TWO CONTACT BATTERY SCHEME THAT ALLOWS CAPACITY AND THERMISTOR IDENTIFICATION
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2002-Feb-15
This invention eliminates two of the four bat- tery contacts presently necessary on the battery to determine the battery's capacity and thermistor val- ues. The proposal uses the capability of the charg- er's pp to read an A/D voltage to calculate a corresponding resistance. In the existing scheme, two independent A/Ds are used to determine the capacity resistor (Rc) and the thermistor (Rt) value. Since the pull up resistor value is a known constant, the JJP can calculate the resistance presented to the A/D for either Rc or Rt. The invention eliminates both of the above A/Ds and corresponding battery contacts. This is accomplished through the use of 4 switches: Ql, Q2, 43, and Q4. Refer to Block Dia- gram Proposed. In normal charging operation, the charge current would be enabled, and the switches would be conhgured in the following manner (Ql-06 Q2-tristate, Q3-tristate, and Q4-On) such that B- would be grounded and B+ would pass the charger current to the battery for charging. The diode D2 in the battery isolates the Rt and Z from the charger current.