| To ensure the integrity of any Uninterruptible Power | | | | lead acid' (VRLA) batteries( often referred to as just |
| Supply, Telecommunications 48V system or | | | | 'sealed lead acid batteries'). |
| generator, the lead acid batteries must be checked | | | | Wet cell battery maintenance can be more time |
| and maintained. | | | | consuming, as the trade off against increased life |
| Surprisingly what ever the cost of your Power | | | | expectancy is the higher cost of maintenance due to |
| Protection system, whether it is a stand alone UPS | | | | the necessity of taking specific gravity readings and |
| System or Standby Diesel Generators the most | | | | 'topping' up the cell. A visual check of wet cell |
| common single point of failure are the batteries. | | | | batteries needs to be undertaken on a more regular |
| High resistance, leakage or open circuits will cause | | | | basis as any noticeable drop in electrolyte level must |
| batteries to fail; no longer providing the expected | | | | be swiftly rectified. |
| autonomy or, in the case of a generator the inability | | | | The VRLA 'lead acid' battery is more difficult to |
| to start. The Result - loss of the site load. Then | | | | check being a sealed battery. The most common |
| suddenly you require a 24-7 emergency call out | | | | method of testing, often built into most UPS |
| engineer. | | | | systems equipment is a battery self test which is |
| Uninterruptible power supplies may have internal | | | | often carried out automatically on a weekly/monthly |
| batteries or housed in separate battery cabinets. | | | | time cycle. If the test fails the UPS system will |
| Each battery has a recommended design life, usually | | | | generate an alarm. The major drawback is if the |
| 5 years or 10 years, although these are optimistic as | | | | equipment is supporting a small load comparative to |
| they don't take into account high usage of the UPS | | | | the capacity of the equipment the battery will not be |
| Battery system caused by intermittent spikes, brown | | | | worked very hard and could prematurely fail. |
| outs or voltage fluctuations which are absorbed by | | | | The more reliable means of regular testing a battery |
| the batteries to protect your mission critical sensitive | | | | is either:- |
| systems. | | | | 1. By loading the battery to one third of its capacity |
| Even though the battery may have an operating life | | | | and carrying out a capacity test |
| expectancy stated by the manufacturer of typically | | | | 2. impedance testing -increasingly popular as it's |
| up to ten years, if it is not checked on a regular basis | | | | non-intrusive. |
| it can and will fail. In a string of 32 blocs all it takes is | | | | There are several methods of achieving the same |
| one battery to become high impedance and the | | | | result but one method is to pass a known ac current |
| complete string will be useless as the load will be | | | | through the battery and measure the ac voltage and |
| unable to draw the current it requires and as a result | | | | thus, by using Ohms Law calculate the battery |
| the load will be lost and your critical load will fall over. | | | | impedance. These results can be compared with the |
| The old batteries can be removed and new batteries | | | | manufacturer's recommended value and by keeping |
| supplied. | | | | records can be compared over a period of time |
| The most obvious signs of Battery leakage due to | | | | allowing a replacement programme to be |
| failure within the sealed lead acid battery causing the | | | | implemented when the battery impedance has |
| casing to split can be visible. Other issues of high | | | | reached a preset value. |
| impedance and open circuit are not obvious and | | | | Which ever method of battery testing you choose , |
| require regular checks. | | | | regular battery maintenance is an integral part of any |
| There are a number of different types of battery | | | | Uninterruptible Power Supply or Generator standby |
| construction but they can be loosely divided into to | | | | power protection system . |
| two common types-'wet cells' and 'valve regulated | | | | |