Battery cell size detection method
View Patent ↗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.
1. A multiple cell battery charger comprising:
a regulator for receiving a predetermined input voltage and supplying a regulated supply of DC voltage at its output;
at least one charging circuit, each charging circuit configured to charge one or more battery cells, said charging circuit electrically coupled to said regulator comprising:
a first pair of terminals for coupling to a first battery cell defining a first pocket;
a second pair of terminals for coupling to a second battery cell defining a second pocket;
a size detection resistor serially coupled to said second pair of battery terminals, said first pocket and said serial combination of said size detection resistor and said second pair of battery terminals coupled together in parallel defining a parallel combination;
a switching device, which forms a part of said charging circuit, serially coupled to said parallel combination for selectively connecting and disconnecting said parallel combination to said charging circuit; and
a microprocessor operatively coupled to said first and second pairs of terminals for monitoring the voltage applied to said pairs of terminals and selectively controlling the switching device to determine which pockets are populated with battery cells and electronically determining their sizes.
2. The multiple cell battery charger as recited in claim 1 , wherein said charging circuit automatically charges said battery cells according charging characteristics for the cell size determined to be populating the pocket.
3. The multiple cell battery charger as recited in claim 1 , wherein said first pocket is configured to receive battery cells of a first predetermined size.
4. The multiple cell battery charger as recited in claim 1 , wherein said second pocket is configured to receive battery cells of a second predetermined size.
5. The multiple cell battery charger as recited in claim 4 , wherein one or both of said predetermined sizes are fixed.
6. The multiple cell battery charger as recited in claim 4 , wherein said first and second predetermined sizes are different.
7. The multiple cell battery charger as recited in claim 1 , wherein said charging circuit is configured to enable said microprocessor to sense the voltage across said size detection resistor and determine whether a battery cell is populating said second packet as a function of the voltage across said size detection resistor.
8. The multiple cell battery charger as recited in claim 7 , wherein said size detection resistor is sized so that a nominal charging current flows through said size detection resistor when a battery cell of said second predetermined size is disposed in said second pocket.
9. The multiple cell battery charger as recited in claim 3 , wherein said first predetermined size corresponds to AAA.
10. The multiple cell battery charger as recited in claim 3 , wherein said second predetermined size corresponds to AA.