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Method of determining and displaying battery charge status
| Details |
Inventors: Bergk, Gunther; Cimbal, Jochen;
Assignee: Braun Aktiengesellschaft (Frankfurt am Main, DE)
Primary Examiner: Brown; Glenn W.
Assistant Examiner:
Attorney, Agent or Firm: Fish & Richardson P.C.
A method of determining and displaying the charge status of a storage battery of a battery-operated appliance, such as a razor. A time-based charge status is calculated, based at least in part on the cumulative operating time of the appliance since recharging. The battery terminal voltage is also monitored. The time-based charge status is displayed until the battery voltage indicates a low voltage condition, at which point a low-charge alert indicator is displayed only if the time-based charge status is below a predetermined level (i.e., if the cumulative operating time is above a predetermined level). Methods of detecting battery aging, and for accounting for periods of excessive current flow, are included. |
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DETAILED DESCRIPTION OF EMBODIMENTS Referring first to FIG.
1 of the drawings, a load 2 is concerned to a battery (accumulator) B by means of an On/Off switch S and an electronic switching device 21.
The battery B can be recharged by means of a charging circuits not shown.
The electronic switching device 21 is driven by a pulse-duration modulator 4 via a driver circuit 3.
A counter 5 records the time period during which the load L, which has an essentially constant power consumption, is connected to the battery B via the switch S, the count starting from a fully charged condition of the battery.
The rated capacity of the battery B being also known, a display 9 indicating the charge status of the battery is controlled by the counter 5 on a time basis.
After a predetermined connection time has elapsed which is determined on the basis of the known power consumption and the known rated capacity of the battery B, such that the battery then contains only a low residual charge, counter 5 will deliver an output signal.
At this point, a charge indicator on display 9 will indicate the charge status "zero.
" This signal will cause the electronic switching device 21 to be driven.
Driving may be accomplished by a pulse-duration modulator 4 which gradually reduces the pulse duty factor for the control voltage down to zero, thus also gradually reducing the current flowing through the load 2.
An oscillator 6 provides the clock pulses for the counter 5 and the pulse-duration modulator 4.
Referring to FIG.
2, load 2 is a direct current motor M of an electric shaving apparatus, for example.
The series arrangement comprising the motor M and the switching transistor 21 is applied to the battery B via the On/Off switch S when the device is set in operation.
A diode 22 connected in parallel with the motor M prevents inductive voltage peaks.
The base of the switching transistor 21 is driven by the output of the pulse-duration modulator 4 via a driver circuit 3 comprised of transistors 31, 36 and resistors 32, 33, 34, 35, 37, 38
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Electrical and Wave 
