SOLAR POWERED - SELF RECHARGE | These auto darkening welding lenses have built in batteries, and solar panels. The solar panels recharge the lens, so you never need to worry about batteries again. Note that the solar panels don't charge in the sun, but charge just by welding. Your weld arc recharges the auto welding lens, so you never need to manually recharge the lens either. The batteries eventually die, but they are cheap and easy to find. They are CR1025 batteries