A VRLA battery (valve-regulated lead-acid battery) is the designation for low-maintenance lead-acid rechargeable batteries. These batteries are often colloquially called sealed lead-acid batteries, but they always include a safety pressure relief valve. As opposed to vented (also called flooded) batteries, a VRLA cannot spill its electrolyte if it is inverted. Because AGM VRLA batteries use much less electrolyte (battery acid) than traditional lead-acid batteries, they are also occasionally referred to as an "acid-starved" design.