UPS

Key reasons why  Li-Ion batteries make  sense in UPS designs

SIZE AND WEIGHT MATTER 

 Compared to VRLA batteries, Li-Ion batteries are much smaller and lighter. Li-ion  batteries, on average, weigh 60-75% less and take up only 40-50% of the size  

(footprint) of equivalent VRLA batteries. Another way to look at this is for the same  amount of battery capacity (Wh), Li-Ion batteries take up roughly half the space  of their VRLA equivalent. 

Taking ventilation requirements and/or the need for VRLA batteries to be located in  a separate room into account, the footprint required for Li-Ion batteries and thecost associated with that space, reduce even further.  

Less size and weight can also contribute to savings in shipping, handling, and deployment costs. When a Li-Ion UPS is used in an In-Rack or In-Cabinetpower architecture, it may consume 2U to 3U of rack space, while a VRLA UPS of the same capacity would consume 5U to 8U of rack space. Using the Li-ion UPS would allow the user to “reclaim” 3U to 5U of space, which can be dedicated to  revenue-producing IT equipment.  

LONGER LIFE AND LOWER TCO

Li-Ion batteries have a longer life than VRLA batteries. On average, the lifespan for VRLA batteries is three  to five (3 to 5) years, while Li-Ion batteries have an  average lifespan of seven to ten (7 to 10) years. This  equates to, on average, two (2) service maintenance  schedules to replace VRLA batteries over a UPS  product’s lifespan. Using Li-Ion batteries in that same  UPS application virtually eliminates the need for  battery replacements. 

The initial capital outlay for a Li-Ion UPS solution is  roughly 1.75-2x the cost of the same capacity VRLA  solution. However, once you factor in the costs of  replacing lead-acid batteries every 3-5 years (and  include the labor, shipping, travel costs associated with  battery replacements), the Total Cost of Ownership  (TCO) starts to favor the Li-Ion UPS over the life of the UPS deployment. This can be particularly relevant  when the UPS is located in remote locations or remote  data centers.  

HIGHER AMBIENT TEMPERATURE  TOLERANCE 

There are a number of environmental conditions  that can further reduce the life of VRLA batteries but  operating in higher ambient temperatures is a major  contributor. VRLA batteries work best at room temp  25°C (77°F), and for every 8.3°C (15°F) increase in  temperature above room temperature, the life of the battery can be reduced by as much as 50%. Li-Ion  batteries can operate at ambient temperatures up  to 40°C (104°F) with little to no impact on battery performance or life. 

THE EFFECTS OF CHARGING AND  DISCHARGING ON BATTERIES 

Charging, discharging, and the effect it has can vary  greatly when comparing Li-Ion batteries to VRLA batteries. VRLA batteries start losing capacity from  the very first charge/recharge cycle and continue to  lose capacity with every charge and discharge cycle  thereafter. VRLA batteries reach their “end of useful life,”which in a UPS is generally defined as when the batteries hit 80% of their rated capacity in  ampere-hours, much more quickly than Li-Ion  batteries. Li-Ion batteries have a higher cycle life for a given depth of discharge, and depending on the chemistry, they can withstand more than 2000 charge  and discharge cycles with minimal impact on capacity. 

BATTERY FLEXIBILITY 

The superior cycle performance of Li-Ion batteries  also makes them more versatile than VRLA batteries.  Li-Ion UPS’ can be designed to use the battery pack  

to supplement the AC grid, in addition to using them for the ‘normal’ back-up power source during  power outages. Using the Li-Ion batteries to supply  

supplemental power is referred to as Peak Shaving (or Peak Boost). This allows the UPS to set a power  threshold ‘cap’ that it draws from the AC grid,  allowing the Li-Ion batteries to provide additional or supplemental power consumed by the IT load. 

Please see the Enconnex Peak Shave Application Note and/or our blog “How Peak Shaving Technology Can  Reduce Energy Costs in Your Data Center.”

80% of today’s lead consumption is due to the lead  content in lead-acid (VRLA) batteries. That still makes  lead the biggest environmental concern when using  the batteries, since exposure can possibly take place  during mining, processing, and the recycling  of the lead.  

In less developed countries where mining and/ recycling is more poorly regulated, the potential for  human exposure and environmental contamination  is still an unfortunate reality. Lead-acid batteries  can find their way into landfills and recycling of  lead in some of the less developed countries can be  conducted without the necessary processes to control  lead emissions and contamination. 

The lithium in Li-Ion batteries is not a huge concern  in terms of pollution. However, depending on  the chemistry of the Li-Ion cell, they may contain  manganese,cobalt, or nickel, which while not  considered as toxic as lead, are still classified as  toxic heavy metals, so Li-Ion batteries are not 100%  without environmental concerns. 

The good news is companies are working on the  complete recycling of Li-Ion batteries. About 80%  of the contents, by weight, of Li-Ion cells is steel  and copper, which is nearly 100% recyclable, and  technologies are being developed to recycle the rest.  The goal is for Li-ion batteries to be recycled at rates  as high as lead-acid batteries.

STORAGE AND LONGEVITY OF  BATTERIES 

Li-Ion batteries exhibit a low capacity to fade/self-discharge when stored properly. Proper storage would  have the Li-Ion batteries in a semi-charged state,  which is ideally 35-40% of the fully charged value.  This semi-charged state prevents the batteries from  potential negative impacts (safety, stresses on cell, low  voltage state) of being stored at full capacity. When  ready, the batteries can be charged to 100% and will  be ready for use. If Li-Ion batteries are stored properly  in a room temperature environment (0-25°C), they can  be stored for many years with minimal loss  of battery capacity. When VRLA batteries are not in use, it is  recommended that they should be charged every  three to six months to prevent loss of capacity and/or  damage to the cells. If not stored properly, they can  suffer permanent loss of capacity after only 18 months 

ENVIRONMENTAL IMPACT 

The good news about lead-acid (VRLA) batteries is  that they are over 99% recyclable. The bad news is  lead, which is the main component of these batteries,  is a heavy metal that can have adverse health impacts. While leaded gasoline and lead-based paints were  eliminated from use nearly 50 years ago due to  environmental and health-related concerns, over