Electrolux Pure i9.2 showing “Error E21: battery fault during use” has a specific manufacturer-backed troubleshooting path. The complete code E21 matters: a neighbouring number can require a different response. Confirm “Error E21: battery fault during use” exactly, including the full number, colour, flash order, spoken phrase or screen text. If any element differs, use the guide for that other indication instead. Electrolux — Pure i9 error table documents this condition for Electrolux Pure i9.2. It identifies the branch to test, but it does not by itself prove that a battery, motor, board, sensor, dock or replaceable part has failed. Stop the robot, remove it from the dock and confirm E21 in the app. Electrolux directs replacement of both batteries together; do not mix an old and new pack or substitute only the apparently weaker side. Power the robot off and remove it from the dock before turning it over or touching a moving part. Keep charging contacts dry and never open the battery pack or electronics housing. Run only one normal start, charge or cleaning cycle after the documented check. If “Error E21: battery fault during use” returns unchanged, record the code, model and serial number and contact authorised Electrolux support instead of repeating resets or guessing a part.
Models covered
Safety first
- Power the robot off and remove it from the dock before turning it over or touching a moving part. Keep charging contacts dry and never open the battery pack or electronics housing.
What the symptom may indicate
Checks in the right order
- Identify the exact indication
Confirm “Error E21: battery fault during use” exactly, including the full number, colour, flash order, spoken phrase or screen text. If any element differs, use the guide for that other indication instead.
- Safe check to perform
Stop the robot, remove it from the dock and confirm E21 in the app. Electrolux directs replacement of both batteries together; do not mix an old and new pack or substitute only the apparently weaker side.
- What to do after the test
Run only one normal start, charge or cleaning cycle after the documented check. If “Error E21: battery fault during use” returns unchanged, record the code, model and serial number and contact authorised Electrolux support instead of repeating resets or guessing a part.
Stop and get qualified help when
- Stop for liquid on the robot or dock, a swollen battery, burning smell, hot or discoloured contacts, damaged wiring or the same alert after the single documented check. Run only one normal start, charge or cleaning cycle after the documented check. If “Error E21: battery fault during use” returns unchanged, record the code, model and serial number and contact authorised Electrolux support instead of repeating resets or guessing a part.
Next step
Repair, replace a part, or arrange a diagnosis?
Use the checks and stop conditions above to choose a cautious next step. A symptom alone never proves that the appliance has failed.
Resolve it without buying anything
Complete the 3 user-accessible checks in order. If normal operation returns and no warning sign remains, no replacement is indicated.
Replace only the confirmed part
If the checks isolate a worn or blocked component, match its complete reference to the exact appliance model before ordering.
This guide does not identify a replacement part. Do not order a generic component from the symptom alone.
Arrange a diagnosis before replacing the appliance
Stop at any warning sign listed above. A qualified diagnosis should confirm that repair is unsafe, unavailable or uneconomical before an appliance replacement is considered.
Sources used
- Electrolux — Electrolux, Pure i9 error table: “E:21 - Les batteries présentent un dysfonctionnement en cours d'utilisation. Changez les 2 batteries.” This exact manufacturer wording anchors the check for Electrolux Pure i9.2.
Last checked: 30 August 2026