Lithium ion UPS Systems

Lithium UPS systems use lithium battery technology to provide backup power in the event of a mains power supply outage or interruption. A lithium-ion or (Li-ion) battery set is used in place of the standard lead acid battery type and the battery may be internal or supplied in a battery extension cabinet. UPS systems with high density lithium ion batteries are more compact than those with valve regulated lead acid batteries and can support faster and more numerous charge/discharge cycles. Lithium batteries are also more temperature tolerant than lead acid UPS batteries.

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The Advantages of Lithium-ion Uninterruptible Power Supplies

Lithium-ion batteries offer several advantages of lead acid batteries and the Valve Regulation Lead Avid (VRLA) batteries typically used within a UPS system. Due to the needs of lithium-ion for a more sophisticated battery management system, these advantages come with a price premium over a like-for-like sized lead acid battery-based UPS.

  • Less Temperature Sensitive: lithium-ion batteries can work up to 40°C without derating or limitation to their operating life; lead acid batteries must operation within 20-25°C
  • Rapid Cycling: lithium-ion batteries can be charged very quickly (up to 80% within 1hour) unlike lead acid batteries than can take up to 24hours to reach 80% charge capacity
  • Longer Operating Life: li-ion batteries can last 8-10 years and up to 1500 cycles before replacement is required; lead acid require replacement within 3-4 years for a 5 year design life battery and 7-8 years for a 10 year design at around 200-300 cycles
  • Improved Energy Efficiency: lithium-ion batteries are more than 96% efficient in both charge and discharge capacities

The lithium-ion batteries for UPS systems should be certified to IEC62133, UL1973 (Sec 5.7 & 5.8) and UN38.3. Aside from the cost of the batteries themselves, the UPS system using a lithium battery set must also have a more sophisticated battery management and charging circuit than the traditional types required for VRLA UPS batteries.

Lithium-ion UPS Battery Management

The battery management system must be able to monitor individual lithium-ion battery cells for temperature and voltage (for overtemperature and overvoltage conditions) which could lead to thermal runaway at the individual cell and battery pack level. The battery management system must be able to quickly detect any of these conditions and protect the battery pack and UPS installation with short-circuit protection to shut down the charging circuit.

Lithium-ion Batteries for Energy Storage Systems

The use of a higher cyclic battery set such as a lithium-ion one allows a UPS to perform as an energy storage system than a purely standby power backup one. Energy can be stored from off-peak rate electricity services and used to power the load during higher peak-charge periods, allowing the UPS to function as a virtual power plant to the connected loads.

This type of storage function also helps the UPS to assist national grids and demand side response (DSR) programmes. Here the UPS powers the load from its batteries to reduce demand on the grid and earns a fee from the grid operator.

Energy can also be stored from local renewable power plants including hydro, sola PV and wind turbine within the battery set for use by the UPS system to either protect the load or operate as a DSR generating system.

All these functionalities are suited to larger three phase uninterruptible power supplies due to their size (kW/kVA or MW/MVA) and the capital and operational costs involved.

For more information on lithium-ion UPS systems please contact our projects team.