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# Available Battery Time Sensor

IP.com Disclosure Number: IPCOM000079963D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 35K

IBM

## Related People

Ferraiolo, FA: AUTHOR [+2]

## Abstract

In standby power systems using rechargeable batteries for a temporary source of power when the utility fails, one of the valuable pieces of information is the amount of time remaining that the battery can supply power before it is discharged. The circuit provides time remaining until the battery is discharged, taking into consideration the present load on the battery.

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Available Battery Time Sensor

In standby power systems using rechargeable batteries for a temporary source of power when the utility fails, one of the valuable pieces of information is the amount of time remaining that the battery can supply power before it is discharged. The circuit provides time remaining until the battery is discharged, taking into consideration the present load on the battery.

This circuit subtracts the minimum usable battery voltage from the actual measured battery voltage, to obtain the voltage remaining to be used. This voltage is fed through a differentiator circuit to obtain the rate of voltage decay. Both of these voltages are fed into an integrated circuit analog divider, which divides the voltage remaining by the rate of decay of the voltage to obtain the time remaining.

The circuits are feedback amplifier types for performing the functions, such as the subtraction and differentiation as shown in the figure. Potentiometer 1 and resistor R4 used in the subtraction circuit are adjusted so that the minimum battery voltage is set to 0.

Pot 1 is adjustable so that the magnitude can be varied. Resistors R1, R2 and R3 divide the voltage output by 2 so that an input change, for example, from 220 to 200 gives an output voltage from 10 volts to 0 volt. This is shown in the circuit as voltage Vz. This voltage is applied to the differentiator which produces an output proportional to the rate of voltage change (dv/dt). The inverter stage produces ...