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BATTERY CONTACT ELIMINATION THROUGH DUAL USE OF RT LINE FOR TEMPERATURE AND CAPACITY

IP.com Disclosure Number: IPCOM000007606D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2002-Apr-09
Document File: 2 page(s) / 102K

Publishing Venue

Motorola

Related People

Joseph Patitio: AUTHOR

Abstract

This invention provides a means of detecting the battery's temperature and capacity or related param- eter while eliminating a battery contact and associated charger contact by using the existing thermistor port in a dual function capability. This is a cost savings to the battery and charger.

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MO7VROLA Technical Developments

BATTERY CONTACT ELIMINATION THROUGH DUAL USE OF RT LINE FOR TEMPERATURE AND CAPIiCITY

by Joseph Patitio

  This invention provides a means of detecting the battery's temperature and capacity or related param- eter while eliminating a battery contact and associated charger contact by using the existing thermistor port in a dual function capability. This is a cost savings to the battery and charger.

  Refer to "Existing Block Diagram" attached. Existing batteries require two separate battery con- nections to determine the battery's temperature and battery capacity. This invention uses the capability of the charger's pp to read an A/D voltage, along with a unique switching algorithm to determine the battery's capacity and temperature with only one battery connection, thus eliminating the additional connection. The need for the Rc A/D input in the charger's microprocessor and its associated circuitry is no longer necessary

  Refer to "Proposed Block Diagram" attached. The invention uses the capability ofthe charger's pp to read an A/D voltage to calculate a corresponding resistance. To determine the Rt value the charger circuit merely disables the charge path such that no current is inputted into the battery. This causes the transistor Ql in the battery to be unbiased. In this state the charger can read the voltage at the A/D input (Vx) and read only the Rt resistor. The equa- tion for the Rt resistor is as follows:

Requivalent (with Rc switched out) = Rt = (Vx) (Rl)

5.vx

  Once the Rt is determined, the charger can now turn on a precharge current to begin to prepare the battery for charging. The transistor Ql is now biased

via resistor R2 (large enough resistance value to assure charging current will not damage resistor R2 or transistor Ql and that heat dissipation will not be an issue). The Rc resistor is now switched in paral- lel with the previously determined Rt resistor. The A/D voltage yields the result of the voltage division of Rt and Rc in parallel with the pull up resistor Rl pulled up to 5V The collector to e...