These days UPS systems support a variety of markets and applications. The principal function of a UPS is to convert a DC supply to AC in the event of mains failure, making batteries the key components of any UPS, as Yuasa explain
It wasn’t all that long ago that it was common practice to have large centralised computer systems supported by UPS equipment. These needed typical standby power autonomies of 30 minutes or greater. Due to the physical size of these computer systems, large amounts of expensive floor space were also required to accommodate the UPS equipment.
The personal computer age saw UPS systems developed for use on or under the desktop with a single battery providing power for sufficient time to save work and shutdown. To keep pace with these developments the physical size of VRLA batteries needed to be reduced and be capable of delivering as much of its available energy as possible in ever shorter periods of time.
The modern world
The advent of the internet and cloud computing has meant that things have come full circle for UPS systems, with large computer centres required by internet service providers and enormous data centres springing up all over the world to store the huge amounts of information now being generated by applications unheard of a decade ago.
Conventional industrial VRLA batteries were designed to discharge over a long duration - typically ten hours plus. With a slower discharge period, the electrochemical reaction taking place within the battery becomes more efficient allowing a greater Ampere hour capacity to become available. Conversely, with a faster discharge the electrochemical reaction is less efficient and therefore battery capacity is reduced.
VRLA design engineers are constantly looking into technology improvements to improve the efficiency and performance of the battery. For example, a reduction of internal resistance within the battery can improve the mass transport of active materials within the electrochemical reaction.
However, while striving for optimum performance, care must be taken not to trade-off other desirable characteristics such as service life, gas recombination, operational safety and reliability. Relatively low cost batteries can be produced by ignoring these characteristics to achieve apparently improved performance quite easily. However, such low cost batteries usually have a price to pay in terms of inferior quality, reduced service life and reliability so, to avoid being let down by such a product, it is recommended that batteries be purchased from known, established manufacturers.
A recent major refurbishment of a data centre UPS system illustrates the need to specify the highest quality batteries. Fujitsu Services is a European IT services company with multiple data centres across the UK, Europe and worldwide. In one of its UK centres, the original Yuasa UPS batteries were due for replacement after over nine years of operation. The UPS systems (ten APC Galaxy 800kVA units) had been supplied by Schneider Electric Power & Cooling Services with external battery facilities using approximately 4,800 Yuasa EN160-6 batteries.
Jim Hole, Fujitsu’s site facilities manager, commented, “The original UPS systems and batteries had performed faultlessly since installation almost a decade previously and we were generally pleased with the service received from Yuasa and Schneider Electric, so there was no need to look much further when it came to refurbishment. In this industry there are generally two types of battery to choose from, both good quality but one slightly better than the other with a ten year life span.”
He continued, “Once we had agreed the contract, the replacement of the batteries and capacitors on the existing UPS systems went as smoothly as one can expect for a project of this size. Yuasa and Schneider Electric combined to implement a very complex refurbishment and showed themselves to be very willing to overcome any obstacles such as the logistical difficulties encountered in trying to move a large number of very heavy batteries in sometimes confined areas. In addition, the installation of such a large number of batteries is a very laborious and intensely physical task with the repetitive checking and rechecking of connections being a critical element.”
Besides the replacement of almost 4,800 batteries for the existing ten UPS systems, a further 1,200 batteries were required for a new APC heating and air conditioning (HAC) cooling installation at the site - the so-called Cube room. This means that almost 6,000 Yuasa batteries are providing constant online uninterruptible power from four battery rooms on the site - one for the Cube HAC system and one each for the three-phase electricity supply in the building.
Hole concluded, “The essential nature of a data centre such as this is to provide up-time guaranteed to a specified level and without Schneider’s APC UPS backed by Yuasa’s batteries we would not be able to meet the high expectations of our customers.”
Yuasa Battery Sales
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