SOURCE: Indrajit Majumdar / FOR MY TAKE / IDRW.ORG
DRDO has developed 250 KWs Silver Oxide Zinc (AgOZn), both primary and secondary batteries for propulsion of heavy weight torpedo Varunastra
DRDO’s Varunastra, the first indigenous heavy weight ship launched anti-submarine electric torpedo.It is capable of targeting quiet and stealthy submarines, both in deep and littoral waters in intense counter measure environment . The battery, which is used for heavyweight torpedo propulsion, will enhance the propulsion characteristics of the weapon. This will help in increasing the speed of torpedoes due to increased power from the present 100 kW to 250 kW, almost within the same space.
The current density required for a high-powered battery is of the order of 200 mA/cm2. This demands usage of a large amount of silver per ampere hour, a major part of which remains unrealised. To achieve the high battery voltage, a large number of cells need to be connected in series. These complexities often result into generation of high heat during discharging of the battery.
By the end of the discharge, internal heat generated in the cells leads to the situation where the electrolyte starts boiling. This results in spillage of electrolyte and resistance drop in battery. High temperature generated internally affects battery’s life cycle and its separators also. This requires working out of cell design, active material characterisation, and optimal use of separator material.
DRDO has developed a 250 kW secondary battery consisting of zinc as anode, silver oxide as cathode, and potassium hydroxide as electrolyte. lt delivers 400 V on load at a discharge current of 625 A for a short duration of 5 min.