Hotline Electric Fencing Gemini Dual power energiser range are energisers that can be powered by either mains electricity or a 12v battery. The Gemini 40 is 0.8 stored joules energiser; the Gemini 80 has 1.2 stored joules and the Gemini 120 is a 2.4 joule energiser. They come with their own galvanised metal stand and have low battery indicators.