4 Ways to Extend the Life of UPS Batteries

Data center backup power is a crucial element to uptime and availability. During an outage, Uninterrupted Power Supply (UPS) enables the switch from utility power to backup generator power. But there is a relatively unreliable and expensive variable to most UPS: batteries.

Batteries represent three evils: They are big, they are expensive, and they are expendable. Anything you can do to prolong the life of your batteries will indeed extend the availability of your data center.

So here are four ways that data center facility managers can extend the life of their UPS batteries.


(1) Buy the right UPS battery for your data center


In a data center, UPS is designed to fully discharge the battery source within 20 minutes. This is called high-rate discharge. High-rate batteries have thinner plates and more plates than lower-rate batteries, but as a result high-rate batteries can lead to a shorter lifespan.

There are many other factors in buying UPS batteries, such as the life expectancy, voltage, front or top access, flag post or inserted post, and other considerations. For example, a small format valve regulated lead acid (VRLA) battery has a relatively low first cost but lower reliability. Meanwhile, a nickel cadmium (NiCd) battery has the best reliability and longest service life, but the first cost can be four times as much as other batteries.

Data center manager must also be aware of potential manufacturing problems such as faulty post seal design and internal connection problems.


(2) Install, operate and maintain batteries correctly


Incorrect installation can lead to shortened battery life, as can improper maintenance. Good maintenance means giving the batteries well ventilated air that is as close as possible to 77 degrees Fahrenheit, and making sure that all batteries in the string are getting air within 3 degrees Fahrenheit to ensure that some of the batteries don't age more quickly than others.

Why? Mixing batteries of different ages or internal resistances can prompt batteries to die more quickly. Regular inspections of the batteries can unveil problems such as loose intercell connections and damaged post seals, which can lead to corrosion and even fires.

Data center manager should also be aware of the battery's discharge status as well. A fully or nearly fully discharged battery that isn't recharged within 48 hours can lead to damage. Overdischarging a battery can cause recharge problems, and excessive discharging -- for example, if a data center does weekly testing of its backup systems that includes battery cycling -- can reduce battery life.


(3) Monitor the UPS batteries' capacity


When the internal resistance of a battery rises due to normal aging factors such as corrosion, and when it has increased by as little as 30%, it's time to replace them. This is most often measured through capacity testing, as most manufacturers say that when a battery drops to 80% of its original capacity, it's cooked!

Users should perform capacity testing on their batteries based on IEEE standards; in particular, IEEE 1188 or IEEE 450.


(4) Flywheel UPS in conjunction with battery UPS


When flywheel UPS is installed with battery UPS, the flywheels can often handle the shorter power outages that happen more often and can prevent the batteries from cycling. The flywheel UPS also helps to extend battery life by two years preliminary.

In addition, flywheel can filter out the 'dirty power, such as little power blips and spikes. The batteries would filter those spikes out but if you hit the batteries with those spikes, it will kill the battery life.



About Strategic Media Asia Limited


Strategic Media Asia (SMA, www.stmedia-asia.com) is a professional training program and seminar organizer for corporations specialized in data center design & build, mission critical facilities, telecommunications infrastructure, financial IT and colocation services. Currently, SMA delivers a series of critical infrastructure training courses and qualification programs in Hong Kong and Macau.


For details, please visit www.stmedia-asia.com/trainings.html.

Data Center Design: Battery-based / Static UPS or Rotary UPS?

UPSs vary greatly in physical size, weight, form factor (e.g., standalone vs. rack-based), capacity, supported input power source (e.g., single phase vs. 3-phase), technological design, and cost.

When considering the procurement of a UPS for a data center or other mission critical facility, there are a number of design and acquisition decisions to make such as:

1. The size of the load to be protected
2. The battery runtime required
3. The proper input and output voltages
4. The right type of system (i.e. on-line, line-interactive, etc.)
5. Pricing and performance seen within manufacturer product portfolios
6. The advances in technologies
7. The ideal level of redundancy (i.e., N, N+1, 2N, 2N+1, etc.)
8. The required output distribution

This time our focus will be limited to comparing 3-phase battery-based UPS and rotary UPSs that support data centers. Some of the common 3-phase UPS architectures are listed below:


- Double Conversion On-Line UPS
- Delta Conversion On-Line UPS
- Engine-coupled Rotary UPS
- Flywheel UPS


Other Single phase UPS systems (will be discussed later):

• Standby UPS (single-phase load ranges from 100 to 1,500 VA)
• Line Interactive UPS (single-phase load ranges from 0.5 to 10 kVA)
• Standby Ferro UPS (single-phase load ranges from 3 to 15 kVA)

Double Conversion On-Line UPS

This design is by far the most common type for loads above 10 kVA. A double conversion UPS is considered ‘on-line’ because its nearly ideal output waveform is derived completely from battery power through its inverter. As such, this isolates the output from the input. The input primarily serves to continually charge the battery.

Therefore, during an AC power failure, on-line operation results in no transfer time. Since 100% of the load power is converted twice, once from AC to DC (to charge the battery) and a second time from DC to AC (for the output), a double conversion UPS is inherently less efficient than offline UPS types.

These UPSs are available in a broad range of sizes for three-phase loads from 10 to 1,000 kVA. Furthermore, these UPSs can be arranged in a vast array of configurations to achieve high availability for very large three-phase data center loads.

Delta Conversion On-Line UPS

That design is a more recent topology that was originally patented and utilized exclusively by APC for its Silcon-series 3-phase UPS line.

The advantage of this topology is its energy efficiency. It achieves high efficiency by not processing 100% of the power, 100% of the time, as is the case with a double conversion UPS.

Rather, it processes only the portion of the power that is outside of the ‘window’ of an acceptable power waveform, while at the same time having an output that is on-line with load such that there is only a load step change from steady-state to full battery-load operation. As such, this technology is best suited for the highest power applications and well above 1,000 kW.

Engine-coupled Rotary UPS

A rotary UPS is one that unlike the prior approaches does not rely on electronics to pass through or recreate an output AC waveform. Rather, a rotary UPS relies on a mechanical motor and generator to create a pure sine wave output without the need for filter capacitors. Additionally, the resulting low input impedance allows the ability to handle any type of load no matter how ‘dirty’ it may be.

Also, this approach yields an ability to handle high fault currents and provide isolation from high harmonic load input currents. Finally, a rotary UPS can be configured to use direct diesel bypass. By comparison, a static (or battery-based) UPS, can only source its load from a generator in a ‘break before make’ fashion. Due to the nature of its ability to handle ‘difficult’ loads, rotary UPSs are large in size and expensive. As such, they are reserved for large loads in excess of 1,000 kW.

The advantages of Rotary UPS:

1. Most energy efficient UPS/CPS system
2. Use of stored kinetic energy
3. No batteries required, that means no chemical waste!
4. Save energy for battery room's ventilation and cooling 
5. Lowest Total Cost of Ownership (TCO)
6. Highest power factor
7. No conditioned battery room required, that means saving space
8. Long life time
9. Efficiency about 96%

Flywheel UPS

Flywheel UPS system is similar to the settings of battery-based UPS system. The rotary UPS is called “rotary” because rotating components (such as a motor-generator) within the UPS are used to transfer power to the load. The true definition of a rotary UPS is any UPS whose output sine wave is the result of rotating generation. Therefore, the UPS in Figure below, although it utilizes a flywheel as a rotating temporary energy storage source in case the utility fails, is not, by definition, a rotary UPS.

About The Blogger


Strategic Media Asia (SMA, www.stmedia-asia.com) is a leading technical training and event organizer for corporations specialized in data center design & build, E&M facilities, telecom, ICT, finance and colocation. Currently, SMA delivers a series of data center trainings and qualification programs in Hong Kong, Taiwan and Macau.

All these events / training seminars are designed to support the leadership needs of senior executives (Chief Information Officers, IT Directors / Managers, Facilities Managers, company decision makers, etc.) and to provide useful and applicable knowledge.

For detail, please visit our data center courses & training seminars at http://www.stmedia-asia.com/trainings.html.