Charger LED flashes a specific pattern and the vacuum battery will not charge; charger or manual indicates F1.

Safety first: Unplug the charger from the wall before inspecting.

• Verify compatibility: Confirm that the battery model number matches the charger and vacuum specifications. Do not attempt to charge third‑party or modified packs.
• Inspect contacts: Check the charger and battery terminals for dirt or corrosion. Clean gently with a dry cloth.
• Try another outlet: Plug the charger into a different wall outlet to rule out supply issues.
• Test with another battery: If another compatible Hitachi battery charges normally, the original battery’s ID circuit is likely faulty and the pack should be replaced.

If F1 occurs with multiple batteries, the charger itself is likely defective and should be replaced with an original Hitachi charger.