Makers of NiMH batteries & packs boost product performance

An Expert's View about Batteries, Accumulators in China

Last updated: 27 Jun 2012

R&D revolves around quality enhancements through feature upgrades and the use of better materials.

China suppliers of NiMH batteries and packs are gearing development efforts toward efficiency enhancements to stay ahead of the competition. Toward this end, makers are improving product features and adopting better materials.

Recent releases boast higher nominal capacity and discharge plateau, wider operating temperature, lower discharge rate, and longer charge retention and life span.

Under efforts to reduce self-discharge, many companies are launching ready-to-use cells. Unlike standard rechargeable variants that lose charge during storage, these precharged alternatives retain 75 percent capacity even after a year. In this category, 2,100mAh AA and 800mAh AAA batteries are mainstream.

R&D efforts also revolve around low-cost but high-stability components such as hydrogen storage alloys to boost battery cell performance. Specifically, companies are aiming for elevated storage capacity of electrochemical hydrogen in a wider operating temperature range. This will enable the alloy to achieve steady subdecompression for hydrogen anodic polarization at -20 to 60 C.

Makers are likewise emphasizing stronger antioxidant ability, lower reaction resistance, larger diffusion rate, chemical stability in alkaline electrolyte solution, efficient discharge, and good electrical and thermal conductivity. Most enterprises turn to the MmNi5 family of alloys, with misch metal accounting for 33 percent of the weight.

More forthcoming NiMH batteries are expected to use high-performance hydrogen storage alloys. Suppliers are also eyeing the development of low-cobalt and quasi-rapid cooling variants of the input.

China is one of the largest manufacturing hubs for NiMH batteries and packs worldwide. Despite intense competition from Japan and the dominance of lithium types, the line is projected to experience approximately 10 percent annual growth by year-end.

The battery packs segment alone is forecast to reach 463 million in total suppliersannual output at $559 million, with exports hitting 333 million units.

Although still beset with issues regarding charge efficiency, cell density and leakage, NiMH batteries boast built-in overcharge protection and self-recovery from overdischarge. They have greater capacity, long life span and light weight. Besides the absence of memory effect, products are 30 percent denser and more environment-friendly than NiCd counterparts.

To boost sales, suppliers of NiMH batteries and packs are planning to increase output. At present, the latter category shares about 20 percent of the industry's total yield. Major, midsize and small companies churn out 10 million, 3 million and 1 million units a month. Export-bound releases comply with RoHS, CE, UL, FCC and SASO requirements.

More makers are turning to "green" applications such as electric vehicles and bicycles, which are gaining popularity.

NiMH battery & pack selection

China manufacturers offer A, AA, AAA, C, D, SC and F batteries. The first four, which typically support 1.2V, are mainstream. For packs, enterprises can customize on request.
The products' wide application base covers consumer electronics to industrial equipment. Most are suitable for two-way radios, mobile phones, electric toys, power tools, emergency lighting, robots, backup storage appliances, guidance lights, EVs and drilling.

The nominal capacity for AA variants ranges from 1,600, 1,800, 2,000, 2,100, 2,300, 2,500, 2,600 to 2,700mAh, with the last being the highest in the market to date.

Toptech Battery (HK) Ltd's model of this type boasts low self-discharge, good storage performance and long life span.

AAA versions come in 650, 700, 800, 900 and 1,000mAh. Shenzhen Grepow Battery Co. Ltd said the last two are popular for their elevated capacity. These products are suitable for digital cameras, flashlights, radios, remote controls, and MP3 and portable CD players.

C and D types support 4,000 and 5,000mAh, and 9,000 and 10,000mAh, respectively.

Across the different variants, the standard charging time is 16hr. Products, however, boast quick-charge capability and can withstand high discharge rate up to 3C. They feature -20 to 50 C operating temperature.

For packs, makers are working more closely with customers to roll out models that best suit their requirements.

About 70 percent of NiMH batteries from China suppliers are used in battery packs. Such releases are smaller and lighter than lead-acid batteries, rendering them suitable for EVs and e-bikes. They boast high capacity and long life span.

Most players offer D types with 8,000, 9,000 and 10,000mAh capacity and 1.2V.

Meanwhile, 7,800, 8,800 and 12,500mAh batteries and packs with 24 and 36V are targeted at e-bikes and -scooters, electric golf cars and wheelchairs.

As for cells, players offer SC versions with 1,300, 1,500 or 1,800mAh. There are 2/3AAA with 300 and 350mAh, 2/3AA with 600 and 700mAh, and 2/3A with 1,200 and 1,300mAh. Some carry 4/5A with 1,800 and 2,000mAh, and A in 2,800mAh capacity. Further options include 4,000 and 1,200mAh 18,670HA.

To ensure consistent battery performance, makers are adopting wet pasting. Although costlier than the dry method, the former is widely used in electrode manufacturing because it is able to maintain a narrow performance variation.

The chief inputs are nickel foam and hydrogen storage alloys for the anode and cathode, respectively. The separator is likewise important.

The first, which is the standard anode requirement, is a three-dimensional network of high-purity nickel materials, with total impurities at 0.000001.

The length of each rolled strip varies from 150 to 300m, the width 100 to 1,000mm and thickness 1 to 3mm. The surface density is between 250 and 600g/sqm.

The separator is made of hydrophilic-treated nonwoven nylon or PP fabrics, and is placed closely between the positive and negative electrodes to reduce internal resistance and improve capacity and energy. NiMH battery separator requires good electrical insulation, temperature ionic conductivity, uniform porosity, mechanical strength, resistance to strong alkali and electrochemical stability. Most companies import the input from Germany, the UK and the US because local makers still face mass production difficulties.

With the cost of materials continuing to surge, enterprises such as Naccon Power Technology Co. Ltd and Shenzhen Grepow forecast an upward adjustment of 5 to 20 percent in coming months.

Hong Kong: NiMH batteries & packs feature enhanced capacity

Hong Kong makers of NiMH batteries are improving efficiency via increased product capacity. The latest releases include AA and AAA types with 2,900 and 1,100mAh capacity, respectively. Manufacturers offer C models with 5,000mAh and D versions with 10,000mAh. Buyers will also find 9V 250mAh batteries, and releases in other commercial and cylindrical sizes.

Companies are likewise introducing ready-to-use NiMH batteries that come with 2,300mAh for AA and 800mAh capacity for AAA. International standards and requirements, particularly in North America and the EU, are emphasized. The majority of manufacturers can provide safety approval certificate.

To meet clients' requirements, NiMH specialists are customizing packs based on size, power and price. For special features such as high-temperature tolerance, most Hong Kong suppliers have experienced R&D teams that can develop suitable products.

NiMH is currently the most widely available rechargeable battery type and is expected to remain so in the months ahead. The chemistry is used in remote-controlled toys, telecom devices and other electronics products. But to prepare for future trends and ensure strong sales, Hong Kong suppliers continue to pursue R&D in other battery technologies. In fact, some have introduced NiZn variants for both consumer and commercial applications. These feature a higher voltage, yet are lighter in weight, smaller in size and have lower internal impedance than NiMH. They are fully recyclable, unlike metal hydrides.

ATC EnergyTech Corp. Ltd, which has more than 60 years of experience in the line, is offering AA, AAA, C, D and 9V versions. Aside from 2,700mAh AA and 900mAh AAA models, the maker has ready-to-use series with a low self-discharge rate.

BetterPower HK Holding Ltd carries in its catalog 2,300mAh ready-to-use and 2,600mAh rechargeable AA NiMH batteries.

Vapex Technology Ltd concentrates on RC battery packs and large-capacity, high-rate rechargeable and ready-to-use NiMH versions. The company has introduced its easy-drain and fast-charging 2,900mAh AA, 1,100mAh AAA and 10,000mAh D models.

Read the full report on NiMH batteries at our import export business. Globalsources is a leading B2B marketplace and a primary facilitator of trade with China manufacturers and India suppliers, providing essential sourcing information to volume buyers through our e-magazines and trade shows.

Posted: 21 September 2011, last updated 27 June 2012

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