Sanyo Electric Co., Ltd.

Akio Furukawa

Ikuo Yonezu

Shin Fujitani

Toshihiko Saito

Kenji Nasako

Takahiro Yonesaki

Takaaki Matsubayashi

Nobuyoshi Nishizawa

Masaru Tsutsumi

Koichi Satoh

Tsukasa Itoh

Hiroshi Watanabe

Nobuhiro Furukawa

Koichi Nishimura

Naoki Hiro

Takahiro Yamashita

Takahiro Isono

Yasushi Kuroda

Toshihiko Saitoh

Fusago Mizutaki

Takehiro Yonesaki

Masakazu Moroto

Yoshikazu Izumi

The battery charging detects battery temperature and includes a temperature maintaining charging operation wherein average charging current is controlled to drive battery temperature to a holding temperature, and charging is performed while maintaining battery temperature at that holding temperature. In addition, a temperature increasing charging operation occurs prior to the temperature maintaining charging operation. The battery is charged with a current which raises battery temperature until the holding temperature is reached. When battery temperature rises to the holding temperature in the temperature increasing charging operation, charging can transition to the temperature maintaining charging operation.

Battery charging method

The plateau region of P-C-T isotherm of a hydrogen absorbing alloy between the .alpha. phase region and .beta. phase region thereof is expressed by a normal cumulative distribution function wherein hydrogen content X is taken as frequency and the logarithm of equilibrium hydrogen pressure as a random variable. Parameters such as standard deviation .sigma. of the function are determined by numerical analysis based on measured data as to the equilibrium hydrogen pressure and hydrogen content of the plateau region of the alloy to be evaluated. Whether the equilibrium characteristics of the alloy are acceptable is determined using the parameters as evaluation criteria.

Method of discriminating equilibrium characteristics of hydrogen

Three types of novel hydrogen-absorbing alloy electrodes A, B and C usable for metal hydride secondary batteries are provided. All three types are represented by the general formula AB.sub.x wherein A represents Ti or elements that principally comprise Ti and generate heat upon absorption of hydrogen, B represents Mo and Ni or elements that principally comprise Mo and Ni and absorb heat upon absorption of hydrogen and 0.5.ltoreq.X.ltoreq.2, and are readily producible and difficult to undergo cycle deterioration and need only short activation treatment time. (A) uses a hydrogen-absorbing alloy obtained by quenching and solidifying an alloy melt under an atmosphere of a reducing gas containing hydrogen at a cooling rate of at least 1.times.10.sup.3 .degree. C./sec and having on the surface thereof a hydride layer; (B) uses a hydrogen-absorbing alloy having a composite phase structure comprising a main phase and a subphase, the average areal ratio of said subphase to said main phase in any cross-section of said alloy being 5 to 20%; and (C) uses a hydrogen-absorbing alloy having a composite structure comprising a main phase and subphase, said main phase comprising crystallites having a major axis length (a) of 0.8 to 6 .mu.m and a ratio of the major axis length (a) to minor axis ratio (b), a/b, of not more than 3.

Hydrogen-absorbing alloy electrode

A fuel cell system for directly converting chemical energy of a fuel into electric energy electrochemically. A fuel cell has a cathode and an anode. A main hydrogen absorbing alloy supplies hydrogen gas to the anode of the fuel cell during steady-state operation of the system. An auxiliary hydrogen absorbing alloy originally having a higher hydrogen gas absorbing/desorbing equilibrium pressure than the main hydrogen absorbing alloy at an equal temperature supplies hydrogen gas to the anode until the equilibrium pressure of the main hydrogen absorbing alloy, which is supplied an exhaust gas from the fuel cell is equal to a hydrogen gas absorbing/desorbing equilibrium pressure of the auxiliary hydrogen absorbing alloy, the auxiliary hydrogen absorbing alloy receiving the hydrogen gas from the main hydrogen absorbing alloy during steady-state operation.

Fuel cell system

A hydrogen absorbing alloy having a crystal structure of CaCu.sub.5 -type hexagonal system and represented by the general formula Re.sub.1-x Y.sub.x (Ni.sub.5-y G.sub.y).sub.z wherein Re is one of La, Ce, Nd, Pr, misch metal and lanthanum-rich misch metal, Y is yttrium, Ni is nickel, and G is an element capable of forming an intermetallic compound or complete solid solution in corporation with Ni or a mixture of such elements, and x, y and z are in the ranges of 0&lt;x.ltoreq.0.6, 0&lt;y.ltoreq.1 and 0.8&lt;z.ltoreq.1.2, respectively. This alloy has a high equilibrium hydrogen desorbing pressure at room temperature, a great capacity to absorb hydrogen and high durability to repeatedly absorb and desorb hydrogen.

Hydrogen absorbing alloy

Disclosed is a hydrogen-absorbing alloy electrode including a hydrogen-absorbing alloy capable of absorbing and desorbing hydrogen reversibly, the electrode being characterized in that the hydrogen-absorbing alloy forms a multi-phase structure composed of at least these three phases, a main alloy phase, an alloy phase of Ti.sub.2 Ni system cubic-structure and an alloy phase of Ti-Ni system monoclinic-structure, and the main alloy phase has TiMo-based crystalline cubic-structure.

A fuel cell system for directly converting chemical energy of a fuel into electric energy electrochemically. A fuel cell has a cathode and an anode. A main hydrogen absorbing alloy supplies a hydrogen gas to the anode of the fuel cell during steady-state operation of the system. An auxiliary hydrogen absorbing alloy originally having a higher hydrogen gas absorbing/desorbing equilibrium pressure than the main hydrogen absorbing alloy at an equal temperature supplies a hydrogen gas to the anode until the equilibrium pressure of the main hydrogen absorbing alloy, which is supplied an exhaust gas from the fuel cell is equal to a hydrogen gas absorbing/desorbing equilibrium pressure of the auxiliary hydrogen absorbing alloy, the auxiliary hydrogen absorbing alloy receiving the hydrogen gas from the main hydrogen absorbing alloy during steady-state operation.

In order to make a thermal utilization system operable in a stable and efficient condition regardless the variation of the operating heat source used, the system is provided with three hydrogen absorbing alloys having different pressure-temperature characteristics, wherein absorption/desorption of hydrogen gas is performed in two steps, i.e. the hydrogen gas desorbed from a first alloy is absorbed by a second alloy at a predetermined pressure, and is absorbed by the third alloy at a higher pressure after it is desorbed from the second alloy in a case when the temperature of the operating heat source is low, while the hydrogen gas desorbed from the first alloy is directly transported from the first alloy to the third alloy to be absorbed there when the temperature of the operating heat source is high. Alternatively, two hydrogen absorbing alloys having different pressure-temperature characteristics are used in such a way that, when the temperature of the operating heat source is low, the hydrogen gas desorbed from the first alloy is pumped to the second alloy to be absorbed there, but the gas is directly transported from the first alloy to the second alloy to be absorbed there when the temperature of the operating heat source is high.

Thermal utilization system using hydrogen absorbing alloys

A refrigerating and/or heating device of the contact type utilizing the endothermic and exothermic reactions of a hydrogen absorbing alloy comprises a contact member (16) in the form of a closed container (18) having a contact surface (17) and packed with a hydrogen absorbing alloy (19), a handle member (21) in the form of a closed container (22) packed with another hydrogen absorbing alloy (23), and a gas pipe (25) interconnecting the two members and having a valve (26).

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Osaka, Japan

Akio Furukawa