Solar batteries: Rugged, long lasting & affordable

Solar batteries aren’t the regular type that you can pick up at your local dealer. Also called deep cycle batteries, they are very different from, say, the one that’s used in your car or inverter. Solar batteries are the core component of solar applications, both off-grid and grid connected. Although there are many companies offering branded and unbranded solar batteries, the question is whether the hype around is more of a marketing gimmick, or has the sector actually achieved technology improvements? Nina Benjamin Singh, director, Inphynyt Accumulators India Pvt Ltd, puts it this way, “Solar applications demand batteries that are capable of delivering an optimum performance at higher temperatures with deeper cycling and low maintenance. They also provide a higher cyclic life under partial state of charge (PSoC) conditions. Tubular plate technology, clubbed with gelled electrolytes, has proved to be the most robust and reliable. It is completely maintenance free and is suitable for all applications.”

By Sandhya Malhotra

Saturday, March 12 2011: High demand for solar batteries

The demand for solar batteries is growing at an accelerated rate in India. This is attributed to the Central government’s push for the usage of solar energy and solar products, especially under the Jawaharlal Nehru Solar Mission. Largely, the growth of solar batteries in India is driven by the persistent energy shortage in the country. Today, one-third of the population does not have access to grid electricity, and with an increased government focus on renewable energy and new incentive schemes for solar power plants, it would mean rapid market growth for solar batteries in the coming years.

MM Venkata Krishna, general manager, direct business, industrial batteries, Amara Raja Electronics Ltd, says, “We see the current solar battery market potential as being around Rs 1500 million. Moreover, with the launch of the Solar Mission, 8000 MW of off-grid solar power is expected to be added in the next 12 years. Hence, this will increase year-on-year at a rate of 40 per cent, pushing up solar battery demand.”

TERI’s ‘Lighting a billion lives (LaBL)’ campaign has not only increased demand for off-grid solar PV (SPV) systems, but has also triggered demand for solar batteries. “This is a big opportunity for battery players. We are planning to supply our solar batteries for the LaBL campaign,” says Sunil Bhatnagar, director, marketing, Artheon Electronics Ltd.

Apart from the Solar Mission, government subsidy and schemes have also added to the demand for solar batteries. “Indian Renewable Energy Development Agency (IREDA) provides revolving funds to financing and leasing companies offering affordable credit for the purchase of solar PV systems in India. Additional incentives include 80 per cent accelerated depreciation, lower import duties on raw materials, and excise duty exemptions on solar devices—all of which are fuelling the growth of solar batteries in the country,” says Biju Bruno, managing director, Greenvision Technologies.

SPV systems are an alternate source of energy in various segments including telecom, railways, captive power plants, power generation, traffic lights, rural electrification and defence. Moreover, the government is pushing telecom companies to convert diesel run telecom towers to solar power. “Although solar driven telecom services are in a nascent stage, there is bound to be an upsurge by the end of 2010, considering government initiatives in the form of subsidy for solar panels. We see the solar battery industry set to grow tremendously,” says Avnish Arora, vice president, HBL Power Systems Ltd.

According to Praveen Kumar Sood, chairman, Regnant Energy Solutions, “Off-grid SPV applications, such as solar lanterns, solar street lighting, home lighting systems and SPV pumps, are fuelling demand for solar batteries in India, and are being promoted on a very large scale all over the country.”

Types of solar batteries

The prime function of solar batteries is to store power generated from a power source (for example, solar panels) and discharge it when the power is required (through an inverter). Lead acid batteries are the most common in PV systems. There are many different sizes and designs of lead acid batteries, but the most important feature of the solar battery is that it is of the deep cycle type.

Lead acid batteries are available in wet cell (high maintenance) and sealed (no maintenance) versions. AGM and tubular gel are popular under maintenance free category, in which tubular gel batteries are designed to cater for deep cycle applications operated at higher ambient, hence, last a lot longer.

Commenting on how solar batteries are different from normal batteries, Praveen Sood says, “The raw materials required and the process of making a solar battery is quite similar to that of industrial batteries, with some variations for customisation. High purity lead and allied lead compounds, plastic containers, terminals, gel electrolytes and AGM separators are required for the manufacture of solar batteries.”

Deep cycle solar application batteries are used in renewable energy applications as these batteries typically feature thick plates with a high density active material. In a solar battery, thick battery plates allow for reserve energy to be stored deep within the battery plate, to be released during slow discharge. “The solar deep cycle battery uses a different chemistry for the plates’ active paste material. This chemistry allows for a much longer life in deep cycle applications with only a slight reduction in maximum power output,” says Nina Singh.

Bruno of Greenvision says, “Only rechargeable batteries are used for SPV applications. The choice of batteries is made on the basis of load duration and cost considerations. Alkaline and rechargeable batteries are most favoured with different chemistries such as Ni-Cd, Ni-MH, Ni-Fe, Li ion, Li polymer, LiFePo4 and Pb acid.”

“For many years, Indian buyers have been using flooded electrolyte type batteries, which require regular maintenance and are also not suitable for high temperatures frequently encountered in outdoor installations. But now, they are moving towards deep cycle gel based batteries which Regnant supplies. If properly used, such batteries can last for five to eight years without any maintenance,” says Praveen Sood.

Innovations in solar batteries

To make solar batteries more rugged, long lasting in extreme conditions and affordable, manufacturers have started focusing on technological advancements.

Says Biju Bruno, “Our solar tubular batteries are manufactured in Bengaluru, while the SMF batteries are made in China. Understanding the need of remote customers, we are improving our batteries by enhancing the efficiencies of the raw material used in different types of rechargeable batteries like g/Ah, reducing the internal resistance of the cell or battery, which can enable it to withstand high temperatures and humidity.”

Venkata Krishna adds, “We are trying to manufacture solar batteries that are lithium based. However, this is not viable at the moment.”

Explaining the new technology, Kapil Sood, CEO, Amptek Battery, says, “Though lead acid batteries are the cheapest among all kinds of rechargeable batteries, new innovations are taking place in lithium batteries for solar applications. The reason for this trend is simple—lithium is the lightest metal, which results in a high specific charge. For example, it takes 3.85g of lead to produce 1 amp for 1 hour, while it only takes 0.26g of lithium to produce the same. One type of lithium battery is only 2.5 mm. Lithium also produces a higher voltage and, therefore, a higher energy density. Lithium is even more ecofriendly than lead or cadmium. These characteristics seem to fit right in line with market trends and many solar battery manufacturers are considering the same.”

Nina Singh adds, “We will be rolling out our solar and regular range of batteries this month. On the basis of our constant research and development to develop a battery for solar applications, we have used special additives, superior alloy composition, a rugged grid design and unique desulphator technology, which has resulted in very longlasting and cost effective batteries. The battery plates are much thicker than those in conventional batteries. Moreover, to make our batteries hassle and maintenance free, we have added features like automatic water filling systems and automatic electrolyte LED indicators.”

Challenges buyers face

Biju Bruno points out, “One of the key challenges buyers face while purchasing batteries for solar applications is that most of the usage happens at remote and off-grid locations. Hence, the ability to get service at these locations becomes difficult.”

Vankata Krishna says, “The key challenge customers face while buying a solar battery lies in identifying the right technology for solar batteries; figuring out the best quality provider in the industry; and assessing how adequately the battery’s technology is conceived with benefits ranging from the warranty as payback period is higher for solar solutions.”

Avnish Arora, however, points out that battery charging is the key to ensure the required backup during non-sunny days as well. Praveen Sood says, “It is very important to integrate an appropriate electronic control circuitry matching the batteries’ characteristics in order to achieve the maximum life cycle, which most people in India unfortunately do not know about.”

Buying tips

By using solar power, the environment is free from CO2 pollution, which is generally a byproduct of conventional energy sources. Hence, the battery as a component of the solution should also be environmental friendly. Customers should consider environmental friendly solutions while selecting the product, says Venkata Krishna.

Praveen Sood says, “Before buying a solar battery, a customer must check the size of the battery bank by taking the help of technical experts—keeping in mind the likely load on a daily basis and the charging capability, since maximum problems are encountered due to undercharging of the battery, which also reduces its lifecycle.”

Kapil Sood adds, “Customers must decide on the correct capacity of the battery required as per the electric load and the geographic location. The latter is an important factor as the number of sunny and non-sunny days determines the Ah capacity of the battery. Therefore, buyers must always look for deep cycle versions, so that the batteries are able to recharge after deep discharge.”

“A key factor to consider while buying batteries for solar applications is the battery’s capability to manage a slow rate of discharge and its ability to recover from a state of full discharge. Don’t buy a battery as offered by your supplier, instead look for a battery that caters to all your needs,” concludes Nina Singh.

Products and their features:

Note: The names of the companies are in alphabetical order.

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