Patent ID: 7208917

Claim:
A serial charger with the function of automatic change of charging speed for NiCd/NiH batteries connected in series to allow for a multi-speed charging process in accordance with the number of the detected batteries, comprising: a) a housing adapted to receive charging components, the housing having a charging groove with a charging series loop for charging a plurality of batteries, a plug extending from the housing for an electric connection to an alternating current (AC) source; b) an exchange power unit disposed within the housing for converting AC into DC used for charging a plurality of series-connected batteries in the charging groove, the exchange power unit being adapted to provide a reference voltage to a charging control device; c) a plurality of switches parallel-connected with corresponding charging loops of the batteries, a unilateral electronic element being interposed between each switch and the positive terminal of the corresponding battery; and d) a charging control device having a microcontroller with a time control unit and a battery quantity/voltage detection system; the time control unit being adapted to control separately the on/off state of each switch, the battery quantity/voltage detection system being adapted to detect separately the terminal voltage at a positive terminal of the batteries of the battery charging loops as well as to determine the number of the batteries to be charged, the microcontroller taking control of a voltage regulation unit and a current regulation unit, the current regulation unit being coupled to a current detection unit, whereby the charging current and voltage are determined by the number (N) of the detected batteries; meanwhile, the charging current varies automatically in inverse ratio to the battery quantity (N), and the current variation phases depend on the number (N) of the batteries to fulfill a multi-speed charging function, and the finished charging time is automatically adjustable according to the number (N) of the batteries.