Automatic electric battery charging apparatus
First Claim
1. Automatic electric battery charging apparatus, comprising means arranged to provide a control signal which follows variations in battery voltage comparatively rapidly, and a delayed signal which follows variations in battery voltage comparatively slowly, and means arranged to monitor the control and delayed signals and to reduce the average charging current when the difference between the control and delayed signals, or a signal which follows this difference comparatively rapidly, falls below a predetermined value.
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Abstract
An automatic electric battery charger which detects when the battery is fully charged by monitoring the rate of rise of battery voltage; when the rate of rise falls below a predetermined value, the charge is terminated. The rate of rise of voltage is detected by comparing an unprocessed battery voltage signal with a signal which follows the battery voltage signal with an exponential lag having a time constant of about 45 minutes. With a low rate of rise of voltage, such as occurs when the battery approaches the fully charged state, the lagging signal will tend to catch up with the unprocessed signal, and when the difference falls below 11 mV per cell, the charged is terminated.
In the preferred embodiment, the signal processing is digitally implemented, using a microprocessor.
18 Citations
19 Claims
- 1. Automatic electric battery charging apparatus, comprising means arranged to provide a control signal which follows variations in battery voltage comparatively rapidly, and a delayed signal which follows variations in battery voltage comparatively slowly, and means arranged to monitor the control and delayed signals and to reduce the average charging current when the difference between the control and delayed signals, or a signal which follows this difference comparatively rapidly, falls below a predetermined value.
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11. Automatic electric battery charging apparatus comprising means for monitoring a control signal which follows variations in battery voltage, and for providing a rate of voltage rise signal which is equal to a weighted average of the rate of rise of the control signal during a preceding part of the charge, the weighting factor being greatest for the most recent rise of the control signal and progressively less for earlier rises, and means for reducing the average charging current when the rate of voltage rise signal, or a signal which follows the rate of voltage rise signal, falls below a predetermined value.
Specification