On 4th July I bought a pack of 20 AA 1.5 volt batteries for a pound. I though 1.5 volt was 1.5 volt so they would be alright. But they don't work in my camera. I took them back to the shop and the lady said that they varied in strength and that these batteries would not work for the camera. I bought a packet of 4 Duracell batteries for £1.99. Will they be alright or do I need to buy even more expensive ones? They work at the moment, but how long will they last?