Temic Telefunken Microelectronic Gmbh

Dieter Hanselmann

Karl-Diether Nutz

Bernd Mayer

Stepfan-Peter Weller

The invention relates to a charging method for storage batteries, in particular for NiCd and NiMH cells. According to the invention, the rise in the charging voltage during each of a number of consecutive charging cycles of a specified duration is measured in the form of a unit corresponding to a certain voltage. The number of these units is transmitted in the form of a counting pulse to two up-down counters during the period of the charging cycle, whereby one counter functions in the down mode and is set at the beginning of a charging cycle to a number corresponding to the number of units established in the preceding charging cycle. In the following charging cycle, the roles of the two counters are reversed, so that the up-counter is now set to the down mode and the other counter to the up mode, whereby the latter is set to a Certain starting counting status. At the end of each charging cycle, the final status of the down counter is compared with the specified starting status, from which a switch-off criterion is derived for the charging process. According to the invention, this process enables both positive and negative changes in the dU/dt value of the charging curve to be detected with a high voltage resolution and, at the same time, minimal cost.

Charging method for storage batteries

A charging method for storage batteries, in particular for NiCd and NiH cells. In accordance with the invention, the charging operation is cyclically interrupted for the purpose of measuring the charging voltage. During these measurement intervals, the charging voltage is cyclically compared with a reference value. If the value of the actual charging voltage is greater than this reference value, the latter is increased by a certain amount to match it to the actual value of the charging voltage and then stored. By contrast, the number of measurement cycles is counted in which the value of the measured charging voltage is consecutively equal to or less than the maximum stored reference value. Finally, the charging current source is switched off or the charging current is reduced at a preset counter reading. As a result, maximum utilization of the available effective capacity together with extensive protection against overcharging is achieved. In addition, the method in accordance with the invention ensures the inexpensive provision of a charging circuit.

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Ohringen, Germany

Dieter Hanselmann