Power Electronics

Battery Addresses Back-up Power Requirements in PCs

NEC is developing a high-power organic radical battery (ORB) to protect IT equipment such as desktop PCs from losing data during power supply interruption. The film packed ORB demonstrates a maximum power of 35 W and its four series connected cells are capable of driving a 140-W class desktop PC in the event of power supply interruption. This prototype features a capacity of 100 mAh, a volumetric energy density of 38.1 Wh/L and a gravimetric energy density of 16.4 Wh/kg. The unit measures 55 mm × 43 mm × 4 mm, not including the external seal.

This technology is beneficial not only as an emergency power source for commercial computers and IT equipment, but also for a variety of equipment such as electrical household appliances.

ORB is a new class of rechargeable battery being uniquely developed by NEC, which uses the electrochemical reaction of organic radical compounds. This technology was initially proposed by NEC in 2001. To date, NEC has succeeded in synthesizing a polyradical of the modified PTMA, or "2,2,6,6-tetramethylpiperidinoxy-4-yl methacrylate," with excellent durability. Due to the high reactivity and reversibility of the radical reaction, the organic radical battery demonstrates extremely high power density and good cycleability, making it suitable for a range of next-generation applications.

A built-in ORB requires no energy conversions from ac-dc, or dc-ac. As a result, it realizes protection of equipment from power failure with no loss of energy. Environmentally friendly, the ORB consists of organic polymer, which contains no harmful heavy metals, such as Hg, Pb or Cd (materials found in existing battery chemistries). ORB has been confirmed to be inflammable and nonexplosive, making it extremely safe.

NEC has demonstrated the use of the ORB as an emergency power source for NEC's typical desktop PC, which consumes on average 96 W with a maximum power consumption of 228 W. In general, data backup of a PC takes several tens of seconds. Therefore, the battery only has to drive the PC for a short time during power failure to enable data backup. For example, 1.7 Wh of energy is required to drive a 100-W class PC for 60 seconds.

Conventional batteries comprised of Li-ion and Ni-MH cells are typically designed to have a cell capacity of 50 Wh or more to deliver the required power level (100 W). Consequently, it is considered uneconomical to use Li-ion or Ni-MH cells for PC data backup, as larger sized batteries are quite costly. On the contrary, a high-power ORB with a small capacity of 1 Wh is capable of discharging 100 W.

The four series connected cells are connected to the power unit of the desktop PC. When a power failure, blackout or voltage drop (of 20%) occurs, an off signal travels through the retention circuit, and the pulse generator starts the data back-up process and shutdown of the computer. During this period, the ORB supplies power to the PC. The cells with a total weight of 88 g can be easily mounted in most desktop PCs.

This research was carried out as part of a project to develop a high-power density organic radical battery for data-backup supported by the New Energy and Industrial Technology Development Organization (NEDO). NEC will continue to refine the technology from this point on, and research the market for this kind of battery toward possible commercialization. If a viable market exists, NEC hopes to create a business plan within two to three years toward commercialization of the battery.

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