The battery system in a UPS represents the heart of the power protection benefit. This key element performs two functions: (1) it delivers energy during a power outage, and (2) it stores energy efficiently for extended periods of time. That stored energy is instantaneously available when needed to support the critical load on the UPS. In order to perform the above functions reliably, the charge level of the battery must be maintained. At the same time, battery charging should be controlled to maximize system efficiency and, more importantly, to maximize the float service life of the battery system.
Two types of battery charging schemes have traditionally been used for UPS battery systems. The older and more commonly known is the “float” charge, which involves applying a constant voltage charge to the battery continuously for purposes of maintaining full charge during day-to-day operation of the UPS. This works quite well in many conventional battery applications. However, battery life may not be optimal, due to overcharging, for batteries that are used very occasionally as in standby applications such as a UPS. In a UPS, the battery system may sit in float mode for many months, without ever experiencing a discharge. Float charging for long periods of time means that “trickle charge” energy is constantly forced into a battery which is effectively already full. This results in very gradual degradation of the lead plates (positive grid corrosion), and it can impact float service life.
Standby applications are better suited for “opportunistic” charging schemes. The system Eaton® utilizes is called ABM technology, which is essentially a set of charger controls and automated battery tests. It is implemented in Eaton single-phase UPSs from 500 VA to 18 kVA and three-phase models from 10 kVA to 3.3 MVA. Opportunistic charging schemes like ABM allow for periods of time where the battery is being fully charged, and periods of time when the charger is disabled. This reduces the time that the battery is subject to grid corrosion when compared to a traditional float charger — a reduction in grid corrosion that yields a measurable increase in battery life for UPS applications.
ABM Operational Summary
As shown graphically in figure 1, ABM consists of three operating modes:
The UPS enters the charge mode under any of the following conditions:
In charge mode, constant voltage charging of the batteries is used to recharge a discharged battery after a power outage, or whenever the ABM process is restarted. Charge voltage target is set to the manufacturers’ float level, and charge current is greater than 0.1 C A. Constant voltage charging lasts only as long as it takes to bring the battery system up to a predetermined float level (there is a 100-hour maximum time limit). Once this level is reached, the UPS battery charger remains in constant voltage mode, maintaining a float level. The current is at trickle charge levels during this time, and a 24-hour clock is started. At the end of 24 hours of float charging, the UPS automatically performs a battery test (see figure 1) at two different load levels to verify that the battery is performing, and to collect data for comparison to previous and subsequent automatic battery tests. If the test fails, an alarm is activated on the UPS and also through the remote monitoring system that may be connected to the UPS. At the end of the test, the charger resumes constant voltage mode and remains in that state for an additional 24 hours.
Rest mode begins at the end of charge mode; that is, after 48 hours of float charging, and after a successful battery test. In rest mode, the battery charger is completely turned off. The battery system receives no charge current during this mode, which lasts about 28 days. Then, the charge mode is repeated as described above. Since the battery clearly spends most of its time in rest mode, as a result, the following benefits are realized:
During rest mode, the open circuit battery voltage is monitored constantly, and battery charging is initiated if any of the following occur:
There are two other battery tests that are performed as a part of the ABM cycle. The first is meant to detect battery conditions which could lead to thermal runaway. The bulk charging period is timed and if the float voltage is not reached in a predetermined time, an alarm is triggered and the charger is shut down. The second test is performed after the charge cycle is completed (i.e., at the beginning of rest mode). The battery is discharged at about 15% load for up to 6 minutes, then at 50% load for 45 seconds.. Upon reaching this point, the battery voltage is measured. If the voltage is below a specified threshold, dependent on the load, then an alarm is signaled indicating the battery is nearing the end of its service life and should be replaced.
ABM may be disabled by the user or an Eaton field technician at any time. In this case, the UPS battery charger operates as a conventional float charger only. This is recommended when a wet cell or flooded electrolyte battery is used with the UPS. ABM is intended for use with VRLA batteries. As a result, wet batteries do not benefit from ABM controls.
Many observers express concern regarding the ability for the battery to maintain capacity if called upon to support the UPS near the end of its rest mode. In other words, how much battery capacity is available on day 27 of a 28-day rest mode? Using a 15-minute battery as an example, under this condition, the battery would provide all but about 30 seconds of its 15-minute backup time. This is proportionally true for other battery sizes, as well. The intent in selecting the 28 day rest period is to limit the loss of capacity to approximately 5%.
The ABM process above describes the benefits of using a “opportunistic” charging scheme. Those benefits, specifically extended service life, are in fact substantiated by data and empirical testing performed by Eaton as well as other independent sources. Some of this testing is recent and some of it was performed as many as 25 years ago.
ABM is not a new battery management feature. In fact, Eaton has been using ABM in its UPS products for 27 years, and it has proven itself beneficial in the field for more than two decades.
Note that in figure 4, the curve identified as “23/23 days” represents a float charger, and ABM (as implemented today) is best represented by the curve labeled “12/23 days.” At an ideal 25°C (77°F), there is a theoretical increase of six years in battery service life reflected in this analysis.
The above information shows a clear benefit of cyclic charging in UPS applications, both in simulated and in actual performance tests. These results would not be expected with non-VRLA batteries or in applications such as motive power chargers where the battery is discharged/recharged daily and therefore not deployed in a standby application.
ABM is unique in the UPS industry, but similar opportunistic designs are utilized by battery manufacturers and battery charger designers worldwide. The criticality and cost of the battery subsystem of any UPS dictates that special consideration be given to battery longevity. Additionally, with environmental concerns relating to battery removal and disposal becoming more prevalent, it is desirable to reduce the frequency of battery replacements during the life of the UPS electronics. ABM offers a significant benefit over conventional “battery monitors” which don’t provide charging control, and “multi-stage chargers” which protect the battery, but do not provide useful extension of battery service life.
Over the past 27 years, ABM has proven itself in both large and small UPS products, from the desktop to the data center, and from the medical lab to the factory floor. Anywhere a UPS is installed, a battery system is depended upon to provide backup power protection for critical business processes and even for personnel safety. The battery is all too often ignored as a maintenance-free product, not requiring attention or inspection. This neglect, though common, can be costly and possibly disastrous. The ABM system, by its nature, helps to provide early detection of problem batteries and thus protect the battery from unnecessary failures like electrolyte dry out and thermal runaway, while functioning to extend the useful life of this key component of power quality.
Automation: Smarter Days Ahead
Imagine the ability to deploy hundreds or even thousands of power distribution units (PDUs) at the simple touch of a button — without countless hours spent determining configuration parameters and assessing application nuances. Or even, a day when firmware is no longer required on uninterruptible power systems (UPSs) because software alone will have the capability to modify, upgrade, add or remove devices.
The reality of these scenarios may be closer than you think, compliments of artificial intelligence (AI), the ability of a digital computer or computer-controlled robot to perform tasks commonly associated with intelligent beings. Fueled by an explosion of data, rapid growth in cloud computing and the emergence of advanced algorithms, business adoption of AI is on the rise, according to a recent survey of IT decision-makers by CCS Insight. With eight percent of respondents already using, testing or researching AI within their organizations, those surveyed estimated that within the next 24 months, as much as 30 percent of their business applications would be enhanced with machine learning.
“Artificial” is very real to big companies
Already becoming mainstream among major players like Microsoft, Salesforce, Google and IBM, AI is now prompting some power manufacturers to take note, as well. In fact, many predict that artificial intelligence will likely drive the power devices of the future — benefitting end users by reducing costs, enhancing productivity and alleviating risk.
Among the most anticipated advantages of AI in the power protection arena is the promise of dramatically faster and simpler UPS and PDU deployments. Currently, network administrators tasked with installing these devices must wade through a cumbersome array of settings and operational parameters. Yet if an AI-afforded algorithm was able to evaluate the surrounding network environment, the entire deployment process could be seamlessly automated — resulting in tremendous time savings and bolstered productivity for an organization.
Human error is a thing of the past
AI also has the potential to help companies diminish risk. Because most network administrators are not power experts, it can leave a large margin for error during the deployment process, with even the slightest improper assessment or incorrect assumption potentially resulting in costly mistakes. Yet tomorrow’s PDUs and UPSs will likely be smart enough to automatically determine their optimal environment and adjust all default parameters accordingly. Drawing on its intelligent capabilities, an AI-driven UPS might even execute critical operating decisions, such as switching power to a different source or alienating attached equipment if an issue arises in its environment.
Peeking a little further down the road, experts foresee AI-driven power protection devices being controlled by software-defined technology, which would eliminate the need for technicians to install firmware on either UPSs or PDUs. With all equipment operated from a management platform, administrators could make changes on the fly, saving organizations even more time and money while significantly enhancing reliability and uptime. Devices capable of supporting this arrangement will require built-in artificial intelligence — and the good news is, this is already in the developmental stages of power technology. The future is (almost) now.
Your UPS is like your car: It requires scheduled and consistent maintenance in order to run at its optimal potential! Learn more about the UPS LifeCycle and the steps you can take to prolong the life of your UPS in this infographic. Contact Us today!
What is Power Distribution?
Power distribution is facilitated through different pieces of equipment that take the power
conditioned by your uninterruptible power supply (UPS) and send it to your IT equipment.
Power distribution solutions can manage and even control energy consumption in smaller
environments as well as large data center applications. Distributing power efficiently results
in reduced operating costs and increased reliability.
Rack power distribution units, also known as rack PDUs, are a key component to any IT environment. They do exactly as the name suggests and distribute power to network equipment within racks. A common misconception is that they’re just power strips, and at first glance, they even look like it, but modern rack PDUs provide benefits a simple power strip cannot. Some of the valuable features include network connectivity, environmental monitoring and remote access, but we’ll get more into that later. This guide should help you get familiar with power distribution ,gain interesting insights and learn some key considerations for future IT investments.
Which UPS is right for you?
To determine the level of protection you require from a UPS consider the following criteria:
It’s clear that lithium ion (Li-ion) batteries stand poised to deliver some dramatic changes to the field of data center uninterruptible power supplies (UPSs), mainly due to their longer lifetime along with reduced weight, footprint and cooling requirements compared to lead-acid batteries that are commonly used in UPSs today. In this post, I’ll try to paint a picture of just how dramatic that change might be in small to medium-size data centers (and, in a future post, I’ll discuss potential impacts for facility-scale UPSs).
For starters, valve-regulated lead-acid batteries (VRLA) take up significant space. This is one of the reasons why large, or even medium-size companies, typically don’t place them in the IT “white room.” What’s more, many organizations in recent years have been raising the temperature of their data center server rooms to save on cooling costs, keeping in line with guidance from organizations such as ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers). IT equipment and UPSs can tolerate the higher temperatures just fine. VRLA batteries, on the other hand, will age and die prematurely at those higher temperatures.
For all of these reasons, companies tend to create battery rooms specifically to house their VRLA batteries. Li-ion technology promises to enable a dramatic reduction in the size of these rooms, by a factor of 2 to 3, simply because Li-ion batteries pack so much more energy into a much smaller footprint. This will increase the footprint available for IT space while also reducing cooling requirements, which saves on both capital costs and ongoing operating costs.
What’s more, in some instances Li-ion batteries may obviate the need for separate battery rooms altogether, by enabling batteries to be installed in the IT room along with the UPS. This is especially likely for small- to medium-size data centers. The strategy frees up useful space, simplifies installation and positions the UPS and associated batteries closer to the IT load, which provides better protection from any potential upstream electrical issues.
Similarly, companies that use scalable and adaptable integrated data center architectures such as Schneider Electric InfraStruxure, could benefit further from Li-ion technology. With such architectures, IT racks, power and cooling components are built and tested as part of an integrated data center solution which can then be expanded as necessary over time. Li-ion batteries will make these integrated “pods” even more space- and energy-efficient than they already are, while delivering the same benefits associated with having the UPS/battery combination close to the IT loads they protect, and easily scalable to keep up with data center growth.
In addition to reducing space and energy requirements, Li-ion batteries last twice as long and require less maintenance than their VRLA counterparts. They also come with advanced battery monitoring systems (BMS), giving IT groups easy, remote access to a reliable measure of the “state of health” and “state of charge” for their batteries. And with less maintenance to perform, that means fewer non-IT people need to be in the data center, which addresses a constant concern for IT groups.
I expect we’ll also see great improvement in smaller, single-cabinet UPSs thanks to the combination of higher density power electronics and Li-ion batteries. A cabinet that today supports about 60 kVA with 10 min of energy storage with VRLA batteries, may one day protect 150-200 kVA with that same 10 min. of storage using Li-ion batteries, effectively more than doubling its power density. Such density improvement should substantially change the old knock against UPSs, that they’re “necessary but bulky.”
With this paradigm shift, it is also not difficult to imagine more power protection integrated right into IT racks, because it will take up far less space and require dramatically less frequent maintenance.
These are just a few of the ways I expect Li-ion batteries will change the 3-phase UPS landscape in data centers in coming years. I’d love to hear your take on the topic, so feel free to let me know using the comments below. And keep an eye out for my next post on what Li-ion technology will mean for large data centers and facility-scale UPSs.
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