These are single use High Temperature galvanic primary cells also called Reserve Batteries .
They contain a metallic salt electrolyte which is non-conducting when solid at ambient temperature but which is an excellent ionic conductor when molten.
Activated by a pyrotechnic charge, they provide a high burst of power for a short period. (A few tens of seconds to 20 minutes or more)
They are rugged and safe with an indefinite shelf life in storage which makes them ideal for military applications.
Typical chemistry is Lithium Iron disulphide. The electrolyte is normally a eutectic mixture of lithium and potassium chlorides.
Power output ranges from a few watts to several kilowatts.
Able to withstand severe mechanical stresses of acceleration, shock, vibration and spin
High power and energy densities
Active chemicals are inert until activated
Long unactivated shelf life - Up to 20 years
Design can be optimised for power or capacity.
Operating temperature of 400 to 700°C must be maintained by the pyrotechnic charge throughout the duration of the application. Need insulation to conserve heat once activated.
Low temperature, low power devices using nano scale materials and semiconductor technology to convert thermal energy produced by the human body into electrical energy.
Resulting power can be used to trickle charge batteries for medium power devices or to drive low drain applications such as heart pacemakers.
Can be implanted.
Low energy conversion efficiency due to low operating temperature.
Use limited to low power applications.