my roborock s7 is stuck on 'charging' but the battery never goes above like 20%, it just sits there forever.

Diagnosis

This behavior is typically indicative of a "false positive" charging state, where the Roborock S7's Battery Management System (BMS) detects voltage at the charging pins but cannot successfully bridge the current into the lithium-ion cells. When the battery hangs at a specific percentage (commonly between 15% and 25%), it usually means the BMS has entered a protection mode or the battery cells have drifted too far apart in voltage, preventing the charger from pushing the battery to 100% to avoid overheating or cell rupture. Another common cause is oxidation or microscopic debris on the charging contact plates. Even if the plates look clean, a thin layer of non-conductive residue can create enough resistance that the robot registers a connection (triggering the "charging" status) but cannot draw the high amperage required to actually increase the state of charge. To confirm this, check if the robot remains on the dock but the charging light pulses or flickers intermittently rather than staying solid.

How to Fix It

To resolve this communication glitch and restore the charging cycle, follow these precise steps:

1. Remove the robot from the dock and flip it over to ensure no debris is lodged in the charging contact points on the underside.
2. Perform a deep power cycle: Locate the power button on the top/side of the unit. Press and hold it firmly for 20 seconds. You should hear a shutdown chime, and the LED indicators must go completely dark.
3. Clean the charging contacts: Use a cotton swab dipped in 70% or 91% Isopropyl alcohol. Scrub the two gold-plated contact pads on the bottom of the S7 and the two spring-loaded pins on the Roborock dock. Wipe them dry with a lint-free cloth to remove any residue.
4. Reset the dock: Unplug the charging dock from the wall outlet for 60 seconds to discharge the internal capacitors, then plug it back in.
5. Manual Docking: Instead of letting the robot navigate back, manually push the S7 onto the dock, ensuring it is perfectly centered and flush against the backplate.
6. Leave the unit undisturbed for 4 hours. Do not start a cleaning cycle or trigger a "Spot Clean" until the app confirms 100% charge.

If That Didn't Work

• Calibrate the Battery: If the percentage is stuck due to a software miscalculation, force a full discharge. Run the robot on "Max" suction mode in a large area until it completely dies and shuts itself off. Once dead, manually place it on the dock and let it charge to 100% without interruption. This resets the BMS voltage floor and ceiling.
• Inspect for Pin Compression: Check the spring-loaded pins on the charging dock. Use a small toothpick to gently press them down; they should spring back instantly. If one pin is stuck in the "down" position, the robot will show it is charging but will only receive a trickle charge, preventing it from ever reaching full capacity.
• Firmware Forced Update: Open the Roborock app and check for a firmware update. If one is available, install it while the robot is on the dock. If it is already up to date, try "Resetting" the device within the app settings to clear the cached mapping and power data.
• Battery Replacement: If the unit is over 2 years old and the percentage remains frozen after a deep discharge/charge cycle, the internal 5200mAh battery pack has likely developed a dead cell. You will need to replace the battery pack (Part No: Roborock S7 Battery) by removing the bottom plate and disconnecting the battery harness.

Heads Up

• Avoid using abrasive scouring pads on the gold charging contacts, as scratching the plating increases electrical resistance and can lead to overheating.
• Ensure the dock is placed on a flat, hard surface. If the dock is on a thick rug, it can tilt slightly, causing the charging pins to make poor contact and leading to the "stuck percentage" issue.
• Do not leave the robot on the dock for more than two weeks without use; this can cause the battery to enter a "deep discharge" state that is often irreversible.
• Keep the charging area free of dust buildup; vacuum the dock's base regularly to prevent debris from pushing the charging pins out of alignment.