If you have energy-saving solar-powered outdoor lights in your garden that don't illuminate as long as they used to, it may be time to check the batteries. Solar-powered lights use rechargeable batteries that charge during the day, using the sun's light as an energy source. The lights then switch on their integrated LED bulbs at night, using the batteries' charge. Over time, the batteries lose their ability to charge and need to be replaced. Replace those batteries with new rechargeable batteries every two years, and you'll see your lights working almost as good as new.