Jon Fingas, writing for Engadget: If Harvard researchers have their way, you may not have to worry about replacing power backs quite so often. They've developed a flow battery (that is, a battery that stores energy in liquid solutions) which should last for over a decade. The trick was to modify the molecules in the electrolytes, ferrocene and viologen, so that they're stable, water-soluble and resistant to degradation. When they're dissolved in neutral water, the resulting solution only loses 1 percent of its capacity every 1,000 cycles. It could be several years before you even notice a slight dropoff in performance. The use of water is also great news for both the environment and your bank account. As it's not corrosive or toxic, you don't have to worry about wrecking your home if the battery leaks -- you might just need a mop.