Demonstration circuit 783 is a complete Fast Battery Charger capable of charging 1, 2, 3 or 4 series connected NiMH or NiCd cells using the LTC4060 linear battery charger. This demo circuit determines when the battery is fully charged using the -ΔV method with peak voltage and a safety timer as a backup termination. The input voltage range is 4.5V to 10V for a single cell and 8.6V to 10V for four cells.
The power portion of the circuit consists of a PNP power transistor constant current source which can provide up to 2A of charge current under some conditions. Jumpers are provided for programming charge currents of 0.5A, 1A or 2A. Other charge currents can be programmed by adding an external resistor to the PROG terminal post. Charge current greater than 2A can also be programmed by paralleling an external current sense resistor (R5) with the internal LTC4060 sense resistor).
Included on the board are jumpers to select NTC thermistor functions, battery chemistry, number of series cells, safety timer length, recharge voltage and two LEDs to indicate charger status. A power path FET is also included that provides a low loss path between the battery and an external system load when the input power is removed.