NiMH batteries/packs

	China suppliers are making power-packed, safer-to-use and greener NiMH batteries
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New materials and components enhance the product's power efficiency, reduce the self-discharge rate and extend its life span.

China suppliers are making power-packed, safer-to-use and “greener” NiMH batteries. By choosing alternative electrodes, electrolytes and additives, companies have increased the cell’s nominal capacity, reduced its self-discharge rate, broadened operating temperature and extended the life span.

NiMH cells are currently the most viable alternative to NiCd units. They do not contain cadmium, which is potentially harmful to the environment, and have less memory effect. Although they have high energy density, standard units can only retain 20 percent of their charge after a year of storage. On new models, makers have raised the nominal capacity by as much as 90 percent and the recycle life by 1,000 times.

To optimize the discharge rate, suppliers are adopting cobalt hydroxide colloids. By adding magnesium to the cathode material, some have come up with the AB3 alloy, which is less volatile than the AB5 staple. A number of companies use nickel-plated punched steel in the wet-pasting process, a control method for loading electrodes, to stabilize the battery chemistry and enhance performance. Others have honed their customization skills for environment-friendly models.

China suppliers claim that their NiMH batteries have a higher price-performance ratio than those made in Japan, which are 25 percent more expensive. They hope to keep the edge by using cost-efficient components without compromising product quality.

Standard quotes for China-made AAAAs and AAAs are $0.50 per unit. For AA and SC sizes, the range is between $0.50 and $2.20, and D and F models are $2.20 to $12. Nickel, cobalt, steel and copper account for 70 percent of product cost.

Nickel costs fell about 65 percent in 2008 and stood at $9,300 per ton in March 2009. In response, battery makers have lowered their prices by as much as 40 percent.

Electrodes and housing materials are largely sourced locally but the more-crucial separator is usually imported from Japan and Germany. High-end models from big players such as BetterPower Battery Co. Ltd have electrolytes from France or the US.

To ensure the integrity of the electrode powder used in their products, China makers set the humidity in their facilities to 60 percent to prevent electrolytes from absorbing carbon dioxide and developing impurities. The weight of each electrode slice is also tested for accuracy and consistency.

New models come in A, AA, AAA, AAAA, SC, C, D and F form factors. These are marketed as individual cells or battery packs, usually under OEM or ODM. The typical applications are hybrid electric vehicles or HEVs, power tools, digital cameras, A/V equipment, small home appliances, communication devices, laptops and electronic toys. The mainstream types are AA rated at 1,500 to 2,600mAh and AAA with a 600 to 1,000mAh capacity.