Device and method of monitoring the starting capability of a vehicles starter battery

<u>BACKGROUND OF THE INVENTION</u>

1. Field of the Invention

0001The present invention relates to monitoring apparatus and more particularly to an apparatus for monitoring the electric power of a motor vehicle's battery and method thereof, so as to issue an alarm if the power is lower than a predetermined level prior to starting the engine.

2. Description of Related Art

0002It is known that a driver has to start the engine of an automobile prior to driving it. Also, for successfully starting the engine, there must be sufficient power in the battery. In practice, however, there is no way for the driver to know the power level of the battery prior to starting the engine. It is often the case that the driver knows the battery is low only when the start fails. Alternatively, the battery may be already damaged before a next start attempt is made even it is successful in this next start.

0003Moreover, many different factors, such as ambient temperature, charging conditions and time, and load discharge, can affect the useful life of a battery. Thus, it is complicated. A conventional battery (e.g., NP battery) has the following characteristic curves regarding discharge time versus discharge voltage, ambient temperature versus available power of battery, and storage time versus available power of battery as shown in <figref idref="f0016">FIGS. 12 to 14</figref> respectively. Thus, for ensuring a successful start of the automobile, it is desirable to monitor the available power of battery on a long time basis in order to overcome disadvantages that may be caused by the above factors.

0004<patcit id="pcit0001" dnum="DE3901680"><text>DE 39,01,680</text></patcit> discloses a method for monitoring the cold starting ability of the starter battery for an internal combustion engine, in which the time profile of the voltage drop which occurs on starting is observed and evaluated. The evaluation is carried out on the basis of maximum ratings for a characteristic curve obtained from empirical values, and on the basis of the battery temperature. <patcit id="pcit0002" dnum="US6268712B"><text>US 6,268,712</text></patcit> discloses a method for determining the starting ability of the starter battery in a motor vehicle, in which the current/voltage value pairs for each instant are used to calculate a resistance value and the quantity of charge drawn from the storage battery, and the rate of rise in the resistance values as a function of the quantity of charge drawn is used to derive a measure of the availability of the storage battery during the starting procedure.

<u>SUMMARY OF THE INVENTION</u>

0005It is an aim of the present invention to provide a method for monitoring electric power in a motor vehicle on a long time basis.

0006The present invention provides a method for monitoring the electric power in a motor vehicle, utilising apparatus comprising a monitor and alarm device directly parallel connected to both a battery to be measured and a starting motor of the motor vehicle wherein the starting motor is taken as a load for forming an outer loop sampling circuit, a method of monitoring the motor vehicle's electric power in the outer loop sampling circuit comprising the steps of: <ol id="ol0001" compact="compact"><li>(a) in an outer loop sampling: taking a starting motor as a load, and sampling a battery to be measured every 1/t second for obtaining a sampled voltage;</li><li>(b) in a data storage: obtaining a voltage curve by connecting a plurality of continuous voltage values each sampled in every 1/t second;</li><li>(c) in a calculation: calculating a minimum voltage and recording the same;</li><li>(d) in a comparison: comparing a recorded minimum voltage with a predetermined alarm value so that, if the minimum voltage is higher than the predetermined alarm value, meaning that the battery is normal or meaning that the lowest point of the voltage curve has been reached or passed and the battery is determined to be abnormal; and</li><li>(e) in a result display: displaying a result of the calculation in the step (c) on a display, and issuing an alarm if the predetermined alarm value is reached in step (d);</li><li>(f) as a beginning: setting an interrupt vector address as a beginning of the process;</li><li>(g) as an initialisation: initialising registers and input/output (I/O) pins and enabling the interrupt vector and a timer, setting an initial value of a register, enabling the interrupt vector and the timer, and defining a status and an initial value of each pin respectively;</li><li>(h) setting a predetermined alarm value V_alarm and a time parameter t;</li><li>(i) setting an initial value of an ith sampling as zero and measuring an open-circuit voltage Vo;</li><li>(j) performing an increment of a number of a samplings i;</li><li>(k) sampling the battery every 1/t second for obtaining the ith sampled voltage;</li><li>(l) obtaining a voltage curve by connecting a plurality of continuous sampled voltage values Vi</li><li>(m) performing a calculating operation to find a function of a minimum voltage V_min and then to compare the minimum voltage V_min with the current sampled voltage Vi for replacing the current minimum voltage V_min with Vi if Vi less than the current minimum voltage V_min;</li><li>(n) comparing the current minimum voltage V_min with a predetermined alarm value V_alarm wherein, if the minimum voltage V_min is equal to or lower than the alarm value V_alarm, meaning that the lowest point of the voltage curve has been reached or passed and the process goes to step (o) else the process loops back to the step (j) representing the battery is normal; and</li><li>(o) issuing an alarm by a display prior to looping back to the step (j).</li></ol> whereby steps (a) to (e) are repeatedly performed for monitoring the battery for a long time, thereby informing a driver of a power level of the battery prior to starting an engine by noticing whether an alarm has been issued.

0007Preferably, t has a value between 1 and 10000, and, more preferably, t is 1000.

0008Advantageously, the minimum voltage V_min is obtained at the lowest point of the voltage curve during engine starting.

0009Preferably, a voltage value is obtained at any point of the voltage curve during engine starting, so that a voltage value at any point of a curve section from the point P2 where the engine is starting to the point P5 where an alternator is charging is taken as a battery measurement point.

0010Advantageously, in the method, an inner loop sampling circuit is formed by utilising an internal load of the monitor and alarm device, and alternatively performs different monitoring modes by suitably dividing time into a plurality of time intervals; a method of monitoring the motor vehicle's electric power in the inner loop sampling circuit comprising the steps of: (f) in an inner loop sampling: setting an internal load of the monitor and alarm device as a load, discharging the battery to be measured every T2 second by quickly switching a power transistor for obtaining a sampled voltage, and repeating the discharging N times so as to obtain N sampled voltage values; <ul id="ul0001" list-style="none" compact="compact"><li>(g) in a calculation: calculating an average voltage and recording the same;</li><li>(h) in a comparison: comparing the average voltage obtained in step (g) with a predetermined alarm value, displaying the result of the comparison in step (e) on the display, and issuing an alarm if the predetermined alarm value is reached; and</li><li>(i) in a time interval of measurement: measuring an available power of the battery every T2 second and waiting a predetermined period of time for the next measurement;</li></ul> whereby monitoring the battery for a long time is accomplished by repeating steps (f) to (i).

0011Preferably, the above method further comprises a process comprising: <ul id="ul0002" list-style="none" compact="compact"><li>(j) as a beginning setting an interrupt vector address as the beginning of the process;</li><li>(k) as an initialisation initialising registers and input/output (I/O) pins and enabling the interrupt vector and a timer, setting an initial value of a register, enabling the interrupt vector and the timer, and defining the status and an initial value of each pin respectively;</li><li>(l) setting an outer loop predetermined alarm value V_alarm, an inner loop predetermined alarm value v, and a time parameters t, T2;</li><li>(m) setting an initial value of an ith sampling as zero, and measuring an open-circuit voltage Vo;</li><li>(n) as a counting of time interval counting the number of time intervals using a counter; and</li><li>(o) determining whether an added time interval in the inner loop sampling step has reached T2 whereby, if not, the process goes to a subroutine (A) prior to looping back to step (n) else goes to a subroutine (B) prior to looping back to step (n).</li></ul>

0012Preferably, in the above method, the subroutine (A) is an outer loop sampling program taking the starting motor (S1) as a load, the subroutine (A) comprising: <ul id="ul0003" list-style="none" compact="compact"><li>(a1) performing an increment of a numberof samplings i;</li><li>(b1) sampling the battery every 1/t second for obtaining the ith sampled voltage;</li><li>(c1) obtaining a voltage curve by connecting a plurality of continuous sampled voltage values Vi;</li><li>(d1) performing a calculating operation to find a function of a minimum voltage V_min, and then to compare the minimum voltage V_min with the current sampled voltage Vi for replacing the current minimum voltage V_min with Vi if Vi less than the current minimum voltage V_min:</li><li>(e1) comparing the current minimum voltage V_min with the predetermined alarm value V_alarm whereby if the minimum voltage V_min is equal to or lower than the alarm value V_alarm, meaning that the lowest point of the voltage curve has been reached or passed and the subroutine (A) goes to step 16 else the subroutine (A) loops back to the step (f1) representing the battery is normal; and</li><li>(f1) issuing an alarm by a display.</li></ul>

0013Preferably, in the above method, the subroutine (B) is an inner loop sampling program by utilising an internal load of the monitor and alarm device, the subroutine (B) comprising: <ul id="ul0004" list-style="none" compact="compact"><li>(g1) enabling a load, conducting a power transistor for increasing a load current;</li><li>(h1) sampling voltage in every time interval of T2, and deriving a current by dividing the voltage by the resistance of the load so that this is also a current sampling step;</li><li>(i1) disabling the load and cutting off the power transistor for cutting off the load current;</li><li>(j1) determining whether the number of samplings has reached an integer N whereby if not, the subroutine (B) loops back to (g1);</li><li>(k1) obtaining an average of the sampled voltage values by calculation so that this is an average current calculation step;</li><li>(l1) comparing an average voltage with the inner loop predetermined alarm value v; and</li><li>(m1) displaying the result of a comparison in step (l1) on a display, and issuing an alarm if the alarm value is reached in step (l1).</li></ul>

0014Preferably, T2 has a value less than 1000_µsec, and more preferably, T2 has a value of 50 _µsec. Preferably, N has a value between 2 and 4.

0015Advantageously, the minimum voltage V_min is obtained at the lowest point of the voltage curve during engine starting.

0016Preferably, a voltage value is obtained at any other point of the voltage curve during engine starting so that a voltage value at any point of a curve section from a point P2 where the engine is starting to a point P5 where an alternator is charging is taken as a battery measurement point.

0017The above and other aims, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.

<u>BRIEF DESCRIPTION OF THE DRAWINGS</u>

0018<ul id="ul0005" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a flow chart illustrating a process of monitoring a motor vehicle's electric power according to a first preferred embodiment of the invention;</li><li><figref idref="f0002">FIG. 2</figref> is a detailed flow chart illustrating the <figref idref="f0001">FIG. 1</figref> process;</li><li><figref idref="f0003">FIG. 3</figref> is a block diagram of a first preferred embodiment of apparatus of monitoring vehicle's electric power according to the invention;</li><li><figref idref="f0004">FIGS. 3A, 3B</figref>, <figref idref="f0005">3C and 3D</figref> are graphs illustrating experimental values such as voltage values measured by the apparatus of the invention;</li><li><figref idref="f0006">FIG. 4</figref> is a block diagram of a second configuration of the monitor and alarm device being parallel connected to a current source to be measured according to the invention;</li><li><figref idref="f0007">FIG. 5</figref> is a block diagram of a third configuration of the monitor and alarm device being parallel connected to the current source to be measured according to the invention;</li><li><figref idref="f0008">FIG. 6</figref> is a block diagram of a fourth configuration of the monitor and alarm device being parallel connected to the current source to be measured according to the invention;</li><li><figref idref="f0009">FIG. 7</figref> depicts a circuit diagram of the apparatus being parallel connected to a battery to be measured;</li><li><figref idref="f0010">FIG. 8</figref> is a flow chart illustrating a process of monitoring electric power of a motor vehicle's battery according to a second preferred embodiment of the invention;</li><li><figref idref="f0011">FIGS. 9</figref>, <figref idref="f0012">9A</figref>, and <figref idref="f0013">9B</figref> are detailed flow charts illustrating the <figref idref="f0010">FIG. 8</figref> process respectively;</li><li><figref idref="f0014">FIG. 10</figref> is a diagram of time interval according to the second preferred embodiment process of the invention;</li><li><figref idref="f0015">FIG. 11</figref> is a circuit diagram according to a second preferred embodiment of the apparatus of the invention;</li><li><figref idref="f0016">FIG. 12</figref> is graph illustrating discharge time versus discharge voltage according to a conventional NP battery;</li><li><figref idref="f0016">FIG. 13</figref> is graph illustrating ambient temperature versus available power of battery according to the conventional NP battery; and</li><li><figref idref="f0016">FIG. 14</figref> is graph illustrating storage time versus available power of battery according to the conventional NP battery.</li></ul>

<u>DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS</u>

0019Referring to <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009">FIGS. 1 to 7</figref>, there is shown a first preferred embodiment of an apparatus and method thereof in accordance with the invention. In the apparatus, a monitor and alarm device 20 is parallel connected to both a battery to be measured B2 and a starter unit (e.g., starting motor as described below) S1. In a single loop, the starting motor S1 is taken as a load for forming an outer loop sampling circuit. 1/t second is set as a sampling time interval during discharging. A voltage curve is formed by connecting a plurality of continuous voltage values each sampled in 1/t second. Also, a minimum voltage of the curve is compared with a predetermined alarm value set by the invention so as to determine a status of the battery, thereby issuing an alarm in time if the status of the battery is abnormal.

0020Referring to <figref idref="f0001">FIG. 1</figref>, there is shown a process for monitoring a motor vehicle's electric power in accordance with the invention. The monitoring process comprises the following steps:

0021In step 1 (i.e., outer loop sampling), a starting motor S1 is taken as a load. The invention samples the battery to be measured B2 every 1/t second for obtaining a sampled voltage.

0022In step 2 (i.e., data storage), a voltage curve is obtained by connecting a plurality of continuous voltage values each sampled in 1/t second.

0023In step 3 (i.e., calculation), the invention calculates a minimum voltage and records the same.

0024In step 4 (i.e., comparison), the invention compares the recorded minimum voltage with a predetermined alarm value set by the invention. If the minimum voltage is higher than the alarm value it means that the battery to be measured B2 is normal. To the contrary, if the minimum voltage is equal to or lower than the alarm value it means that the lowest point of the voltage curve has been reached or passed and the battery to be measured B2 is determined to be abnormal.

0025In step 5 (i.e., result display), a result of calculation in step 3 is displayed on a display. Further, an alarm is issued if the alarm value is reached in step 4.

0026The steps 1 to 5 can be repeatedly performed so as to monitor the battery to be measured B2 for a long time. As a result, the driver can know the power level of the battery prior to starting the engine by noticing whether an alarm has been issued.

0027Referring to <figref idref="f0002">FIG. 2</figref>, there is shown a detailed flow chart illustrating the <figref idref="f0001">FIG.1</figref> process according to the invention. The process 10 comprises the following steps:

0028Step 11 is a beginning in which an interrupt vector address is the beginning of the process. Step 12 is an initialization in which registers and input/output (I/O) pins are initialized and the interrupt vector and a timer are enabled. Next, an initial value of the register is set, the interrupt vector and the timer are enabled, and status and initial value of each pin is defined respectively. In step 13, a predetermined alarm value V_alarm and a time parameter t are set by the invention. In step 14, initial value of the ith sampling is set as zero (i.e., count equal to 0) by the invention. Further, an open-circuit voltage Vo is measured. In step 15, an increment of i is performed. In step 150, the invention samples the battery to be measured B2 every 1/t second for obtaining the ith sampled voltage Vi. In step 151, a voltage curve is obtained by connecting a plurality of continuous sampled voltage values Vi. In step 152, the invention performs a calculating operation to find a function of the minimum voltage V_min and then to compare the minimum voltage V_min with the current sampled voltage Vi for replacing the current minimum voltage V_min with Vi if Vi is less than the current minimum voltage V_min In step 153, the invention compares the current minimum voltage V_min with the predetermined alarm value V_alarm. If the minimum voltage V_min is equal to or lower than the alarm value V_alarm it means that the lowest point of the voltage curve has been reached or passed and the process then goes to step 16. Otherwise (i.e., the battery to be measured B2 is normal), the process loops back to step 15. In step 16, an alarm is issued by a display. The process then loops back to step 15.

0029<figref idref="f0003">FIG. 3</figref> is a block diagram of a first preferred embodiment of the monitor and alarm device 20 for monitoring a vehicle's electric power according to the invention. The monitor and alarm device 20 is installed in an automobile and comprises a stabilization circuit 21, a CPU (central processing unit) or MCU (microprocessor control unit) 22, a voltage sampling circuit 23, a current control circuit 24, and a display circuit 25. The monitor and alarm device 20 is parallel connected to a current source to be measured 30. Each component is described in detail below. The stabilization circuit 21 acts to provide a constant current to the CPU or MCU 22 and other components. The CPU or MCU 22 acts to control sampling of voltage, data storage, calculation, comparison, result display, etc. The voltage sampling circuit 23 is commanded by the CPU or MCU 22 to fetch voltage data from the current source to be measured 30 every 1/t second. The fetch voltage data is then sent to the CPU or MCU 22 for processing. The display circuit 25 is commanded by the CPU or MCU 22 to show the measurement result on a LCD (liquid crystal display) or any of other suitable displays.

0030The current source to be measured 30 comprises the battery to be measured B2 and the parallel starting motor S1. Thus, the monitor and alarm device 20 is parallel connected to both the battery to be measured B2 and the starting motor S1 in which the starting motor S1 is taken as a load for forming an outer loop sampling circuit. Also, 1/t second is defined as a time interval. A voltage curve is formed by connecting a plurality of continuous voltage values sampled in the time intervals. Moreover, a minimum voltage of the curve is compared with a predetermined alarm value set by the invention so as to determine a status of the battery to be measured B2, thereby issuing an alarm if necessary.

0031<figref idref="f0004">FIGS. 3A, 3B</figref>, <figref idref="f0005">3C and 3D</figref> are graphs illustrating experimental values (e.g., voltage values) with respect to three different batteries as measured by the apparatus of the invention. In <figref idref="f0004">FIG. 3A</figref>, a voltage curve of the first battery to be measured begins from point P1 to point P2 where the engine is starting. A voltage measured at the parallel terminals is dropped significantly temporarily during the engine starting period, thus forming a lowest point P3 of the voltage curve. Hence, a minimum voltage is obtained at point P3. The minimum voltage is 8.88 V as indicated by cursor 2 (see <figref idref="f0004">FIG. 3A</figref>). A subsequent section P4 represents that the engine has been started. It is possible of determining whether the starting motor is operating normally by observing the curve section P4. For example, three ripples should be formed at the section P4 after the engine has been started if the starting motor is a three-phase motor. If the number of ripples is less than three it means that the starting motor does not operate normally. Hence, it is possible of determining whether the battery to be measured B2 is operating normally by observing the curve section P4. A final point P5 represents a charging point of an alternator. <figref idref="f0004">FIG. 3B</figref> is shown an enlarged view of the lowest portion of the voltage curve shown in <figref idref="f0004">FIG. 3A</figref>. The minimum voltage is 8.88 V as indicated by cursor 2. It is possible of observing a detailed variation of the voltage curve at this portion. In <figref idref="f0005">FIG. 3C</figref>, showing the second battery to be measured, the minimum voltage is 5.12 V as indicated by cursor 2. This means that the battery is about to be replaced. In <figref idref="f0005">FIG. 3D</figref>, showing the third battery to be measured, the minimum voltage is 1.11 V as indicated by cursor 2. A plurality of substantially parallel bar-waves are formed rather than a continuous curve consisting of small variations as indicated by the curve section P4 in <figref idref="f0004">FIG. 3A</figref>. This means that the starting motor is not operating normally. That is, the starting motor cannot be started by the battery having the minimum voltage. This means that the battery is dead. In view of the above, it is possible of determining whether the battery to be measured is operating normally by observing variations of the voltage curves measured with respect to three batteries. This is a significant characteristic of the invention.

0032Referring to <figref idref="f0006">FIG. 4</figref>, there is shown a block diagram of a second configuration of the monitor and alarm device 20 according to the invention. In the embodiment, the monitor and alarm device 20 further comprises a battery B2 polarity reverse protection circuit 26 for preventing a damage to the current source to be measured 30 from occurring due to polarity reverse of battery and an audio alarm circuit 27 commanded by the CPU or MCU 22 to issue an audio alarm on an occurred irregularity (e.g., power low, aging, or damage) of the battery B2 based on a measurement result.

0033Referring to <figref idref="f0007">FIG. 5</figref>, there is shown a block diagram of a third configuration of the monitor and alarm device 20 according to the invention. In the embodiment, the monitor and alarm device 20 further comprises a power detection circuit 28 commanded by the CPU or MCU 22 to fetch voltage data from the current source to be measured 30 for sending to the CPU or MCU 22 to determine a status of the charging battery B2 and subsequently send the status to the CPU or MCU 22 for further processing, a digital display 281 commanded by the CPU or MCU 22 to display the measurement result in a digital form, and a digital signal interface converter 282 commanded by the CPU or MCU 22 to communicate with the external through an interface based on the measurement result.

0034In the invention, the CPU or MCU 22 is able to detect whether a charging irregularity is occurred at the battery B2 since the monitor and alarm device 20 is parallel connected to the battery B2. Voltage measured on the parallel side will increase to a predetermined value during charging. In other words, a charging irregularity can be easily found if the voltage value does not reach to the predetermined value. Hence, it is possible of detecting the charging irregularity of the battery B2 by the power detection circuit 28. Also, the CPU or MCU 22 will issue an alarm in response to the charging irregularity.

0035Referring to <figref idref="f0008">FIG. 6</figref>, there is shown a block diagram of a fourth configuration of the monitor and alarm device 20 according to the invention. In the embodiment, the monitor and alarm device 20 further comprises a battery temperature sensor 291 and a battery temperature detection circuit 29 for sending temperature data of the battery sensed by the battery temperature sensor 291 to the CPU or MCU 22 so as to calculate a correct available power of battery by referring to a characteristic curve of battery temperature without being adversely affected by environment factors. The correct available power of the battery is in turn used for modifying an alarm value. For information about the available power of battery versus ambient temperature, refer to the characteristic curves in <figref idref="f0016">FIGS. 13, 14</figref> above.

0036Referring to <figref idref="f0009">FIG. 7</figref>, it depicts a circuit diagram of the apparatus. As shown, B3 represents a battery to be measured, S1 represents a starting motor, and D4 represents a LED.

0037Referring to <figref idref="f0010 f0011 f0012 f0013 f0014 f0015">FIGS. 8 to 11</figref>, there is shown a second preferred embodiment of the invention. In brief, a method of the invention comprises implementing a double loop technique to monitor an available power of the current source to be measured 30 in a long time basis, taking the starting motor S1 as a load for forming an outer loop sampling circuit, forming an inner loop sampling circuit by utilizing an internal load of the monitor and alarm device 20, alternatively performing different monitoring modes by suitably dividing time into a plurality of time intervals, and optimizing the same. Referring to <figref idref="f0003 f0004 f0005 f0006 f0007 f0008">FIGS. 3 to 6</figref> again, in the second embodiment the monitor and alarm device 20 further comprises a current control circuit 24 which is commanded by the CPU or MCU 22 to control and adjust current on a load so as to measure an output power of the current source to be measured 30.

0038<figref idref="f0010">FIG. 8</figref> is a flow chart illustrating a process of monitoring a motor vehicle's electric power according to the second preferred embodiment of the invention. It is found that the monitoring process on the outer loop sampling circuit is substantially the same as the first preferred embodiment. Thus a detailed description thereof is omitted herein for the sake of brevity. The monitoring process on the inner loop sampling circuit comprises the following steps:

0039In step 6 (i.e., inner loop sampling), an internal load of the monitor and alarm device 20 is set as a load. The invention discharges the battery B2 every T2 second (which is a very short period of time) by switching a power transistor for obtaining a sampled voltage. The discharging is repeated N times by the invention so as to obtain N sampled voltage values.

0040In step 7 (i.e., calculation), the invention calculates an average voltage and records the same.

0041In step 8 (i.e., comparison), as referring to the characteristic curves in <figref idref="f0016">FIGS. 12 to 14</figref> above, the gradient at the end of the characteristic curve tends to vary significantly, i.e., a correct prediction is difficult. Hence, the invention sets a predetermined alarm value in advance. The invention compares the recorded average voltage obtained in step 7 with the predetermined alarm value. Further, the result is displayed as in step 5. Furthermore, if the average voltage is equal to or lower than the alarm value an alarm is issued accordingly.

0042In a final step 9 (i.e., time interval of measurement), the invention measures the available power of battery every T2 second and waits a predetermined period of time for a next measurement.

0043By repeating steps in <figref idref="f0010">FIG. 8</figref>, it is possible of monitoring the battery B2 for a long time.

0044Referring to <figref idref="f0011">FIGS. 9</figref>, <figref idref="f0012">9A</figref>, and <figref idref="f0013">9B</figref>, there are shown detailed flow charts illustrating the process in <figref idref="f0010">Fig. 8</figref>. A process 10' according to the second preferred embodiment of the invention comprises the following steps:

0045Step 11 is a beginning in which an interrupt vector address is the beginning of the process. Step 12 is an initialization in which registers and I/O pins are initialized and the interrupt vector and a timer are enabled. Next, an initial value of the register is set, the interrupt vector and the timer are enabled, and status and initial value of each pin is defined respectively. In step 13, an outer loop predetermined alarm value V_alarm, an inner loop predetermined alarm value v, and time parameters t, T2 are set by the invention respectively. In step 14, initial value of the ith sampling is set as zero (i.e., count equal to 0) by the invention. Further, an open-circuit voltage Vo is measured. In step 18 (i.e., time interval counting), a counter of the invention begins to count the number of time intervals. In step 19 it is determined whether the added time intervals in the inner loop sampling step has reached T2. If not, the process 10' goes to subroutine (A) prior to looping back to step 18. If yes, the process 10' goes to subroutine (B) prior to looping back to step 18. The subroutine (A) is an outer loop sampling program by taking the starting motor S1 as a load. The subroutine (A) comprises the following steps: In step 15, an increment of i is performed. In step 150, the invention samples the battery to be measured B2 every 1/t second for obtaining the ith sampled voltage Vi. In step 151, a voltage curve is obtained by connecting a plurality of continuous sampled voltage values Vi. In step 152, the invention performs a calculating operation to find a function of the minimum voltage V_min and then to compare the minimum voltage V_min with the current sampled voltage Vi for replacing the current minimum voltage V_min with Vi if Vi is less than the current minimum voltage V_min In step 153, the invention compares the current minimum voltage V_min with the predetermined alarm value V_alarm. If the minimum voltage V_min is equal to or lower than the alarm value V_alarm it means that the lowest point of the voltage curve has been reached or passed prior to going to step 16 else it means that the battery to be measured B2 is normal. In step 16, an alarm is issued by a display.

0046The subroutine (B) is an inner loop sampling program by utilizing the internal load of the monitor and alarm device 20 as a load. The subroutine (B) comprises the following steps: In step 17, load is enabled. The power transistor is conducted for increasing the load current. In step 170, sample voltage in every time interval of T2. Also, a current can be derived by dividing the voltage to resistance of the load by the invention. That is, this is also a current sampling step. In step 171, the load is disabled. The power transistor is cut off for cutting off the load current. In step 172, it is determined whether the number of sampling has reached N, where N is an integer set by the invention. If no, the process loops back to step 17. If yes, the process goes to step 173. In step 173, an average of sampled voltage values is obtained by calculation. Also, this is an average current calculation step by referring to the well known current and voltage equation (i.e., V=IR). In step 174, the invention compares the obtained average voltage with the inner loop predetermined alarm value v. In step 175 (i.e., result display), a result of comparison in step 174 is displayed on the display. Further, an alarm is issued if the alarm value is reached in step 174.

0047Referring to <figref idref="f0014">FIG. 10</figref>, there is shown a diagram of time interval according to the second preferred embodiment process of the invention. Each of the subroutines (A) and (B) alternatively performs different monitoring modes by suitably dividing time into a plurality of time intervals so as to optimize the same.

0048Referring to <figref idref="f0015">FIG. 11</figref>, there is shown a circuit diagram according to the second preferred embodiment of the apparatus of the invention. As shown, a power transistor is labeled as Q1, a resistor as a load is labeled as R2, a battery to be measured is labeled as B3, a starting motor is labeled as S1, and a LED is labeled as D4. The resistor R2 may be eliminated if desired.

0049Note that t has a value between 1 and 10000. Preferably, t is 1000. T has a value lower than 1000 µsec. Preferably, T has a value of 50 µ sec. Preferably, N has a value between 2 and 4.

0050Further note that V_min is obtained at the lowest point of the voltage curve during engine starting in the above embodiments. In fact, V_min can be obtained at any of other points of the voltage curve during engine starting as shown in <figref idref="f0004">FIG. 3A</figref>. As shown, voltage at any point of a curve section from the point P2 (i.e.. the engine is starting) to the point P5 (i.e., charging point of the alternator) can be taken as a battery measurement.