AA-size cells

Thcse capacity values are obtained at the initial discharge of AA-size cells. 

The connection of AA-size cells in parallel can replace larger cells (e.g., D-size cells). Four AA cells fit into a D-size can, and six AA-cells are in equivalent weight to a D-cell [27]. The utilization of the Mn02 cathode is considerably improved because the cathode thickness is only 2 mm in a AA cell, but 5 mm in a D-cell. The internal resistance is also lower by a factor of 4 to 6. Figure 11 depicts a 5 PxlO S bundle battery five AA cells in parallel = 1 bundle, 10 bundles in series make a (nominal) 12 V battery. It is used as the power source for a transmitter/receiver service. A typical load profile is 2 A for 1 min, 0.33 A for 9 min average load, 0.5 A per bundle or 0.1 A per cell service, about 15 h. Smaller bundle batteries (with 2x9 cells) are very suitable for notebook-computers 18 AA cells weight 0.36 kg, and the total initial capacity is 32 Wh. 

We have developed a prototype AA-size cell which consists of an amorphous (a-)... 

Nickel-melal hydride cells can be discharged at the 2 C rate (and in some cases at 4 C) and charged at 1 C. An AA-sized cell with a nominal capacity of over 1 Ah can thus be discharged at over 2 A and with a peak current of over 10 A. The energy density is highly dependent on rate, but for comparable conditions is 25% higher than an equivalent nickel-cadmium cell. Fig. 6.12 shows a comparison of the discharge characteristics of these two systems. 

RAM cells are manufactured and shipped charged and have an initial capacity of about 1.8 Ah for AA-sized cells discharged at 50 mA (in comparison with, say, 2 Ah for an equivalent primary cell). This capacity falls to 1 Ah after storage for 3 years at room temperature. At higher drains, the initial capacity drops to about 0.6 Ah at 400 mA (Fig. 6.14). Cells are designed to operate within a temperature range of 0-65°C. The higher internal resistance of RAM cells limits their maximum continuous output current and also their peak output currents in comparison both with primary cells and with nickel-cadmium and nickel-metal hydride secondary cells. A new cell will have an internal resistance of approximately 0.1 2, but this will rise to 0.25 2 with use. 

Molybdenum disulphide is another layered intercalation host, similar to titanium disulphide. This material occurs naturally and formed the basis of the positive electrode for the first high production cylindrical AA-sized cell, manufactured by Moli Energy Ltd in Canada in the 1980s. Cycle life of 100-300 was achieved in practical cells with average discharge voltages of 1.8 V for low rates, giving a theoretical density of approximately 300 Wh/kg. 

Fig. 7.27 Comparison of discharge behaviour of Li-LiMn306 AA-sized cells with nickel-cadmium and nickel-metal hydride cells. (By permission of Tadiran.)...

The annual production value of small, sealed nickel-cadmium cells is over 1.2 I09. However, environmental considerations relating to cadmium are necessitating changes in the fabrication techniques, as well as recovery of failed cells. Batteiy system designers are switching to nickel-metal hydride (MH) cells for some applications, typically in AA -size cells, to increase capacity in the same volume and avoid the use of cadmium. 

Since 1987 the development emphasis was shifted to the AA size cell which represents over 50 % of the consumer market. Figure 16 shows that the 1992 cell design has become very similar to the one of primary alkaline cells. Most noticeable is a simplification of the cell construction. Both mechanical cathode confinement and the complicated current collector design were abandoned [38]. 

Alkaline Primary Cells, Fig. 3 Discharge of the alkaline AA-size cell (MN1500) at three discharge rates. The sloping discharge is the characteristic of the alkaline Zn—Mn02 cell system (Courtesy of Duracell)... 

FIGURE 7.5 Typical discharge curves for primary battery systems. AA-size cells, approx. 20-mA discharge rate. f A-size battery. (h) ANSI 1604 battery 9-V, 250-tl discharge load. 

FIGURE 14.79 On-load voltage of Li/FeS2 AA-size cells. (Courtesy of Eveready Battery Co., Inc.)... 

Fig. 2. Overcharge characteristics of a Ni-MH AA-size cell during the 30th cycle (current 200 mA, temperature 25 C) (Kanda et ai. 1991).

AA-size cells constracted by Battery Technologies Inc. in the U.S. show very good endurance tests. These cells accumulate up to 400 cycles on the 24-Q test and up to 250 cycles on the 10-Q test. The Li-Mn02 cells developed by Sanyo Electric Co. in Japan are termed ML 2430 and ML 2016 with nominal capacity of 70 and 20 mA h, respectively. About 200 cycles are obtained at a capacity of 45 mA h. The flat-type battery ML 2430 with a nominal voltage of 3 V can operate over 3000 cycles at a low discharge capacity of 1 mA h. European efforts are also directed toward Li-Mn02 secondary batteries. Researches are developed by SAFT in France and Varta in Germary (see Table 11.7). 

A new AA-size Li/MogSg rechargeable cell has been developed to the prototype stage by Moli Energy Ltd. This cell can deliver about 2 W h of energy and is capable of a high-rate discharge up to about the 2C rate. This AA-size cell delivers 100 W h kg with a typical life of 200 cycles. 

Figure 4.1 Total world production of EMD and chemical manganese dioxide (CMD). Table 4.1 Capacity of primary AA-size cells.

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