Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
1999-03-13
2001-04-24
Wong, Peter S. (Department: 2838)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
C320S136000
Reexamination Certificate
active
06222370
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to energy source monitors, and in particular to a direct current energy source monitor capable of use with a plurality of different DC energy sources, such as batteries, wherein the energy sources have different nominal voltages from one another.
BACKGROUND
Direct current (DC) energy sources, such as batteries, are used in many situations where constant alternating current (AC) power is not available. Examples include auxiliary power for vehicles such as semi trucks, automobiles, ambulances, motorcycles, recreational vehicles, boats, and standby generators. Examples further include primary power for forklifts, trolling motors, golf carts, pallet trucks, floor scrubbers, wheel chairs, electric vehicles, and scissor lifts. The primary DC energy source used in such applications is a lead acid battery, typically ranging in nominal voltage from 6 to 48 volts.
In many applications, it is desirable or even critical to monitor the charge level of the energy source so that the user has an indication when the energy source is getting low on voltage or is deviating from a desired voltage range, and needs to be recharged or replaced. The voltage level on the energy source is a measurable indicator of charge of the energy source, and can be monitored with a device commonly known as a “monitor” or a “battery monitor” where the source is a battery. Without a monitor, typically the only inherent indication that a user has that the energy source is in a charged state is whether or not it activates the equipment to which it is attached. Many prior art devices exist which measure the voltage level on a battery or other DC energy source and display the charge level through some means (e.g., bar graph, digit readout, mechanical meter) but these devices generally work only for a particular nominal energy source voltage. That is, a prior art 12 volt DC source monitor will not properly monitor, or even work on, a nominal 24 volt energy source. Further, prior art DC monitors often require supplemental power besides the source being monitored in order to operate. The ability for a prior art monitor to work for a plurality of nominal source voltages generally requires some user interaction, for example, turning a knob to select a voltage, reading a printed conversion table, etc. A normal prior art single-voltage DC energy source monitor is typically constructed of a circuit which essentially is a set of voltage level comparators, with the thresholds for the comparators tied to some reference voltage and the output tied to a display device such as a light emitting diode (LED). This solution is impractical for a multiple-voltage DC monitor because with each type of DC source a complete set of comparators and associated reference thresholds must be included which eventually lead to a large, expensive circuit.
In many applications, it is desirable to monitor the direct current (DC) energy source capacity, aging characteristics, or capability of instantaneous current supply, commonly known as the DC energy sources' “condition” or “state-of-health.” The conductance of a battery is a measurable indicator of the “state-of-health”, and can be tested and/or monitored with a device commonly known as a “battery monitor.”
It is thus desirable that a DC energy source voltage monitor be provided which has the capability to automatically determine nominal voltages of the batteries intended for monitoring by the device, and which is relatively simple to manufacture. In addition, it is desirable to be able to monitor the state of health or battery condition, which can be indicated by conductance of the DC source.
SUMMARY OF THE INVENTION
The invention includes a DC energy source monitor (which will be known simply as a “monitor” herein for the sake of simplicity), such as a battery monitor, which automatically detects the nominal voltage of the DC energy source to which it is attached. It is understood that when the expression “battery monitor” is used herein with reference to the invention, that it includes more broadly a monitor for monitoring any source of direct current energy, and should not be considered as limited to a battery unless expressly stated as being so limited. The invention further includes a monitor which is self-powered from the DC source being monitored. In a first embodiment of the invention, a multiple nominal voltage monitor comprises an analog-to-digital converter configured to measure voltage from a DC source being monitored by the voltage monitor and generate a digital output corresponding thereto. The embodiment further includes a programmable control device configured to receive the digital output from the analog-to-digital converter and to look up a nominal voltage corresponding to digital output, and further configured to calculate a relative charge of the DC source as compared to a full charge from the nominal DC source. The first embodiment of the invention can further include a display in communication with the programmable control device and configured to display the nominal DC source voltage and the relative charge of the DC source as compared to a fully charged nominal source.
A second embodiment of the invention comprises the components of the first embodiment, and further comprises a voltage controlled oscillator configured to receive the voltage of the DC source being monitored and generate a frequency output proportional to the received voltage. The programmable control device is configured use the frequency output to determine the received voltage from the DC source.
In yet a third embodiment of the invention, a multiple nominal voltage DC energy source voltage monitor comprises the components of the first and second embodiments, and further comprises a calibration circuit configured to periodically calibrate the voltage controlled oscillator. The calibration circuit is configured to generate known voltages which are supplied to the voltage controlled oscillator. The voltage controlled oscillator is governed by a transfer function, wherein its output is a function of the input. The coefficients of the transfer function are calculated by the programmable control device based on the known voltages applied to the voltage controlled oscillator and the output produced by the voltage controlled oscillator in response thereto.
The invention further comprises a DC energy source voltage monitor which is powered by a power supply which is powered by the DC source being monitored. The power supply comprises a series voltage regulator utilizing a voltage reference with a power pass transistor.
The invention can further include a multiple nominal voltage direct current energy source monitor for monitoring the state of health of the energy source, including conductance, age, capability of the source to provide current, and charge capacity of the source.
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patent: 3873911 (1975-03-01), Champlin
patent: 3909708 (1975-09-01), Champlin
patent: 4825170 (1989-04-01), Champlin
patent: 5451881 (1995-09-01), Finger
patent: 5550475 (1996-08-01), Shafer
patent: 5574355 (1996-11-01), McShane et al.
patent: 5876870 (1999-03-01), Kawabata
Schousek Brian Walter
Schousek Theresa Jean
Luk Lawrence
Reid John S.
Reidlaw, L.L.C.
Wong Peter S.
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