Abstract: A battery charge is provided which automatically controls the charging process independent of individual battery construction or temperature. Control of the charging process is achieved by periodically interrupting the charging current, determining resistance-free voltage of the battery in fixed intervals after interruptions of current, and comparing the resistance-free voltage with a reference voltage. Reference voltage is automatically determined for each recharging subject by analyzing the change in resistance-free voltage with respect to time during an initial, constant current period to locate certain characteristic points indicative of the onset of overcharge. The charging current is reduced as necessary, so that the resistance-free voltage does not exceed the reference voltage and significant overcharge is avoided.

Abstract: A charger for rechargeable cells or batteries utilizes a mechanism whereby resistance-free voltage is continually monitored during periodic current-off intervals in the charging process and compared to an independent reference voltage to prevent overcharge. After a certain degree of charge has been obtained, the current is gradually reduced to a finishing charge. Several means are provided for terminating the finishing charge while avoiding overcharge. Another embodiment of a charger provides for measurement of the resistance-free voltage during the current-off period after sufficient time is allowed for the recombination of any oxygen which may have been produced during charging, thus taking into account inherent variations in cells of the same type.

Abstract: A monitoring circuit is provided to monitor batteries while they are being charged or discharged, where the batteries comprise a series of modules or cells that are connected in series. A terminal is placed between each adjacent pair of modules and at each end of the battery, so that voltage across each module may be measured at the pair of terminals that define the module. Several different determinations of module voltage may be made during charge and/or discharge of the battery including the resistance free voltage of the module, and the module voltage while current is flowing through the battery. Generally, some or all of the modules are tested periodically, where the interruption interval for internal resistance free voltage determination may be in the order of 2 to 3 ms, and the testing frequency for the battery may be in the order of 0.5 to 25 Hz.

Abstract: Circuits are provided whereby rechargeable batteries and cells are charged very fast by a controlled current, and substantially at a rate never exceeding the ability of the battery or cell to accept current--i.e., to convert electrical current to stored chemical energy. The resistance free terminal voltage of the battery or cell is detected during an interval when the charging current is interrupted, and compared against an independent reference voltage to control the charging current when a difference between the reference voltage and the sensed resistance free terminal voltage exists. The reference voltage may be altered at any instant in time, as a function of the ambient temperature, or the internal temperature or pressure of the battery, as a function of the charging current when it is within a predetermined range, or if a particular change in the value of the charging current occurs over a predetermined period of time.

Abstract: A charging station for electric vehicles which have rechargeable batteries is provided. The charging station comprises a power section controlled by a fast acting power controller, a power connector and associated power cables for connecting to the vehicle, an interface with signal cables to carry status and/or control signals between the vehicle and the power controller, and a lockout which precludes delivery of power to the vehicle except when the power connector is in place. High charging currents are delivered to the battery of the vehicle as a consequence of signals at any instant in time to the power controller, so as to be able to turn delivery of the charging current on and off in less than a few milliseconds. The resistance free voltage of the vehicle battery is measured during intervals when the charging current is off, and the operation of the power controller is a function of the battery resistance free voltage at any instant in time.