Only the first LED on the battery flashes repeatedly when on the charger; battery never progresses to higher LEDs.

Safety first: Use only the official Gtech charger. Do not attempt to open the battery pack.

Steps to try:

• Extended charging: Leave the battery on the charger for 8–10 hours even if only one LED flashes. Some packs recover slowly from deep discharge.
• Check charger output: If possible, test the charger with another compatible Gtech battery. If the other battery charges normally, the original pack is at fault.
• Inspect charger and contacts: Ensure the charger plug is fully inserted and the contacts are clean. Try a different mains outlet.
• Replace battery: If the pack never progresses beyond one flashing LED after extended charging, replace it with a genuine Gtech battery pack.