Circuit for measuring the capacity of a battery
US4931737A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 25, 1989 |
| Grant date | Jun 5, 1990 |
| Priority date | — |
| Expiry date | Apr 25, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R31/3832
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The discharge capacity of a secondary battery, e.g. a Ni-Cd battery, has a maximum value at room temperature and gradually decreases both with an increase and decrease of ambient temperature. The battery discharge capacity also varies inversely with the number of battery charge/discharge cycles of the battery. A circuit for measuring the remaining discharge capacity of the secondary battery comprises a capacitor (23) whose temperature and age-variation characteristics are very similar to those of the discharge capacity of the secondary battery. The current flowing through the battery and motor (13) is detected by a series resistor (17). A voltage follower (20) responds to the detected voltage and drives a resistor (24), so that capacitor (23) is discharged at a rate determined by the resistor (24) current. The capacitor voltage is compared with a predetermined value by a hysteresis comparator (29) which controls the ON/OFF state of a transistor (21) in accordance with the comparison. The comparator output pulses, i.e., the capacitor charge/discharge cycles, are counted by a counter (31). Since the capacitance variation of the capacitor corresponds to the variation in battery discha…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.