The FAA has issued Special Conditions for the Cessna 680 Sovereign, for which Cessna proposes to use rechargeable lithium-ion main batteries and APU start batteries. According to the FAA, lithium-ion batteries differ significantly from the nickel-cadmium (Ni-Cad) and lead-acid rechargeable batteries currently approved. The FAA determined that existing regulations do not adequately address several failure, operational and maintenance characteristics that could affect the safety and reliability of rechargeable lithium-battery installations. Therefore, the agency is requiring that all characteristics of the lithium batteries and their installation that could affect safe operation of the Cessna Sovereign are addressed; and that appropriate instructions for continued airworthiness, which include maintenance requirements, are established to ensure the availability of electrical power from the batteries when needed. “Cessna is working on this as a feature for future Sovereigns but it’s more of a long-term project rather than anything near term. It’s been the standard battery on the CJ4 since we introduced the aircraft in 2010. We do have a Ni-Cad option for the CJ4, but we’ve found that most customers prefer the lithium version,” a spokesman for Cessna told AIN.