NOVELTY - The rechargeable battery (200) has charge data switching circuit (224) that has first switching unit connected to first terminal via first resistor and first diode, and second switching unit connected to first terminal via second diode. The charge data switching circuit is operable to switch first terminal between electrical charging interface (206) and data transfer interface (216). The rechargeable battery also includes fuel gauge integrated circuit (IC) (222) which is data connected to first terminal, and connected between positive electrode and negative electrode of battery cell (220).    USE - Rechargeable battery for use in bi-contact battery-charger system. Uses include but not limited to automobile starters, portable consumer devices, tools, uninterruptible power supplies, hybrid vehicles, electric vehicles, load leveling, and renewable energy uses.    ADVANTAGE - Provides a system for recharging a battery using only the positive and negative terminals used to provide the electrical energy for charging the battery, yet still senses data and temperature characteristics while maintaining or improving electrostatic discharge immunity. Uses a microprocessor that reduces the amount of time between temperature monitor operations as the battery approaches full charge.    DETAILED DESCRIPTION - The first terminal is provided on an external case which is also provided with a second terminal. The battery cell has a positive electrode connected to the cathode of the first diode, and a negative electrode connected to the second terminal. The first junction of the first switching unit is connected to the cathode of the first diode via a first resistor, while the anode of the first diode is connected to the first terminal. The first junction of the second switching unit is connected to the cathode of the second diode, while the anode of the second diode is connected to the first terminal. INDEPENDENT CLAIMS are also included for the following:    (1) Battery charger; and    (2) Battery charging method.    DESCRIPTION OF DRAWING(S) - The drawing is a block diagram showing the system for charging a battery using two interface contacts.    Rechargeable battery (200)    Electrical charging interface (206)    Data transfer interface (216)    Battery cell (220)    Fuel gauge IC (222)    Charge data switching circuit (224)