Latest rechargeable batteries offer increased density and longer life

Advances in technology have played a major role in reducing costs and in improving performance. However, manufacturers are still working towards increasing energy density.

By Kartiki Negi

Wednesday, March 12, 2014: Rechargeable batteries or battery packs are currently used in almost all industries including automation, medical electronics, weighing machines, lighting, handheld terminals, equipment, etc. With the increasing use of gadgets like laptops, iPods and smartphones, we are becoming even more reliant on rechargeable batteries, also called cylindrical cells.

LED lighting is also triggering a large demand for small battery-based battery packs. LED lights are used in torches, exit lights, solar lights, etc. Other important market drivers are instrumentation and medical devices.

What’s in demand

The common types of rechargeable batteries that dominate the market are nickel-cadmium (NiCd), nickel-metal hydride (NiMH), lithium-ion (Li-ion), lithium-polymer (Li-poly) and sealed maintenance-free lead acid batteries.Lithium iron phosphate(Li-Fe PO4) is the latest addition.

“LiFePO4 batteries have a nominal voltage of 3.2 V. However, they are not very widely used due to their high price. LiFePO4 batteries have several advanced features compared to other batteries but are yet to capture the market. First, they have a longer life with 1000 to 2000 charge/discharge cycles; SLA batteries only provide 300 cycles and Ni-MH batteries have 300 to 500 cycles,” says S S Kandhari, managing director, Kandhari Photo Electronics. Second, these batteries are lightweight when compared to other batteries, are safer as they never explode, and are much more stable at high temperatures.

NiZn batteries are an upgraded combination of NiMH, alkaline and NiCd batteries. A NiZn single cell is of 1.6 V and is environment friendly. This battery has the higher voltage of alkaline batteries, the high current discharge feature of NiCd batteries, and is pollution-free like NiMH batteries.

Boston Sonata’s Li-ion cell has 800 charge/discharge cycles, a voltage of 3.7 V, and a 4400 mAh capacity. It is also eco-friendly.

The latest in the market

Evolute Solutions launched a new series of LiFePO4 rechargeable batteries in December 2013.

A normal LiFePO4 battery is capable of being fast-charged at a rate of 3 C and fully charged in 20 minutes. The discharge rate can even go as high as 30 C. Sources at Evolute claim that the uniqueness of the product is that the battery management and protection circuit have been indigenously designed and developed by the company; hence, its LiFePO4 battery is safer compared to other available lithium battery options. “Our series is used in several fields including electric vehicles, energy storage systems, telecom and other applications, which need fast charging and high current discharges,” says Manoj Pawar, senior product manager, Evolute Solutions.

Kandhari Photo Electronics recently introduced a high capacity Samsung Li-ion cylindrical (18650 size) series of batteries/battery packs with an optional fuel gauge. The series caters to the requirements of segments like solar and LED lighting, handheld terminals, POS devices like ticketing machines, meter reading instruments, etc. It is also used in medical devices such as ECG machines and infusion pumps, in the defence sector, and in portable chargers for mobile phones, iPods, etc.

“We have been getting a good response from our customers in all the above fields. Our series is the most reliable high capacity battery among international brands, and has a very long and good track record as it is used by reputed laptop, power tool and search light brands,” says S S Kandhari.

Prime Products has also launched lithium-ion packs, which offer higher voltage compared to all other technologies (3.7 V vs 2 V or 1.2 V). As a result, fewer cells are required for any design. These feature higher energy density, which leads to smaller, more compact battery packs. “Lithium ion is a very attractive option for high discharge applications where lead acid batteries require larger size due to ‘derating’. It is also used in various lighting applications like solar lanterns and street lights. Medical electronics manufacturers are also now choosing lithium ion over lead acid,” says Tarun Desai, CEO, Prime Products.

Technological advances

The market for rechargeable batteries is consistently evolving. Technological breakthroughs have played a major role in reducing costs and improving performance. However, manufacturers are now working towards increasing energy density and ensuring longer battery life.

Manoj Pawar of Evolute Solutions says that though the company is coming out with the latest version of rechargeable batteries, it is continuously focusing on increasing the energy density and charge/discharge cyles of these batteries.

Kandhari Photo Electronics’ latest launch, the 18650 Li-ion cell, offers upgraded capacity. “Most of the companies manufacture 18650 Li-ion cells of up to 2200 mAh capacity but we offer a range covering 2600, 2800 and 3000 mAh,” says S S Kandhari. Besides, these Li-ion battery packs are assembled with a protection PCB for accurate charging and discharging cut-offs.

Says Tarun Desai, “We find energy density crossing new levels, as the technology advances. Earlier, 18650 lithium ion batteries used to be available with a capacity of up to 2400 mAh but today they are available in capacities of up to 2800 mAh and, maybe, we will soon get versions with even higher capacities. Also, these batteries used to be around six to seven times costlier than the lead acid batteries for the same capacity. Now, prices for lithium-ion have reduced. For small AH applications lithium-ion is more attractive than lead acid because cost per AH of lead acid for small AH is higher.”

“Unlike earlier, a customer today is more conscious about the environment and prefers environment friendly batteries. Hence, manufacturers are now looking at new technologies wherein they can provide the customer with the power they require in a much more compact form while also being environment friendly,” says Manoj Pawar.

Li-ion batteries have a high reliability factor, are economical and are considered the best option to change over from SLA batteries. They are more eco-friendly compared to SLA and NiCd batteries. Li-ion and Li-poly batteries are both lightweight, come in small sizes, and the battery packs come with proper, more accurate charge and discharge cut-offs.

Buying tips

Customers should be very careful while buying batteries as a wrong choice can lead to failure of the equipment. “A buyer should keep in mind that the battery is the heart of the equipment and, hence, one should not compromise on the quality for the sake of petty discounts,” says Manoj Pawar.

Reliable brands would be preferable, if you want a quality product. Buyers must also keep the environment in mind. “Customers must opt for environment friendly batteries such as Li-ion, Li-poly or LiFePO4. These batteries offer value for money,” says S S Kandhari.

Another factor that one must consider is the consistency in capacity, as it is very important for the batteries to work in series and in parallel combinations. One has to be careful while choosing because, for example, lithium batteries should be always used with battery protection circuits (BPC), which must be based on maximum charge and discharge requirements.

Customers should be wary about certain malpractices prevalent among some suppliers. Explains Tarun Desai, “These days, the AH per weight has increased with the advancement in technology in the sphere of lead acid batteries. Hence, more AH is packed into less weight. However, customers are often laying too much emphasis on the weight of the battery instead of the capacity. This has led to some suppliers increasing the weight by manipulating the material content, which impacts the life of the battery.”