Uninterruptible Power Supply – External Batteries Testing

Batteries are at the heart of most uninterruptible power supplies (UPS) and power protection solutions. (Some run on a flywheel energy storage device, but most contain batteries). They provide continuous power to protected loads in the event of a mains failure, allowing them to continue operating. Until a generator or alternative power source comes back on or providing enough time for equipment to shut down or for a short-term power outage.

External battery “strings” or “kits” (a set of extra UPS batteries arranged in blocks that provide extended run time – run time longer than the time supported by the internal UPS battery) are often a big part of an uninterruptible power supply. However, an entire battery is only as good as its weakest battery. Therefore, it is extremely important to regularly check UPS batteries and battery circuits for “weak links” that should be replaced immediately – even if they have not yet reached their design life, which for UPS batteries is five to ten years.

There are several methods of electrical testing of UPS batteries:

• Automatic battery pack test (performed by the UPS itself).
• Load bank discharge test or testing of the battery pack, strings, and individual cells.
• Electrochemical testing.

Many uninterruptible power supplies are design to test the batteries every 24 hours and beep if a fault or battery condition detected. The test subjects the battery to a load and monitors discharge efficiency. However, this is a simple test that does not give detailed information, but only a general idea of the condition of the battery pack. Battery packs usually age evenly, but individual battery packs can fail earlier than others and stop maintaining sufficient charge levels, which can lead to a reduced load for the entire pack. Visit also: Sprinter Battery price in Pakistan

A more accurate and reliable method of testing batteries or battery packs is to use a load bank that puts a load on the pack, from which periodic readings can be taken to assess discharge efficiency. But even this has its limitations. The disadvantage of load bank testing is that system reliability is reduced during testing, which is unacceptable for critical applications such as hospitals or financial processes.

For large battery sets, testing individual units is much more reliable and does not require additional man-hours because it can included in routine maintenance. It should include a visual inspection to make sure the battery cases are intact and show no signs of aging, such as warping and electrolyte leakage, which can sometimes seen around terminals and valves.

Battery sulfation:

Because UPS batteries undergo an electrochemical process, they can deteriorate over time (months or even years). When batteries sulfate, lead sulfate crystals form in the electrolyte and on the plate terminals. Reducing charging efficiency and preventing normal operation. They can brought out of this condition. (If detected at an early stage and the sulfation level is not very high). By charging them with increased current for about 12 hours. Care must taken, however, as this process itself can generate heat. If the battery is not recover in this way. It must immediately removed and disposed of (by an authorized technician) and replaced.

Impedance testing:

Impedance testing can identify battery blocks that are close to failure. As batteries age, their internal resistance (which limits the flow of ions between positive and negative plates) increases. To test impedance, an AC voltage corresponding to the size of the Ah battery is applied across probes attached to the terminals of the battery pack. The impedance (in milliohms) measured, recorded, and compared to the manufacturer’s published data and/or previous records.

Electrochemical Testing:

Electrochemical testing is based on measuring the frequency response to voltage and current signals. Applied to the battery with probes attached to the positive and negative terminals.

And electrochemical testing is a non-invasive method that uses the principle of frequency response analysis (FRA). To compare the measured data with algorithms for known battery conditions, specifically sulfation and electrolyte drying. This problem is a major cause of UPS battery failure and poor performance. Although electrochemical testing was originally only possible in laboratories. It can now applied to UPS batteries with a specially designed portable tester.

Because batteries are so important to an uninterruptible power supply and their monitoring and testing is relatively quick and easy. Care must taken to do this with accurate regularity to ensure the reliability of power protection solutions.

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