U.S. Philips Corporation

Robert H Munning Schmidt

Geert J Bosscha

In a device where a load (R.sub.L) is powered by a battery (6) if a first detection device (100) detects that the expired discharge time measured by measurement means (40, 70) is equal to a first reference value stored in a memory (22), a first time measurement apparatus (40, 80) measures the time during which the load is powered by the battery. When the load is switched off and is not connected to the AC supply voltage via a power-supply circuit (1), the battery is discharged by a discharger (9). Second time-measurement apparatus (50, 80) measure the time during which the discharger is operative until a second detection device (13) detects a battery voltage at which the battery may be regarded as fully discharged. After comparison of the sum of the time intervals measured by the first and the second time-measurement apparatus with a second reference value stored in a memory (21), a correction device corrects the reference value stored in a memory (22) in such the way that during a next discharge the sum of the time intervals measured by the first and the second time-measurement apparatus is in better agreement with the second reference value.

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Drachten, Netherlands

Robert H Munning Schmidt