Battery Life and Death

The battery industry in India has more than doubled in the last four years and is still expanding at a rate of over 20 per cent per annum. This growth can be attributed to the automotive segment as well as to other industrial sectors, which are powered by inverter and UPS usage, in telecom, railways, power and other industrial applications. With the country facing power shortage in several pockets, the usage of inverters and UPS has gone up significantly, hiking the usage of batteries as well.

By Srabani Sen

Monday, July 20, 2009: Even till a couple of years back, batteries lasted for more than four years but today’s batteries are engineered to last only for 18-24 months because design and technology are advancing at a high pace and customers demand products with the latest technologies. “Hence, manufacturers are consciously designing batteries to last for one-and-a-half years only,” according to an industry analyst.

It is a fact that batteries play a pivotal role in enhancing the life of inverters and UPS. However, the opposite also holds true. Proper circuits in inverters and UPS help in increasing the life of batteries but consumers usually complain of battery problems and blame them for affecting the lives of inverters and UPS. Therefore, it is imperative to acquire the right knowl­edge about the technology, functionality and maintenance process of batteries.

Industrial applications have unique power needs, so the choice of battery is crucial. While consumer products require high energy density for different designs, industry requirements always demand durability and reliability. “Ageing of a battery depends on the depth of discharge, charging methods, maintenance procedures or lack of them, and environmental condi­tions,” says Anil Joshi, AGM projects, Artheon Group.

“One should ensure that a battery works well within its designed operating limits. There are, however, further measures that can be taken to increase battery life,” informs Avnish Arora, vice president, HBL Power Systems Ltd. Epower seeks advice, recommendations and suggestions from the experts in this domain, on how to enhance not only the life of batteries but also of inverters and UPS.

The battery is an energy storage device and inverters convert this energy for usage in homes and computers. If retention of storage in the battery is less or if the battery has a fickle technology, even a good inverter cannot retrieve energy. A strong technology definitely enhances the performance of an inverter or UPS. If power cuts are commonplace and occur for long durations, customers should choose a battery with tubular technology or double thickness plates technology, for these batteries last longer.

Good maintenance:

Proper maintenance of a battery not only elongates its life but also the life of the inverter and UPS. One should regularly check the water level of the battery and engage in regular topping as this enhances its life. Tech knowledge: One should inquire about the technology of the battery. If it is not a tubular or double thickness plate design, then it should not be used for inverters. A battery must have a water level indicator and its water stor­age must be more than that of ordinary batteries. This diminishes the chance of the battery drying up. Maintenance free batteries are not suited to frequent and long power cuts.

The extent of battery life is dictated by the right temperature, the number of times the battery has been discharged and recharged and the quality of the battery charger. Since a UPS lasts longer than batteries, selecting a model that has user replaceable batteries is important. A load test is essential to check the integrity of the battery. The UPS should be able to effectively power a load close to the backup time professed by the manufacturer.

The range of batteries available in the market include flooded LA, sealed maintenance free (SMF) and tubular batteries. The flooded LA battery doesn’t have any safety features. It is a potential bomb waiting to explode, if not handled properly. It requires frequent water topping and also emits acidic fumes, which are injurious to health. Tubular batteries, though a finer option, take a long time to get fully charged. The best option, therefore, is the valve regulated lead acid battery, which contains safety aspects, is sealed to prevent emission of acidic fumes and is maintenance free, not requiring any water topping.

Cutoff mode: All inverters and UPS

Batteries of inferior quality and poor technology yield less capacity than promised. They do not get fully charged and, hence, cannot supply full energy to the inverter. This reduces the backup time for the user. Also, in such batteries, charging does not get cut off, resulting in excessive charging. This enhances electricity consumption, increasing chances of inverter failure. One should opt for batteries that are specially designed for latest high technology inverters and UPS.

Choice of technology:

Tubular and double thickness plate battery technol­ogy is considered for deep discharge batteries, which are best suited to Indian conditions, where lengthy and frequent power cuts are a way of life. Water level indicators are a must for easy mainte­nance and pollution prevention. Features like self discharge, low internal resist-have the provision of cutting off charging once the battery voltage reaches a prede­termined level and enters what is called, ‘float charging’ mode. This feature doesn’t work in many inverters and they don’t cut off the charging once the battery voltage has reached the specified level. This can lead to battery explosion.

If more than one battery is used in a string, a battery equaliser is requisite. It is important to enhance the life of the batteries and also to increase the backup time that one gets from them.
High charge efficiency:

All lead acid batteries follow the ‘Arrhenius theory’— for every 10 degree rise in temperature, battery life comes down by half. So, one needs to pick a battery which has high ance and heavy duty grids are essential features, too.

Pressure rise:

Checking the water level regularly and water topping peri­odically greatly enhances the life of the battery as well as the inverter and UPS. Several factors contribute to the rise of temperature and pressure. Excessive current or a high ambient temperature will cause the battery temperature to rise and the resulting expansion of ac­tive chemicals will consequently cause the internal pressure in the cell to esca­charge efficiency so that the surplus energy isn’t converted into heat, heating up the battery.

Low self discharge:

If the discharge depth of a battery is 30 per cent, one gets about 1,200 cycles, whereas if the dis­charge depth is 80 per cent, the life of the battery can come down by one-third, thus, the necessity to pick the right capacity of battery. Batteries with low self discharge rates are better. They are also required for inverters as they are seasonal and during off season, may not be used for months at a time.

Proper charging:

If charging is conducted through pure direct current voltage/current, it affects the life of the battery. LA flooded batteries require charging on the field and the life of the battery depends on the quality of charg­ing. SMF batteries come charged and, hence, don’t face this problem.
Flooded and tubular batteries don’t generate full backup if they are charged/ discharged at a high current rate. This problem doesn’t exist in SMF batteries and that’s one of the reasons why it is used in UPS, solar and ebike/electric vehicle applications.

Late overcharging also causes a rise in temperature but a more worrying fact is that overcharging can cause the release of gases, resulting in even greater build up of internal pressure.

Buyers’ guide:

One should choose batteries that are energy efficient and technologically superior and are cre­ated using deep cycle technology and tubular and double thickness plate bat­tery. This enables the batteries to get charged in lesser time, while providing longer backups.
While buying a battery for UPS or inverters, it is imperative to be sure about a few things—is it going to be used indoors or outdoors? How long will it supply power for? Will it match the voltage output? Also, one has to make sure that the UPS battery has a built in surge suppressor and warranty for added protections. Finally, one should do not settle for cheap brands—investing in a high quality battery is a good decission. A cheap but faulty unit will not just damage the devices but could also cost much more in the long run.

Proper maintenance:

Usually, cus­tomers lack knowledge of batteries and are not aware of proper maintenance pro­cedures. It is essential to know what the fitting environment is in which to place a battery—often it is found that people dump the battery in places exposed to direct sunlight or area prone to dust and heat, affecting the latter’s life. A battery battery should be kept at a cool, dust free and ventilated place. Batteries attract dust, dirt and sulphation over time.Keeping them clean will avoid problems and enhance life.

Deep discharge protection:

A bat­tery must be protected from discharg­ing entirely. Batteries should not be discharged below a certain level. The battery deep discharge protection is, therefore, required because a deeply discharged battery is difficult to revive and recharge.

Overcharge protection:

Overcharg­ing takes place when a battery continues to get charged with high current even after getting fully charged. Such charging bulges the battery and reduces its life. Hence, battery overcharging protection is necessary.

Undercharged:

Undercharge means partial charging or erratic charging pattern. This normally happens when the battery is not fully charged or put in discharge mode. This partial charg­ing also reduces the life of the battery. Hence, it is important that the battery is put in charge mode after discharge for the duration specified by the manu­facturer.

Battery is an integral and most impor­tant constituent of backup power systems like UPS and inverter. The most likely cause of premature failure of a battery is abuse, subjecting a battery to conditions for which it was never de­signed. Uptime of a UPS and inverter is largely dependent on the battery chosen. One bad battery can ruin an entire string and bring the system down during some interruptions. Battery failure is a major cause of UPS/inverter load loss and system downtime.

Apart from obvious physical abuse, the following examples should also be considered abuse, whether deliberate, inadvertent or through poor maintenance. Generally, the following factors which af­fect battery performance and life should be known to the end users:

• Drawing more current than the battery was designed for or short circuiting the battery
• Using undersized batteries for the application
• Depth of discharge
• Rate of charge and discharge
• Time between two successive charge and discharge cycles
• Operating temperature
• Overcharging: either to too high a voltage or for too long a period
• Undercharging (partial state of charge operation)
• AC ripple
• Operating or storing the battery in too high or too low ambient tempera­tures
• Using chargers designed for charg­ing batteries with a different cell chemistry.

Selection of battery: A battery can be for float application or deep discharge. However, wrong selection of a battery also affects its performance. Hence, one should specify the usage pattern for selec­tion of the right kind of battery.

Maintenance free batteries may cost 25 per cent more than the normal ones, but they are worth going in for. These batteries are designed for 1,200-1,300 cycles (one charge and one discharge = one cycle) and run for 3-4 years.

So the bottomline is, wrong usage, wrong application and lack of knowl­edge reduce the lifespan of a battery. It is a myth that the wrong battery affects the performance of an inverter or UPS. It only affects the output. It is also the other way round. If the circuit of the inverter or UPS is not correct, it affects the performance of the battery. A consumer can take physical care of the battery, environment, etc, but the right technicality, right integration of inverter/UPS and the battery is not in their hands; that is the responsibility of the manufacturers.

Battery management: Maintenance of batteries plays a critical role in avoiding sudden or unexpected failures, which ultimately leads to failure of UPS or in­verter system. UPS or inverter application being a critical application, it is advisable that certified and technology proven batteries must only be selected for such applications.

Battery management is essentially the method of keeping the cells within their desired operating limits during both charging and discharging either by controlling the load on the battery or by isolating the battery from the load if the load cannot be controlled.

Norms & standards: The small time
Manufactures who make batteries do not follow any standard or quality norms. A customer should, therefore, be alert while buying a battery. A low quality battery may fail after a year of service, whereas a high quality battery can last for over three years.

The temperature and the battery’s charge should be checked at regular intervals. Also, the water level should be topped off intermittently. Proper storage is also an important factor as im­proper storage will shorten the life of the battery.

Certifications:

Another helpful tactic is to look for certifications and agency approvals like UL, VDE, CE, etc, printed on the batteries. These approv­als are time consuming, difficult and expensive for the battery manufacturer to obtain. Normally, educated people can take care of batteries themselves, but it is advisable that they take annual mainte­nance services from the manufacturers as people who give these services are experts.

Temperature effects:

Apart from the gradual deterioration of the battery over time, temperature effects can lead to premature failure of the battery. This can happen even under normal operating conditions if the rate of heat generated in the battery exceeds the rate of heat loss to the environment. In this situation the battery temperature will continue to rise, resulting in ac­cidents.

Ageing process:

When a battery reaches its specified lifetime, it does not stop working abruptly. The ageing process continues at the same rate as before so that a battery whose capacity had fallen to 80 per cent will probably continue working when its effective capacity will fall to 60 per cent of its original capacity. There is, therefore, no need to fear a sudden death when a battery reaches the end of its specified life. However, a weak battery will defi­nitely affect the output of an inverter and UPS.

Electronics Bazaar, South Asia’s No.1 Electronics B2B magazine