Patent ID: 6707273
Filing Date: 2004-03-16
Classification: H02J

Abstract:
Apparatus for supplying a controlled charging current to a sealed rechargeable battery having at least one cell and of the type which during the process of being recharged creates self-generated heat and has both a critical temperature limit and a requirement for a certain amount of self-generated heat to reach a full capacity of recharge, comprising:(a) means adapted to be connected to an external AC electrical source for providing a DC charging current; (b) controllable switching means connected in series between said means for providing a DC charging current and said battery and operable between a conducting state wherein charging current is supplied through the switching means to the battery and a non-conducting state wherein the switching means blocks the flow of charging current to the battery; (c) thermal sensing means bonded to the battery and operative to develop a control voltage according to the temperature rise of the battery and the ambient temperature at the battery location, the combined temperature being referred to as the absolute temperature of the battery; (d) switching control means responsive to both the control voltage developed by the thermal sensing means and the voltage of said battery for developing a set voltage whose value depends on both said control voltage and the voltage of said battery and is operative when said set voltage is below some given value for maintaining said switching means in a conducting state during which said charging current is enabled to flow through the switching means at a relatively high rate and operative when said set voltage is at or above said given value for maintaining said switching means in a non-conducting state, said switching means being operative such that said given value corresponds to a value indicating that the battery has reached a preset percentage within the range of 80-95% of its full capacity; (e) a shunt resistor connected between the input and output terminals of the switching means for providing a relatively slow rate of charging current between said charging current providing means and the battery when said switching means is in a non-conducting state and to maintain said charging current at a level such that during passage of said charging current through said shunt, the back emf of said battery is kept high enough to keep said switching means in a non-conducting state, low enough to avoid deterioration of said battery and sufficient to cause said battery to reach substantially full charge; and (f) wherein the components of said apparatus are selected to vary said set voltage in accordance with a profile relating said set voltage to said battery absolute temperature.