Ever since the UK Government introduce the feed-in-tariff (FIT) for solar PV and wind turbine installations, one of the biggest challenges has been how to store the generated energy for later use. Lead acid batteries have limited capabilities when it comes to frequent energy storage and discharge cycles and are more suited to standby power applications. Applications including electric vehicles and mobile computing applications also required an energy storage mechanism that could cope with rapid charge/recharge cycles and offer a longer working life. Lithium-ion batteries have rapidly become the energy storage device for these applications and are slowly being adopted into UPS system applications.