The power system used in VARUN is a simple compilation of lithium polymer batteries and dc-dc converters to get different voltages required to drive various systems. Protective circuits to prevent back emf generated in the thrusters have been incorporated in the 2nd generation vehicle.

Lithium Polymer Batteries

The Li-Po battery differentiates itself from other battery systems in the type of electrolyte used.  It resembles a plastic like film that does not conduct electricity but allows exchange of ions. It is light, low on volume, has a high energy density and requires minimal maintenance. The requirements have been met by using custom made batteries, using three at a time.

The Drive system

Two 14.8V, 9.6Ah Li-Po batteries are used in the drive system to power the thrusters, which have electrical rating of 28 ± 10%, 4.5 amps. From the thrusters specification, it has been found that the thrusters when in forward motion require 2.45 amperes of current, and in the backward motion requires 2.42 amperes when a potential difference of 14.8V is applied. The maximum run time in this case with full power delivered by the battery would be 49 minutes.

The Embedded Systems

To drive the embedded components and IC’s another battery of 14.8V, 8Ah is used. The embedded systems and drive system are not driven by a single battery to minimise electromagnetic interference between the two supplies to their respective loads, to near zero. This calls for the need of appropriate insulation to shield them from each other.

DC-DC Converters

To deliver the power to each of the components at a single stable voltage, Astrodyne voltage converters have been used. They have been decided on the basis of the voltage and power requirement of the individual components. ASD20-1285 converters have been used for the purpose.