This application note describes how Constant Current Regulators (CCRs) can be used in low-cost charging circuits for the three most common types of rechargeable batteries. The CCR provides a simple controller to terminate charging when Nickel Metal Hydride and Nickel Cadmium batteries reach the predetermined peak voltage of 1.5 V per cell. The CCR controller can also be used for recharging Lithium Ion batteries by eliminating trickle charges, which prolongs battery life by maintaining battery temperature in safe operating range.