Versatile Battery Chargers for New Age Batteries

This paper proposes two designs for a versatile charger capable of charging a range of batteries ranging from the conventional Li ion and Ni-Cd batteries to the more recent thin film batteries. The charger is equipped with a low power micro controller which enables the user to specify the kind of battery to be charged as well as calibrate the current and the voltage levels. The charger is capable of working in both, the Constant Current (CC) as well as the Constant Voltage (CV) mode. The constant current mode has the options of trickle charge and fast charge, the values of which can be calibrated beforehand. The charger implements a simple and efficient algorithm using the micro controller to decide the charging methodology and also detect end-points to avoid overcharging. One of the designs offers a very high accuracy of 0.02%/V in the charging current across input voltage values ranging from 2V to 5.5V, while the other has a power consumption of less than 1mW (for charging at 3V and current values of the order of a few microamperes), which opens up the possibility of powering the device using energy harvesting sources.