The Philips HeartStart Lithium Defibrillator Battery is a disposable, long-life battery designed for use with the Philips HeartStart HS1 and FRx defibrillators. This non-rechargeable battery is essential for ensuring the defibrillator is ready for use in an emergency. With a typical standby life of 4 years, keeping a spare battery on hand is advisable to ensure the defibrillator is always in working order.