Power failures are a fact of life, but if you are managing a data center or a corporate network, they can be catastrophic. Uninterruptable power supplies (UPS) help keep data centers humming even when there is a tripped breaker or larger outage.
UPS systems are typically built using lead-acid batteries to provide power in case of an outage, but these solutions have not evolved much in the past few years. Data centers increasingly are searching for ways to reduce the size and weight of these systems, reduce cooling requirements, and extend the life of UPS systems while reducing costs.
Lithium-ion (li-ion) batteries could address all of these needs. In fact, APC by Schneider Electric has already introduced li-ion batteries to its Back-UPS Pro line of UPS systems.
The key difference between a lithium-ion battery and a lead-acid battery is the mix of chemicals used in the electrodes and electrolyte within the battery. Lithium-ion batteries use a metal oxide for the cathode, and a carbon-based material for the anode. The electrolyte is a lithium salt dissolved in an organic solvent.
A lead-acid battery uses lead dioxide for the cathode, a lead anode, and sulfuric acid as the electrolyte.
Li-ion systems are relatively new to the UPS system space, but they can provide a number of key advantages for data center applications. These batteries generally have a higher specific energy/energy density than lead-acid batteries, a longer lifespan, a shorter recharge time, and are capable of completing a larger number of charge/discharge cycles (as many as two or three times more cycles than a lead-acid, depending on the chemical composition of the battery).
Below we’ve provided an analysis of some of the pros and cons of using li-ion batteries in UPS systems.
Total Cost of Ownership: For UPS systems, lithium-ion batteries are generally more expensive than lead-acid batteries, although those costs are falling. The real advantage for li-ion systems is in their lifespan. Over a 15-year period, lead-acid-based systems would need to be replaced two or three times, while li-ion systems may not need replacement at all.
That results in a lower cost of ownership (TCO) and lower maintenance costs. According to an analysis by Schneider Electric, li-ion-based UPS systems can have a TCO that is 10-40% less (as of 2016) than that of a lead-acid system over a 10-year period.
Safety: Li-ion batteries were once considered more volatile and prone to igniting fires than their lead-acid counterparts, but changes in cell packaging and chemistry have made them much safer. Li-ion batteries can also tolerate higher temperatures, which helps extend their lifecycle in data centers. Li-ion batteries also contain fewer hazardous substances than lead acid batteries, but are more difficult to recycle.
Re-Charge Speed: Charging either a li-ion or lead-acid battery to 80% takes roughly the same amount of time. But li-ion systems do have an advantage beyond that charge capacity. Reaching a 100% state of charge for lead acid batteries can take more than five to ten hours, while a li-ion battery can reach that state in 30 minutes to an hour.
However, li-ion systems are more sensitive to charging and discharging methods. Most of these batteries include a battery management system (BMS) to protect against short circuits and overcharging.
Space: This is where new battery technology can make a real difference for a data center. Li-ion batteries systems for a UPS can take up to 50% to 80% less floor space and weigh 60% to 80% less than a comparable lead-acid system. For data centers that are rapidly reaching floor and rack-space capacity, the shift to li-ion UPS systems could free up space, reduce clutter, and make it easier to reconfigure equipment.
UPS systems that use lithium-ion batteries instead of lead-acid can benefit data centers by reducing costs, saving space, and improving overall performance. There are a number of different li-ion chemistries available, and the chemical make-up of the battery can affect overall performance. Carefully evaluate the battery technology you utilize for your UPS systems before making an investment.