Method and apparatus for varying the sample rate of a fast battery charger
First Claim
1. A method of charging a battery, said method comprising the steps of:
- periodically sampling a measured voltage value of the battery during a charging sequence that includes a first predetermined interval characterized by a relatively low rate of increase in battery voltage and a second predetermined interval characterized by a relatively high rate of increase in battery voltage;
storing a predetermined number of consecutive voltage samples;
calculating an average voltage value from the stored voltage samples in order to determine the status of the charging sequence; and
changing the effective period over which said average voltage value is calculated as the charging sequence proceeds from said first predetermined interval to said second predetermined interval in the charging sequence.
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Abstract
This invention discloses a method and apparatus for rapidly charging a battery by monitoring the voltage of the battery and changing the effective sampling rate of the battery voltage during the charging sequence. More particularly, a first disclosed embodiment of the battery charging system takes voltage readings of the battery as it is being charged at a predetermined rate and stores the voltage values in a first-in, first-out stack in the order in which they are taken. Therefore, a stack of consecutive data samples spaced in time is created. During an interval in the charging sequence where the rate of increase in battery voltage is relatively low, the charging system retrieves voltage values from the stack which are widely separated in time to calculate a slope of the charging profile to determine the status of the charging sequence. During a second interval of the charging sequence when the rate of increase in battery voltage is relatively high, the effective sampling rate is reduced by taking sample points from the stack which are closer together in time. In this manner, the effective sampling rate of the charging system is changed to improve the effective signal-to-noise ratio of the system during the first interval while maintaining an appropriately fast response time during the second interval. An alternative embodiment is disclosed which changes the rate at which the battery voltage is sampled from the first to the second interval in the charging sequence.
132 Citations
19 Claims
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1. A method of charging a battery, said method comprising the steps of:
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periodically sampling a measured voltage value of the battery during a charging sequence that includes a first predetermined interval characterized by a relatively low rate of increase in battery voltage and a second predetermined interval characterized by a relatively high rate of increase in battery voltage; storing a predetermined number of consecutive voltage samples; calculating an average voltage value from the stored voltage samples in order to determine the status of the charging sequence; and changing the effective period over which said average voltage value is calculated as the charging sequence proceeds from said first predetermined interval to said second predetermined interval in the charging sequence. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus for charging a battery by applying a charging current to the battery and monitoring the battery voltage during a charging sequence that includes a first predetermined interval characterized by a relatively low rate of increase in battery voltage and a second predetermined interval characterized by a relatively high rate of increase in battery voltage said apparatus comprising:
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sampling for periodically sampling measured voltage values of the battery; a memory for storing a predetermined number of consecutive voltage samples; and controller means connected to said sampling means and said memory for calculating an average voltage value from the stored voltage samples and determining from said average voltage value the status of the battery charging sequence; said controller means further changing the effective period over which said average voltage value is calculated as the charging sequence proceeds from said first predetermined interval to said second predetermined interval in the charging sequence. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A method of controlling the charging of a rechargeable battery by monitoring the battery voltage during the charging sequence, the resulting battery voltage versus time charging curve from the charging sequence being characterized by a first region where the rate of increase in the battery voltage is relatively low and a second region wherein the rate of increase in the battery voltage is relatively high, said method comprising the steps of:
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periodically sampling at a substantially constant rate of voltage of the battery during the charging sequence; storing a predetermined number of consecutively sampled battery voltage values; and determining the status of the charging sequence from said stored voltage samples using stored voltage samples which were sampled over a first time period during said first region and using stored voltage samples which were sampled over a second time period shorter than said first time period during said second region. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification