The latest solar batteries have become smarter and more efficient

With continual technological advances, solar batteries have become more efficient, offering longer hours of operation and ultra low maintenance.

By Kartiki Negi

Thursday, October 30, 2014:  Solar batteries are the core component of both off-grid and grid-connected solar applications. Also called deep cycle batteries, solar batteries vary considerably from the regular type of batteries. Off-grid photovoltaic (PV) solar power equipment requires a battery to store the energy accumulated during the sunny hours, for use at night. These solar batteries store power from the main source (sun), unlike the conventional batteries where the power source comes from the mains (electricity). In most applications, lead acid batteries are preferred as these are maintenance-free and do not emit any harmful gases during the charging process.

Solar batteries are widely used in solar home lighting systems and solar streetlight systems. They are also used for rural electrification through micro grids. Solar lanterns use small capacity batteries, ranging from 4.5Ah to 7Ah, mainly for emergency lights in rural areas, and in off-grid or hybrid solar systems at homes, remote offices and other sites with no grid connectivity.

What’s available in the market

Solar batteries are of three types—lead acid solar batteries, sealed maintenance-free valve regulated lead acid (SMF VRLA) batteries and deep cycle solar batteries. Manufacturers are continuously trying to come up with innovative technology in a bid to offer batteries that are more rugged, affordable and long lasting, even in extreme conditions.

“Pressure die cast batteries offer the most superior technology, as of now. Base Batteries is presently working on gel batteries, which are expected to be the next revolution in the tubular technology space,” says Aditya Arora, COO, Base Batteries Ltd.

Okaya Power Ltd offers advanced tubular solar batteries of 20Ah, 40Ah, 75Ah, 100Ah, 120Ah, 150Ah and 200Ah capacities at C10, which require extremely low maintenance. They come with high ampere-hour and watt-hour efficiency and a low self-discharge rate. Key applications of these batteries are in solar photovoltaic power plants, solar street lights, solar lanterns and traffic signals. “Our batteries come with three and five-year warranties and are tested and certified by the Solar Energy Centre, MNRE,” says Rajesh Gupta, director, Okaya Power Ltd.

Base Batteries Ltd offers its Radiance series of PDC (pressure die cast) tubular solar batteries that are used in off-grid solar applications. The series has been approved by the Ministry of New and Renewable Energy (MNRE) and comes with a five-year warranty.

“Our solar products range from 20Ah to 150Ah. We use pressure die cast technology, instead of gravity casting or slurry casting. Lead is injected into the mould at 100 Bar pressure, eliminating any scope for air bubbles in the grid, resulting in consistent and reliable performance. The machines used for this process are of military grade, which only a few manufacturers use,” says Aditya Arora.

Southern Batteries’ existing Hi-Power solar series of tubular batteries comes with several features. Its 2V cells are designed to suit the system’s configuration requirements, where the tubular cell construction is in rigid hard rubber containers. It comes with low antimonial lead alloy grids, which achieve a low topping up frequency of once a year. It also provides transparent sealed level indicators that give the topping up requirement, and micro porous ceramic vent plugs that minimise topping up frequency.

Luminous’ solar flooded tubular monobloc batteries are designed to offer reliable and consistent power for solar requirements, but with low maintenance. These batteries can be subject to deep cycle applications yet need minimum maintenance in rural and power deficit areas. The monobloc batteries have the capacity to withstand partial state of charge (PSOC) operation. They are available in 12V from 20Ah to 200Ah @ C10 at 27°C to 1.80 vpc.

MNRE-approved batteries are designed to give a long life in cyclic operations. They operate for extremely long intervals before they need to be topped up, and require virtually zero maintenance. These batteries can be adapted to use auto-fill systems and air agitation systems for faster charging and to avoid acid stratification in standby cells. For outdoor applications, these batteries come in IP55 enclosures.

Artheon Electronics Ltd offers solar tubular batteries that are appropriate for use in areas that suffer from frequent power cuts. The product comes with extra heavy duty plates to ensure durability, resistance to grid corrosion and inbuilt margins for high ambient temperature and vibrations. The battery is free from micro shorts and plate shedding, and can hold active material. It also comes with a PE envelope separator that eliminates infant failures, low self-discharge for longer shelf life, and a high efficiency grid design for enhanced performance. The battery is available in 20Ah, 40Ah, 75Ah, 100Ah, 150Ah, 165Ah and 200Ah. The product range conforms to all quality standards and offers a 24-month warranty with after sales services.

Buying tips

When choosing a solar battery, a few points need to be kept in mind. Otherwise, one might end up buying the wrong type of battery, which could hamper its performance as well as efficiency. Deep cycle capability, long cyclic life and the reputation of the brand for its good service network are some of the factors to be kept in mind while purchasing a solar battery.

Power requirement: Before zeroing in on a solar battery, you should first assess your power requirement. It is advisable that any battery chosen for storing power must be capable of sustaining a charge at least five times the amount of the daily usage. If one intends to use quite a lot of the solar energy collected through the day, you will need a high performance battery. So, the ability of the battery to operate properly in partial state of charge is critical. For Indian conditions, certain types of lead acid batteries are not suited for solar photovoltaic (SPV) operations and may end up with premature failures.

Size of a battery: This is another factor to be looked at. It is necessary to have a system where the battery size gives you enough stored electricity. In order to achieve this, one has to look at the daily usage in Kw hours, how convenient the backup system is, the time that the system is expected to cope without sunshine, etc. The maximum problems are encountered due to undercharging of the battery, which also reduces its lifecycle.

Battery measurements: This is a vital factor to be kept in mind. A 100 amphour battery, in theory, can supply a current of 1 amp for 100 hours before becoming fully discharged. Thus, if a battery has a capacity of 100 amphours (C10), it will supply 100 amphours when discharged over a 10 hour period.

Rating: It is very important to select a solar battery with the right rating. There are several test reports available from the MNRE, the Central Power Research Institute (CPRI), etc, which show the capacity and other parameters of the battery. Batteries should be tested to comply with the Bureau of Indian Standards (BIS) at these labs.

Maintenance: After sales service is an important factor due to the remote locations these batteries are usually used in. Therefore, maintenance requirements of the batteries should be considered before buying.

Location: Customers should also ensure that the solar power system is installed at a location that receives abundant sunlight, in order to be able to generate enough power from the solar panels, which need to be stored in the solar batteries.

Warranty: Solar batteries come with extended warranties of up to 60 months. The cost of a longer warranty period is higher. Hence, customers should be clear about the warranty required by them and the corresponding cost.

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