Whenever you install an uninterruptible you put a lot of faith in the quality of every component within it and no more so than the battery set. Yet, the batteries are the one component whose reliability will degrade over time and with some rapidity. You also place a lot of faith in your chosen UPS supplier, who may choose the lowest cost blocks and mask this with a long product warranty.
Any critical power user has to install an uninterruptible power supply whether they are a datacentre, process control plant, hospital or blue-light emergency service. The easiest way to look at critical power is to picture this as the electrical source from your building incomer to the power distribution sockets and connected loads. Anything that is to be kept running during a mains power failure and protected with a high quality supply is connected to the critical power supply.
A UPS system requires a fuel source for its inverter (output stage). When the mains power supply is present, the UPS rectifier (input stage) provides this as a DC supply from a rectified mains supply (or generator supply). When the mains power fails, this DC supply is provided by a connected battery set in over 95% of all UPS installations.
Typical battery runtime (back-up time) from the battery set will be 10-15 minutes maximum at a calculated load and this is generally long enough to cover a generator start-up or ride-through a short power cut. Longer battery back-up periods may be installed for critical sites where there is no standby power generator.
What may be surprising is that battery technology has hardly changed in the last 40-50 years. Valve Regulated Lead Acid (VRLA) maintenance free batteries using a gel electrolyte being the last big development in this field. There are new technologies on the horizon and these include flywheels, fuel cells or lithium-ion batteries. Drawbacks are however that they do not provide the back-up capacity and/or significantly raise the initial capital investment.
Lead acid batteries will remain the product of choice for the foreseeable future. They are the dominant technology and mass-manufactured. Volume economies of scale have lead to low unit prices per battery block. In addition, barriers to entry for new manufacturers are relatively low-tech and more about access to lead supplies and finance for a manufacturing plant.
For any UPS supplier, it is relatively easy to source low-cost lead acid batteries from the Far East which can be very price competitive. Quality issues aside, these batteries will only have a 12 months warranty and little on-shore presence i.e. in the form of an office, warehouse or service team. To compound matters, UPS manufacturers in recent years have extended their product warranties (as a competitive tool) to 3-5 years in some cases. UPS manufacturers may also supply their systems with or without batteries, leaving the UPS supplier or installer free to put in whatever battery they need to be competitive.
As long as the battery doesn’t show a problem inside the UPS warranty period is this an issue? The answer is ‘yes’. There are generally two design-life categories of lead acid battery used with UPS systems: five-year and ten-year. These are ‘calculated’ and limited by a number of factors including application, charging regime, ambient temperature and number of charge/discharge cycles. A five year-design life battery should last 3-4 years (and 10-year design life batteries 7-8 years).
UPS systems are a type of capital equipment and larger systems should last around 10 years or more. Here are talking on-line UPS systems that are maintained and subject to annual preventative maintenance inspections. Anyone investing in such a system should also expect their batteries to last fairly well into this period, depending on usage and the battery design life fitted. If a user fits a five-year design life battery they should expect two complete battery set changes within the ten years or one if a ten-year set is installed. Anything else points to a poor quality battery or other system or environmental factors.
So how does a datacentre or other critical power user sort the professionals from those just looking to shift product on price? The answer is relatively simple: choose an independent UPS supplier or manufacturer who can demonstrate the quality of their systems and batteries. Factory inspections, test certificates, case studies, installed base and recommendations are clear markers. Also look for what services the supplier provides and whether these are sub-contracted or not. Ideally look for a UPS supplier or installer who provides a comprehensive range of UPS maintenance contracts and battery testing services, not just in your region but nationwide.
For more information or to book a battery test for your UPS system please call us on 0800 210 0088 or visit www.EcoPowerSupplies.com