metallic charging plates. Even a thin layer of grime can create enough electrical resistance to prevent the charging circuit from closing, triggering the red alert. To confirm this is a contact issue rather than a dead battery, observe the robot as it docks. If the robot physically touches the base but the light ring remains pulsing red without switching to a white "charging" indicator, the physical connection is failing. If the robot fails to dock entirely or "hunts" for the base without ever making contact, the issue may be related to the IR sensors or the base's positioning, but the red pulsing light specifically points to a power delivery failure once docked.

How to Fix It

Follow these precise steps to restore the electrical connection between the i3+ EVO and its Clean Base:

1. Power down the robot by pressing and holding the CLEAN button for 10 seconds until the light ring turns off completely.
2. Flip the robot over and locate the two large circular metallic charging contacts on the underside. Use a dry, lint-free microfiber cloth to wipe them. If there is visible discoloration or "pitting," use a melamine foam sponge (Magic Eraser) dampened slightly with distilled water to scrub the contacts until they are shiny. Dry them immediately.
3. Inspect the Clean Base. Locate the two spring-loaded charging pins. Ensure neither pin is stuck in a recessed position; they should spring back up when pressed.
4. Clean the base contacts using a cotton swab dipped in 70% isopropyl alcohol. Gently scrub the surface of the pins to remove carbon buildup or oxidation.
5. Ensure the Clean Base is on a hard, level surface. If the base is on a thick rug, it can tilt slightly, causing the robot to dock at an angle that prevents the pins from making full contact. Move the base to a hard floor for testing.
6. Place the robot manually onto the base, ensuring it is pushed firmly against the charging pins. Wait 30 seconds to see if the light ring changes from pulsing red to solid white.

If That Didn't Work

• Perform a Hard Reset: Sometimes the i3+ EVO's onboard computer hangs in an error state. Press and hold the CLEAN button for 20 seconds. The light ring will flash; release the button and allow the robot to reboot completely before attempting to dock it again.
• Inspect the Power Cord Seat: Check the power cable where it enters the Clean Base. Ensure the plug is pushed fully into the socket. A loose connection here can provide enough power for the base's LEDs but not enough amperage to charge the battery, resulting in the pulsing red light.
• Battery Reseating: If the robot has been stored for a long period, the battery may have dropped below the minimum voltage threshold. Remove the three screws on the bottom panel to access the battery. Disconnect the battery cable, wait 30 seconds, and reconnect it. This can sometimes "wake up" the battery management system.
• Test the Outlet: Plug the Clean Base into a different AC outlet on a separate circuit. Avoid using surge protectors or extension cords, as these can occasionally cause voltage drops that interfere with the i3+ EVO's sensitive charging circuit.

Heads Up

• Avoid using abrasive steel wool or heavy chemicals on the charging contacts, as this can strip the plating and lead to permanent corrosion.
• Periodically check the bottom of the robot for "hair wraps" around the side brushes; if the brushes are too clogged, the robot may dock at a slight angle, preventing the charging contacts from aligning perfectly.
• Never use a third-party power adapter. The i3+ EVO requires the specific voltage and amperage provided by the official iRobot power supply to avoid frying the motherboard.
• If the pulsing red light persists after cleaning and resetting, the internal Lithium-ion battery may have reached the end of its life cycle and will require a full replacement.