UPS systems are a necessity for any critical datacenter, network closet, computer room, or engineering lab. They will often provide enough power for gas generators to kick in, or allow enough time for the systems to safely shut down. In addition, larger UPS systems provide power conditioning and protection from surges and sags. The battery of choice for virtually all UPS systems is the lead-acid battery.

There are a few reasons why lead-acid is the battery of choice; they handle recharge cycles well and are a well established technology. Further, and most importantly, they are the most cost effective solution for UPS applications. While other technologies may offer certain better performance characteristics, they typically cannot match the price-to-performance ratio of the lead-acid battery.

As with all chemical batteries, there is a lifespan associated with the lead-acid cells which make up the battery. This is because batteries rely on chemical reactions to function and these reactions can degrade the components which make up the battery. Factors such as frequent charging and discharging, deep discharging, and less-than-ideal ambient temperatures can all have a detrimental effect on the lifespan and performance of a battery.

Thus, it is very important to maintain proper testing and maintenance of UPS batteries. If there is a sudden battery failure, or if the battery capacity becomes extremely low, an expensive UPS could end up providing little to no protection for power outages or electrical sags. It is also important to maintain a healthy environment to maximize battery life and performance.

It is important to understand the capabilities of every UPS. A very important feature of any UPS is the maintenance bypass switch. This type of switch allows for electrical isolation of the UPS and its components to allow for proper maintenance. Maintenance can include anything from battery replacement to power module replacement. It is important to note that while many UPS systems will have an internal transfer switch; it does not provide the same level of isolation as an external maintenance bypass. While most larger floor-standing UPS systems typically incorporate an external bypass in their design, smaller systems may not and will require a separate maintenance bypass device.

Many UPS systems also feature hot-swappable batteries and power modules. These allow for switching out power modules and/or batteries without losing protection on the load. For true hot swapping, a UPS system must be configured with at least N+1 redundancy. Otherwise, there is a risk of running an unprotected load or losing load capacity.

Figure 1 - This shows the two operating modes of an external maintenance bypass. The “POD” sits between the utility power, the connected load, and the UPS. It can switch so that the UPS is powering the load (LEFT) or it can switch so the utility is directly power the load (RIGHT).

Figure 2 - This is what an actual external maintenance bypass looks like. This is specifically a Liebert Micro POD rack mountable unit to be used with the rack-mounted GXT3 units. The "LOAD" and "UTILITY" knockouts are hardwired terminals for connecting the load and utility, respectively. The UPS cable connects to the output of the UPS while the locking NEMA receptacle connects to the UPS input. The manually operated switch near the middle is what is used to switch between UPS and UTILITY power.

Routine battery inspection and maintenance should be done diligently and by the manufacturer’s specifications. Simply using a hard set time interval to replace batteries is not always the best solution. This is because battery life can vary greatly depending on the number and level of discharges as well as the ambient temperature. UPS systems are often placed outside of precision computer room cooling. At times, they are placed in closets with poor ventilation. These all have a large effect on the actual capabilities and lifespan of the batteries, so knowing exact battery health is vital.

UPS batteries tend not to handle deep discharges very well. So it is often a good idea to allow for some extra run-time when planning out a UPS system. If there are frequent brownouts which necessitate the UPS running on batteries often, it would be wise to over-spec the batteries to prevent frequent replacement. This will help keep the UPS running in better shape and allow for better protection in the long run.

In addition, ambient temperature control is very important in maintaining battery life. All batteries suffer from an “internal resistance” which impedes their performance. It is important to keep a constant temperature of about 65-75°F (18-24°C) to keep the battery running optimally.

Figure 3
This shows how temperature affects a battery's internal resistance. Keeping the relative resistance as low as possible will increase battery life.

Note: This section will delve into specific procedures for typical rack-mount UPS systems. For questions on large-scale units, please contact our solution specialists at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

It is important to periodically check the health status of any UPS system. Because batteries can degrade at different levels, using a set time interval to replace batteries is not best practice. Most UPS systems will have a self-test feature which will run and test battery health. It is important to know and understand these procedures.

Quick links: APC Smart-UPS On-Line, Liebert GXT3, Eaton 9130/9135

The APC SURTD5000RMXLT3U is a good example of a rack-mounted APC unit. This particular unit is defaulted to run a self test upon startup and every 14 days. To properly test the battery, the UPS will switch over to battery power momentarily. While the general battery replacement interval is 5 years, it is important to test the battery because the useable lifespan of a UPS battery can vary greatly depending on operating conditions.

Figure 4 - This is a picture of the UPS unit with the control panel area circled.

Figure 5 - An explanation of the control panel of an APC Smart UPS

Figure 6 - The circled button is used to turn on and test the UPS. To the left is the OFF button. When turned on, the UPS will by default run a self-test on the battery. When pressed and held for a few seconds, this will initiate a manual self-test.

Figure 7 - When the battery loses its ability to hold a charge, the “Replace Battery” indicator (circled in red) will light. This indicates that the battery has failed testing and should be replaced as soon as possible.

 

On this unit, simply hold and press the “Test” button on the control panel for a few seconds. The unit will respond and run a manual self test. The UPS will power the connected load via battery power for a few minutes, and then assess the health of the battery. Note that the self test runs automatically every 14 days by default. This setting can be changed using PowerChute (explained below).

This particular unit and virtually all of APC’s units can be programmed through the serial console, through an optional (standard on some models) network management card, or using APC’s PowerChute software. This is how the self-test interval is set. It is recommended not to disable the self test and to periodically check the device to confirm everything is in good working order.

PowerChute works through the serial port of the device and is a client program which can configure and monitor an APC UPS. The personal edition is free and allows for a single computer to manually change settings on one UPS at a time. It can also be used to assess the health of the UPS and view certain status that cannot be viewed through the front display.

Figure 8 - A screenshot of PowerChute Personal
There is also a PowerChute Business Edition which allows for centralized management of multiple devices through one common console. For licensing information or if you’d like to discuss PowerChute capabilities further, please contact a Mirapath solution specialist at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Figure 9 - The Business Edition allows for network management. This screen shows the battery and load status of the UPS.

The Liebert GXT3 has similar conventions for battery testing. Below is a picture of the unit with its control panel circled.

Figure 10 - This is a picture of the GXT3 with its control panel circled.

Figure 11 – Detail of a Liebert GXT3 UPS control panel. This particular unit has two load indicators for each output line (L1, L2, N).

According to Emerson, the UPS should be checked every six months. The procedures include checking the UPS status as well as the UPS functions. The two procedures are outlined below.

1. Check whether the UPS is faulty: Is the Fault Indicator on? Is the UPS sounding an alarm?
2. Check whether the UPS is operating in Bypass Mode. Normally, the UPS operates in Normal Mode. If it is operating in Bypass Mode, stop and contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
3. Check whether the battery is discharging. When the utility input is normal, the battery should not discharge. If the UPS is operating in Battery Mode, stop and contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

1. Press the Standby/Manual Bypass button to check whether the buzzer and indicators are normal.
2. Press the On/Alarm Silence/Manual Battery Test button to check again whether the indicators are on and the UPS is operating normally.
3. Press the On/Alarm Silence/Manual Battery Test button for three seconds after Inverter Mode. The UPS should initiate a battery self-test. Check to determine whether the battery is operating normally. If not, stop and contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

The unit also features an auto-battery test with 1, 2, 3, or 4 week intervals. This will need to be set using Liebert’s UPS configuration program, which is included with all Liebert UPS units. The client software is installed on a computer and communication is handled through the standard USB port on the back of the UPS unit.
Configurable parameters include the following:

1. Select L-N output voltages to match local voltages.
2. Enable/Disable Auto-Restart.
3. Select frequency converter operation with a fixed output frequency of 50 or 60 Hz.
4. Set the Low Battery Warning alarm time from 2 to 30 minutes.
5. Enable/Disable the Auto-Battery test.
6. Set the Auto-Battery test to 7, 14, 21 or 28 days.
7. Specify the number of external battery cabinets connected to the UPS to adjust the remaining run time calculations reported by Liebert software products.
8. Modify the shutdown setting of the terminal block (for information on pin assignments, see Table 2).

Liebert MultiLink monitors the UPS continuously and can shut down a computer or server in the event of an extended power failure.

Liebert MultiLink can also be configured for use without the USB cable when the Liebert IntelliSlot SNMP/Web card is installed in the UPS. Additionally, Liebert MultiLink can be configured to coordinate shutdown across the network with other computers running Liebert MultiLink when you purchase a Liebert MultiLink License Kit. For more information about the Liebert IntelliSlot SNMP/Web Card and Liebert MultiLink License Kits, contact a solution specialist at This e-mail address is being protected from spambots. You need JavaScript enabled to view it and we will gladly help you with any issues you might have.

Several option cards are available for use in the Liebert IntelliSlot port of the Liebert GXT3. The Liebert IntelliSlot SNMP/Web Card provides SNMP and Web-based monitoring and control of the UPS across the network.

The Liebert IntelliSlot MultiPort 4 Card allows installing Liebert MultiLink software on four computers and coordinate shutdown in the event of a power failure.

The Eaton 9130/9135 series of UPS are a tower or rack mounted online UPS system from Eaton. They are comparable to the GXT3 and the APC Smart-UPS Online systems. The 9130 ranges from 700-3 kVA while the 9135 ranges from 5-6 kVA. Larger models include the 9140 and the 9155 series which are comparable but have larger capacities.

Figure 12 – This is a front view of a rack-mounted 3U 9135 coupled with a 3U external battery cabinet for extended run-time. The display on the UPS can rotate and is where settings can be changed manually.

Figure 13 – This is the rear view of the unit showing an L6-30P input and (4) L6-30R outlets.

Figure 14 - This is a close up of the UPS panel with an indication of the buttons and indicators.

This UPS defaults to either a 30 day (for the 9130) or a 7 day (9135) auto self-test of the battery. The 9135 has the option of changing to no test, daily, weekly, or monthly tests. The 9130 has the option of changing to no test or 30 day only. The unit also performs an automatic self test each time it is turned on.

The External Battery Modules (EBMs) are included in all testing and do not require separate testing. This is dependent on programming the existence of EMBs into the module.

Battery health status can also be checked by using the UPS monitoring software. There are several options available and most of these options are available free of charge. Consult a solution specialist at This e-mail address is being protected from spambots. You need JavaScript enabled to view it to inquire about options.

To run a self test on this unit, access the control panel and scroll to the “Maintenance” menu. Then, scroll to the “Manual Batt Test” menu and press the enter key on “Yes.” This will perform a brief manual self-test of the battery. Any abnormal status found will be indicated by the “Battery Indicator” lighting up.

This UPS can be configured through its front control panel. These configurations can change, amongst other things, the battery self test interval, local settings, output settings, battery settings. Additionally, the front panel can display most pertinent information about the UPS.

Additionally, all configurations and monitoring options can be accessed using one of the many Eaton tools available. Please contact a solution specialist at This e-mail address is being protected from spambots. You need JavaScript enabled to view it to discuss your options.