Battery cell size detection method

Abstract

A battery charger that is configured to charge different size battery cells and automatically determine the size of the battery cell to be charged. The battery charger includes at least one charging circuit and a microprocessor. The charging circuit, in turn, includes a serially connected switching device and a current sensing resistor and a first and second pair of battery terminals that are configured to receive different size battery cells. The first pair of battery terminals is serially connected to a size detection resistor. The serial combination of the first pair of battery terminals and the size detection resistor is connected in parallel with a second pair of battery terminals. The parallel combination is connected in series with the charging circuit. At a nominal charging current, the voltage at the battery terminals will vary by the voltage drop across the size detection resistor. Accordingly, by measuring the voltage at the battery terminals, the system can determine which pair of battery terminals is connected to a battery cell. By configuring the first pair of battery terminals to receive a first battery cell size, for example, size AAA, and serially coupling the first pair of battery terminals to the size detection resistor, and configuring the second pair of battery terminals to receive a second size of battery cell, for example, size AA, the battery cell size can easily be detected electronically by measuring the voltage at the battery terminals.

Dependencies are inferred from the claim text.