Initially it seemed like a good idea getting an adapter, but besides the problem of the British weather being more wet than dry, there was the fact that the lead would not reach where I wanted it in my garden and the danger of electrocution. Through just using the square battery I have found that the repeller has kept cats out of my garden and the battery is still active more than 6 months after installing. The repeller has a test button to test how strong the battery is, just in case you wonder if it's still working. I regretted buying the adapter as I cannot see a purpose for it practically.