When the battery voltage is below a first predetermined value, high charging rate current is supplied to the battery when the battery voltage is above a second predetermined value, the battery is supplied with trickle charging current. « lessĪ hysteresis type battery charger includes a circuit for monitoring battery voltage and in response controlling a pass transistor to supply charging current to a battery. The contents of the chassis are positioned to form a passage proximate the battery in communication with an inlet and outlet in the chassis to receive air for cooling purposes from an external source. Various vehicle function circuitry may also be positioned within the chassis. The cooler regulator activates and deactivates the peltier cooler elements in accordance with preselected temperature conditions within the chassis sensed by the temperature sensor. A cooling device within the chassis includes a cooler regulator, a more » temperature sensor, and peltier effect cooler elements. A heater device is positioned within the chassis which includes heater elements and a thermal switch which activates the heater elements to maintain the battery above a certain predetermined temperature in accordance with preselected temperature conditions occurring within the chassis. The charger receives direct current from an external direct current power source and has means to automatically selectively charge the battery in accordance with a preselected charging program relating to temperature adjusted state of discharge of the battery. « lessĪ chassis contains a battery charger connected to a multi-cell battery. An analog control system is employed to accomplish active input current waveshaping as well as the necessary regulation. The power circuit topology developed is a three switch design utilizing a power FET on the center tap of the isolation transformer and the power Darlingtons on each of the two ends. The combination of voltage and current requirements dictated the use of high power NPN Darlington switching transistors. The switches selected for the battery charger are the single most important item in determining its efficiency.
The battery charger circuit is an isolated boost converter operating at an internal frequency of 20 kHz. The state-of-charge definition employed is the energy remaining more » in the battery when extracted at a 10 kW rate divided by the energy capacity of a fully charged new battery.
SOLID STATE BATTERY CHARGER SOFTWARE
The BC/SCI has two major subsystems: (1) the battery charger power electronics with its controls and (2) a microcomputer subsystem which is used to acquire battery terminal data and exercise the state-of-charge software programs. The power circuit is capable of operating at 2 kW peak and 1 kW average power.
SOLID STATE BATTERY CHARGER SERIES
The battery charger has a full-wave rectifier in series with a transformer isolated 20 kHz dc-dc converter with high frequency switches which are programmed to actively shape the input ac line current to be a mirror image of the ac line voltage. A voltage level detector for controlling a battery charger is disclosed which includes a power supply circuit adapted to be coupled to a battery during charging thereof, a first voltage regulator for providing a supply voltage for the detector, the first voltage regulator being coupled to receive power from the power supply circuit, a second voltage regulator for providing a stable source of reference voltage, the second voltage regulator being coupled to receive power from the detector supply voltage, a voltage comparator having one input thereof coupled to the stable reference voltage source, circuitry for coupling the battery to the more » other input of the voltage comparator, the circuit for coupling being adapted to coupled a proportion of the battery voltage which proportion equals the stable reference voltage when the battery voltage reaches a predetermined maximum level, and control circuitry responsive to the output of the voltage comparator for controlling the charging of the battery in response to the battery voltage reaching the maximum desired level.
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