Battery LEDs flash in a repeating pattern and the charger will not charge the battery; E6 or error light on charger.

Safety first: Do not attempt to open the battery pack. Damaged lithium-ion cells can be hazardous.

Steps to try:

• Check charger and outlet: Plug the Eureka charger into a different wall outlet. Confirm the charger's indicator light behaves normally without the battery connected.
• Inspect battery contacts: Look for dirt, corrosion, or bent contacts on the battery and charger. Clean gently with a dry cloth; do not use liquids.
• Reseat battery: Remove and reinsert the battery into the charger several times to ensure a solid connection.
• Observe LED pattern: If the charger immediately shows an error pattern (rapid flashing or red error LED) and never transitions to normal charging, the battery pack is likely defective.
• Test with another battery: If possible, charge a different Eureka battery on the same charger. If that battery charges normally, replace the faulty pack.
• Discontinue use: If the battery becomes swollen, emits odor, or gets hot while just sitting on the charger, unplug immediately and dispose of the battery according to local e-waste regulations.