Battery charge indicator
First Claim
1. A battery charge monitoring means for deriving an indication of the state of charge of a defined type of battery, the monitoring means having:
- means for sensing a load voltage proportional to current flowing when a defined type of battery is connected to a load, a fixed reference voltage which is less than the maximum voltage of the defined type of battery to which the monitoring means is to be connected, current sensing means capable of providing a voltage output proportional to the voltage drop within the defined type of battery when under load as a result of the internal resistance of the defined type of battery, means for sensing a dynamic reference voltage comprising the fixed reference voltage minus the voltage output of the current sensing means, comparison means capable of comparing (a) the load voltage and (b) the dynamic reference voltage, to provide an output indicative of the state of charge of the battery.
2 Assignments
0 Petitions
Accused Products
Abstract
An automotive battery charge indicator uses an algorithm expressed by fixed component values to determine if the remaining charge in the battery has fallen below a predetermined threshold. A current sensing resistor (8) (may be a Hall effect sensor or a discrete component having a resistance of the same order of magnitude as the internal resistance of the monitored battery (1)) is connected in series with the positive terminal (2) of a lead acid battery (1), and the positive side of a non-critical load (4). A percentage of the voltage across the load detected as input (6) is compared by comparator (11) with a dynamic reference voltage at input (5). The dynamic reference voltage is made up of a fixed reference voltage (7) less the voltage drop through current sensing resistor (8). When the percentage of load voltage at (6) is less than the dynamic reference voltage at input (5), the comparator provides a negative output at (12) indicating that the remaining charge in the battery has fallen below the preset threshold value. The output from the comparator can be used to operate an indicator such as an LED, or it could be used to initiate circuit shutdown to protect the battery from being discharged excessively.
66 Citations
10 Claims
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1. A battery charge monitoring means for deriving an indication of the state of charge of a defined type of battery, the monitoring means having:
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means for sensing a load voltage proportional to current flowing when a defined type of battery is connected to a load, a fixed reference voltage which is less than the maximum voltage of the defined type of battery to which the monitoring means is to be connected, current sensing means capable of providing a voltage output proportional to the voltage drop within the defined type of battery when under load as a result of the internal resistance of the defined type of battery, means for sensing a dynamic reference voltage comprising the fixed reference voltage minus the voltage output of the current sensing means, comparison means capable of comparing (a) the load voltage and (b) the dynamic reference voltage, to provide an output indicative of the state of charge of the battery. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification