SMF batteries: What’s new this summer season?

The perception about batteries is changing fast, especially with industrial users realising that a battery is a critical link to ensure backup power. Today, sealed maintenance free (SMF) batteries are the most popular technology used in a host of applications—from small UPS systems to large systems deployed in huge industrial plants. SMF batteries do not need maintenance and are pollution free. They, therefore, comply with the expectations of those customers that need to install batteries which require minimal or no maintenance, while being clean and ‘green’. The switchover to SMF batteries is also due to their lower price.

By Srabani Sen

Currently, this technology is widely used in telecommunications and in the power sector, and to some extent in the railways. Of late, the solar power industry has also offered good scope.

“Nowadays, customers are becoming more aware and don’t mind spending a few hundred rupees more for SMF batteries. They know about the disadvantages and hazards of lead acid batteries. The lead acid battery market size is reducing day by day, giving way to the SMF market,” says Venkat Rajaraman, CEO, Su-Kam Power Systems Ltd.

New types of SMF batteries in the market

SMF VRLA batteries are far superior to the conventional batteries. Their plates are made of lead calcium, which offer a longer life and higer efficiency due to low self discharge. SMF batteries are also environment friendly, require less space and can be used in any position.

If we go by the rated capacity, SMF VRLA batteries broadly fall into three segments—small: 3 to 17 Ah; medium: 26 to 200 Ah; and large single cells: 2V 100 Ah to 2V 3000 Ah. According to Rajaraman, the different types of SMF VRLA batteries that are currently available in the market are in the ranges of 50AH, 70AH, 90AH, 100AH, 120AH, 135AH, 150AH, 165AH, 180AH and 200AH.

Currently, two new types have entered the Indian battery market—absorbed glass mat (AGM) batteries and gel (or gel cell) batteries. These are often colloquially called sealed lead acid batteries, but they always include a safety pressure relief valve. As opposed to vented (also called flooded) batteries, a VRLA battery’s electrolyte does not spill if it is inverted. VRLA batteries also use much less electrolyte (battery acid) than traditional lead acid batteries. According to Manoj Pawar, regional manager, sales, Evolute, high rate discharge batteries are also much in demand. “We offer all the new types of SMF batteries including AGM, gel type, lead calcium (deep cycle) and high rate discharge batteries,” he says.

Anil Joshi, general manager, projects, Artheon Electronics, says that the fastest moving batteries in the market are SMF batteries with AGM separators, gel batteries, pure lead tin (PLT) batteries, traction batteries, batteries for e-bikes, generator starting batteries, solar lantern batteries, emergency lighting batteries and batteries for the telecom sector.

While Amptek offers improved SMF industrial batteries, and SMF bike and motor cycle batteries with AGM technology, Regnant offers deep cycle batteries that give 600 cycles at 75 per cent depth of discharge (DOD) or 700 cycles at 50 per cent DOD. “According to Japanese JIS standards, for normal SMF VRLA batteries, the recommended DOD for 500 cycles of charging/discharging is 50 per cent, which means that effectively only 50 per cent of the available capacity will be used. However, due to several reasons, especially in areas with poor power availability or those dependent on solar power, it is not always possible to achieve this. Therefore, for these applications, deep cycle batteries are ideal,” explains Praveen Kumar Sood, chairman, Regnant Energy Solutions.

Computech Systems is all set to launch deep cycle batteries. “Deep cycle batteries are designed to be discharged by as much as 80 per cent, time after time, and have much thicker plates. The major difference between a deep cycle battery and others is that the plates are made of solid grid and highest purity lead. Although these can be cycled down to 20 per cent discharge, the best way to get the optimum lifespan for the cost is to keep the average cycle at about 50 per cent discharge,” informs Vikas Aggarwal, CEO, Computech Systems. The company uses a Malaysian facility to manufacture its products under the brand name ipower.

About 70 per cent of Computech’s ipower SMF batteries cater to the UPS market. It also offers SMF batteries for electronic weighing machines, e-bikes, telecommunication equipment, solar panels, medical instruments, emergency lights, solar lanterns and CFL inverters. These ipower batteries comply to Japanese international quality standards, which is acceptable by the Indian government. “Our batteries has gone through all tests as per Japanese international standard in a government recognised test lab at ETDC, Mohali. We also have inhouse quality control and offer high quality products consistently,” says Aggarwal.

“Due to the growing demand from portable LED equipment manufacturers, we also offer a more cost effective 4V 4.5 Ah model. When the forward voltage drop of major white light LED emitters is in the region of 3.2-3.5V, with a simple constant current driver, you can efficiently power these with 4V SMF VRLA batteries instead of 6V. In the case of the latter, you will drop the additional power using a resistor, which is a total loss,” explains Sood of Regnant.

Says Biju Bruno, managing director, Greenvision Technologies Pvt Ltd, “We are working on a deep cycle design that would perform better in the extreme conditions faced in India. The product will be ready for launch in November 2010. We also have a model SPG 12-9 which is specifically meant for solar lamps and CFL UPS applications, and has a much better life than the conventional 7Ah batteries.”

Innovations in SMF batteries

In the age of innovation, the battery industry has not been left behind. “Keeping up with the demands of customers, SMF batteries are now designed to provide outstanding performance to withstand overcharge, over discharge, and to resist vibration and shock. Compact in size, these batteries save installation space, while providing full and reliable power. The use of special sealing epoxies and techniques assures users that the SMF VRLA battery has exceptional leak resistance, and can be used in any position,” explains Kapil Sood.

The latest innovation in this sector seems to be the deep cycle batteries. “Deep cycle batteries are based on 4BS technology and can be easily charged even after deep discharging. The entire charging process is also faster compared to a normal SMF VRLA battery of the same capacity,” says Sood.

Another innovation, as Sood points out, are the slim low height and narrow width front terminal batteries. “With 48.26 cm and 58.42 cm wide industry standard panels, in which battery banks are installed, we have made available slim low height and narrow width front terminal batteries which make maintenance as well as staking very user friendly, requiring less floor space. These are good for telecom station microwave towers or other places where office space is less. Power generating and distribution centres, railways, solar/wind power storage stations, etc use these batteries. Also, for proliferation of portable LED based solutions that require rechargeable batteries, we offer 4V batteries from 0.7 to 4.5 Ah,” adds Sood.

“AGM is an advanced technology used in SMF batteries that eliminates water loss. Once the battery is filled with acid, the battery is permanently sealed and there is no need to top it with water or check the acid level,” says Kapil Sood, CEO, Amptek Batteries.

“In batteries using AGM technology, electrolyte is absorbed into a mat of fine glass fibres. The plates in an AGM battery may be flat like a wet cell lead acid battery in a rectangular case,” explains Aggarwal.

In cylindrical AGMs, the plates are thin and wound into spirals, like most consumer disposable and rechargeable cells. The spiral construction allows purer lead in the plates, since the plate no longer needs to support its own weight as in traditional cells. The specific power of these batteries is very good and they can be charged and discharged quite rapidly. However, their specific energy tends to be lower than the traditional flooded batteries.

Another advancement is to add gel in batteries to improve the water retention during the charging and discharging recombination cycle. This improves the heat characteristics of the battery, as it is also one of the reasons for premature failure of batteries in India due to our climatic conditions and usage patterns, wherein proper ventilation is not provided at the place where batteries are installed making them vulnerable to high operating temperatures. This results in obtaining a lower capacity, a less number of charging/discharging cycles, or both. We have models that combine the benefits of both deep cycle and gel technology in order to give our customers the ultimate deep cycle gel SMF VRLA battery,” says Sood.

In a gel battery, sulphuric acid is mixed with silica fumes, which makes the resulting mass gel light and immobile. Unlike a flooded wet cell lead acid battery, these batteries do not need to be kept upright. Gel batteries reduce the electrolyte evaporation and spillage common in wet cell batteries, and boast greater resistance to extreme temperatures, shock and vibration. Chemically, they are the same as wet batteries except that the antimony in the lead plates is replaced by calcium.

Another latest technologies being used is expanded grid technology, by which thinner grids can be obtained to hold more active material. This increases the energy density of the batteries by reducing the lead required and thus reduces the cost. Many manufacturers are trying to switch over to it.

Says Joshi, “Nowadays batteries are made for specific products, usage or applications like e-bikes, generators, solar applications, etc. This is done by closely monitoring chemical compositions and charging techniques. Manufacturers are spending mainly on R&D to find the right chemical composition and charging technique.”

Rajaraman points out some technological changes in batteries. Some of these are the radial grid design to enhance the performance of high rate discharge; usage of thicker grids and corrosion resistant alloys for longer life; innovative formulated paste for deep cycle applications; and low gas emitting alloys (Pb-Ca-Sn-Al).

“SMF VRLA batteries have very low permeability, a low resistance current path and fast recharge capability,” says Rajesh Gupta, director, Okaya Power. “We use inter cell welding of the inner cell, which provides a very low resistance current path. We also use an extra thick special alloy for very long life and to prevent water loss,” he adds.

“There is a trend towards using better methods to chemically process the battery (to prevent electrolyte loss), purer lead (to prevent plate corrosion), newer technologies in the charging equipment (to improve battery life), and thicker plates (to decrease charging time),” says Aditya Arora, marketing head, Base Corporation.

Advances are also taking place in reducing corrosion and improving battery life through various combinations of the plate paste mix. The process of battery charging is being experimented with, with the trial of different techniques including the use of fuzzy logic.

“SMF batteries were earlier available only for C20 discharge rate. However, these batteries are now being designed for C10 as well as C5 discharge rate. Manufacturers worldwide are trying various constituents to make lead acid batteries much lighter and durable. They are using lead acid batteries with electrodes modified by addition of calcium for low maintenance, low overcharging, low self discharge and longer life,” adds Pawar.

Power saving features

Due to its construction, SMF VRLA batteries can, to some extent, save power. “Because of the use of lead calcium alloy and highly purity materials, these batteries can be stored for long periods of time without recharge at short intervals, thus saving power,” says Kapil Sood. Amptek batteries have exceptional deep discharge recovery and charge acceptance, which allows the battery to get charged very quickly even after deep or prolonged discharge.

Adds Rajaraman, “Quick charge capability, and less Ah input with respect to output when compared to flooded batteries, also helps to save power.”

According to Joshi, normally, discharge is due to usage or self discharge. While usage related leakages are controlled by having the right electronic components in the circuit, self discharge can be controlled by providing the right environment, i.e., avoiding extreme temperatures as well as by maintaining the purity of metals to reduce internal resistance. This also helps in saving power.

Pawar points out that since batteries are being designed for faster rate of discharge, the derating factor has come down considerably. It has also enhanced efficiency of the batteries, leading to saving of power.

Periodical maintenance required

SMF batteries are user friendly as they need minimal maintenance and there is no harmful acid gas evolution. However, periodic checking of the terminal bolts, open circuit voltage and internal resistance once in six months is recommended. Says Pawar, “SMF batteries can be charged using simple power supplies that can be linear power supplies and SMPS. There is no question of overcharging if charging voltage is set within permissible limit as the current acceptance of battery goes down with charging. This is definitely a user friendly feature.”

“Routine maintenance in terms of checking of charging parameters, voltage reading, etc, needs to be done for VRLA batteries also. They are sensitive to charging parameters and depth of discharge, and if proper care and maintenance in terms of sizing and running the battery is not taken, there is a chance of failure,” says Tarit Kumar Roy, general manager, institutional UPS—telecom, railways and solar, Exide Industries.

Joshi explains, “One cannot rule out a few guidelines for a healthy battery life. The battery should be kept in a dust free environment that is not too warm, avoiding direct sunlight. It should be regularly cleaned and proper charging should be ensured. One should also ensure equalisation, that is, in case of a battery bank, all batteries should have equal voltage. In case of a battery bank, one should not use old and new batteries.”

Sood of Regnant says that if proper recommended charging and discharging conditions are met along with operating temperature conditions, then batteries can last anywhere from 3 to 5 years, which makes them a very economical and viable choice for customers.

Buying tips

Long life, warranty support, better prices are some of the requirements of the buyers. There is a rising requirement for gel battery for solar and LED based lighting. Also the market for deep discharged VRLA batteries is picking up.

However, if no effort goes into selecting the right solutions for backup power storage, it can lead to a situation where an office’s entire operations come to a standstill because of the unavailability of power.

Lack of awareness among consumers about the importance of the quality of batteries is one reason why most manufacturers and marketers do not bother about setting international standards for their products, introducing superior technologies or offering quality service. A battery is a consumable and has a definite service life, which can be maximised by users, provided they know how to choose the right category, select the right features, ensure proper installation and follow ideal usage patterns.

“Customers should be informed about what batteries are being supplied and ask questions about the company, brand, the support network, replacement policies, quality, life of the battery, etc. It is also important that they check on the quality of the UPS system or other equipment that they will use with the battery. In most cases, batteries are abused rather than used, simply because the solutions provider is unaware of or ignores the basic precautions to be taken during installation,” informs Bruno.

Joshi suggests that buyers should select the right battery for specific applications and never compromise on quality because of price. “Always inform the battery company about the application in order to select the right battery. Also, avoid undersizing or oversizing the battery for a certain product. In short, buyers should look for reliability, good quality, timely service, technical support, lower cost of operation and long trouble free battery life.”

A buyer should be able to distinguish between a battery using pure lead and one with recycled lead. “In case, a vendor is offering a battery at a very cheap rate, it means that the battery has recycled lead. Such a battery may initially offer good results but will eventually fail in a couple of months,” adds Joshi. Bruno, therefore, suggests that a buyer should purchase only from a known and established vendor and do a thorough background check of the company.

“Unscrupulous manufacturers and grey market operators can offer a cheaper product, which will not yield proper ROI on the investment. Such batteries usually have a high internal resistance resulting in an actual realised capacity that’s much lower than what is claimed, and even self discharge is unusually high,” warns Sood.

Adds Aggarwal, “Buyers should buy products that go through genuine quality tests. For example, all our products have test reports from government approved independent test lab. Buyers should also check the background of the company. Computech Systems has credibility in the battery market with its experience of 15 years.”

“For consumers, it is advised to buy batteries from authorised dealers, thus ensuring that they are buying original brands. Cheap batteries from unreliable sources could be found underperforming and may also be hazardous. For OEMs, it is advised to evaluate batteries properly before approving any particular brand or buying batteries from new sources. OEMs can be attracted by aggressive prices and terms but finally a field problem can cause much bigger consequential loss as compared to minute difference in price and terms,” concludes Pawar.

How safe are SMF batteries? Since VRLA batteries are sealed, there is no leakage of electrolyte or gases. Compared to traditional batteries, these models can be broken down in organised recycling plants under much safer environmental conditions. Almost all the materials are recyclable, hence their disposal is environment friendly. The materials that can be recycled include lead, electrolyte, plastic, steel and copper (not in automotive batteries). However, lead being a hazardous material, proper care needs to be taken by the user for its disposal. Scrap batteries should be given only to government authorised smelters with the proper infrastructure to recycle the lead. The government has mandated that used batteries have to be purchased back by the seller.

Major application areas Telecom systems & equipment Inverters UPS systems Emergency lights Big weighing machines Solar power systems E-bikes Motorcycles Medical instruments Portable powered tools Powered toys Lighting equipment Electric equipment and telemetry equipment Lawn movers, vacuum cleaners and washing machines Consumer electronics Fire alarm and security systems Portable personal computers Garden lighting Portable power stations

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