New energy storage technologies have been in research and development in the aim to accelerate the energy transition. Over the past 10 years, lithium-sulphur (Li-S) batteries, a technology that has a higher specific energy compared to lithium-ion (Li-ion) batteries have been in active research. Although Li-S batteries are seen as a promising alternative to Li-ion batteries, cell modelling and state estimation are non-trivial tasks due to Li-S's complex chemical reaction and non-monotonic characteristic between open circuit voltage and state of charge (SOC). This project aims to validate a novel method of using relative impedance difference for initial SOC estimation for an online application using power converters.