This Size D Lithium Thionyl Chloride battery is ideal for and widely used in utility metering, alarms and security devices, memory back-up, tracking Systems, SART and EPIRB devices and many others. Lithium Thionyl Chloride has the highest energy density of any practical Lithium battery chemistry, three times greater than Alkaline (Zinc Manganese Dioxide) batteries. It also has the widest operating temperature range of -55°C to + 85°C. Self discharge is low at less than 1% per annum at 20°C, giving an effective shelf life of 10 years.