not bigger Increased miniaturisation of appliances drives technological advance, as manufacturers can't simply make batteries bigger. "There's only so much space for batteries inside an appliance," says Duracell's Suren Raymond. "So you have to improve the chemistry within the cell by using more activeingredients. You can also modify the manufacturing process ­ a thinner outer casing means more room for the ingredients and more power." {{FOCUS SPECIALS }}