Battery-pack fault detecting device and method for detecting fault of battery-pack

A battery-pack fault detecting device and a method for detecting a fault of a battery pack are provided. The battery-pack fault detecting device includes: N diodes, in which each battery is connected with one of the N diodes in anti-parallel via a detecting line; N+1 switches; a switch control circuit for switching on or switching off each switch; a voltage collecting circuit connected with the switch control circuit for collecting a voltage of the battery; an analog-to-digital conversion circuit for performing an analog-digital conversion on the voltage of the battery to obtain a digital voltage; a detection control circuit connected with the switch control circuit and the analog-to-digital conversion circuit, for controlling the switch control circuit to switch on or off each switch and for comparing the digital voltage with a preset value to judge a fault of the battery pack.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/CN2013/089666, filed on Dec. 17, 2013, which claims priority to, and benefits of Chinese Patent Application Serial No. 201210559350.2, filed with the State Intellectual Property Office of P. R. C. on Dec. 21, 2012, the entire content of all of which is incorporated herein by reference.

TECHNICAL FIELD

Exemplary embodiments of the present disclosure relate generally to the field of battery technologies and, more particularly, relate to a battery-pack fault detecting device and a method for detecting a fault of a battery pack.

BACKGROUND

Batteries are widely used in all kinds of electronic products like notebooks, mobile phones, and electric vehicles. Because a single battery usually cannot supply enough power, a plurality of single batteries are connected in series and/or in parallel to increase battery power or output efficiency.

In practice, many electronic products use a battery pack formed by a plurality of batteries connected in series as a power supply. In such case, an internal connection of the whole battery pack should be reliable, in order to avoid impact on power supplying due to a fault of a single battery. Otherwise, charging and discharging of the battery pack may be seriously affected and security of the battery pack cannot be guaranteed. Especially for a battery pack formed by lithium batteries, it usually needs a battery management system to detect the internal connection of the whole battery pack before starting the battery pack. Conventionally, a voltage of each battery of the battery pack is measured by a detecting device, and then the voltage is compared with a preset value to judge whether the battery has a fault. However, measuring the voltage by the detecting device needs an electric wire (i.e., a detecting line) to connect the battery and the detecting device. Because a distance between the battery and the detecting device is usually comparatively long, a comparatively long electric wire is easier to break down. However, an electric wire inside of the detecting device is comparatively short and thus it is not easy to break down. When the detecting device is connected to the battery via the electric wire, if a fault (such as an open circuit) is detected between both ends of a single battery, it's hard to judge whether the fault is caused by the single battery or by the electric wire.

SUMMARY

Embodiments of the present disclosure seek to solve at least one of the problems existing in the related art to at least some extent.

According to a first aspect of the present disclosure, a battery-pack fault detecting device is provided for detecting a fault of a battery pack containing a plurality of batteries connected in series. The battery-pack fault detecting device comprises N diodes, wherein each battery is connected with one of the N diodes in anti-parallel via a detecting line, and two adjacent batteries share one detecting line; N+1 switches; a switch control circuit, for switching on or switching off each switch, wherein each switch is connected between one diode and the switch control circuit; a voltage collecting circuit, connected with the switch control circuit for collecting a voltage of the battery; an analog-to-digital conversion circuit, connected with the voltage collecting circuit for performing an analog-digital conversion on the voltage of the battery to obtain a digital voltage; a detection control circuit, connected with the switch control circuit and the analog-to-digital conversion circuit, for controlling the switch control circuit to switch on or switch off each switch and for comparing the digital voltage with a preset value to judge a fault of the battery pack.

In one embodiment, the battery-pack fault detecting device further comprises a filtering circuit connected between the voltage collecting circuit and the analog-to-digital conversion circuit.

In one embodiment, the battery pack fault detecting device further comprises an alarm circuit connected with the detection control circuit for alarming the fault of the battery pack.

In one embodiment, the battery pack fault detecting device further comprises an (N+1)th diode for absorbing a surge, wherein a cathode of the (N+1)th diode is connected with a negative electrode of a first battery, and an anode of the (N+1)th diode is grounded.

According to a second aspect of the present disclosure, a method for detecting a fault of a battery pack containing a plurality of batteries connected in series is provided. The method comprises steps of: step 1, detecting a voltage of each battery in a preset sequence, specifically: only switching on two switches at both ends of an Nth battery each time, collecting a voltage of the Nth battery, and performing an analog-digital conversion on the voltage of the Nth battery to obtain a digital voltage; step 2, judging whether the digital voltage reaches a preset value A, if yes, following step 3; if no, following step 5; step 3, only switching on two switches at both ends of the Nth and an (N−1)th batteries; collecting a voltage V′n of the Nth and the (N−1)th batteries; and performing the analog-to-digital conversion on the voltage V′n to obtain a digital voltage V″n; only switching on two switches at both ends of the Nth and the (N+1)th batteries, collecting a voltage V′n+1 of the Nth and the (N+1)th batteries, and performing the analog-to-digital conversion on the voltage V′n+1 to obtain a digital voltage V″n+1; step 4, judging whether an average value of V″n and V″n+1 reaches a preset value B, if yes, judging that the Nth battery has a fault; if no, judging that detecting lines at both ends of the Nth battery have a fault; step 5, judging whether voltages of all batteries have been collected, if yes, terminating the fault detecting; if no, returning to step 1.

In one embodiment, the step 1 further comprises: filtering the voltage of the Nth battery before performing the analog-to-digital conversion on the voltage of the Nth battery to obtain a digital voltage.

In one embodiment, the step 3 further comprises: filtering the voltage V′n of the Nth and the (N−1)th batteries before performing the analog-to-digital conversion on the voltage V′n to obtain a digital voltage V″n; and filtering the voltage V′n+1 of the Nth and the (N+1)th batteries before performing the analog-to-digital conversion on the voltage V′n+1 to obtain a digital voltage V″n+1.

In one embodiment, the step 4 further comprises alarming that the Nth battery has a fault or the detecting lines at both ends of the Nth battery have a fault.

In one embodiment, each battery is connected with a diode in anti-parallel via a detecting line, and two adjacent batteries share one detecting line.

In one embodiment, the preset value A is a forward voltage drop of the diode connected with the Nth battery in anti-parallel.

In one embodiment, the preset value B is a sum of a rated voltage of the Nth battery and a forward voltage drop of the diode connected with the Nth battery in anti-parallel.

In one embodiment, the preset value B ranges from 95% to 105% of a rated voltage of the Nth battery.

With the battery-pack fault detecting device and the method for detecting the fault of the battery pack according to embodiments of the present disclosure, each battery is connected with one diode in anti-parallel, each switch is switched on or switched off by the switch control circuit controlled by the detection control circuit to select one or two batteries for detecting, a voltage of the one or two batteries is collected by the voltage collecting circuit and then the voltage of the one or two batteries is converted into a digital value, and the digital value is compared with a preset value. In this way, it is judged quickly which branch has a fault and whether the fault is caused by the battery or by the detecting line. The method is not only accurate and reliable but also may be implemented automatically and quickly. Moreover, the battery pack may be controlled selectively by using the device and the method.

DETAILED DESCRIPTION

In the specification, unless specified or limited otherwise, relative terms such as “central”, “longitudinal”, “lateral”, “front”, “rear”, “right”, “left”, “inner”, “outer”, “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “top”, “bottom” as well as derivative thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and may or may not require that the present disclosure be constructed or operated in a particular orientation.

As shown inFIG. 1toFIG. 3, a battery-pack fault detecting device according to an embodiment of the present disclosure is mainly for detecting a battery pack comprising a plurality of identical batteries connected in series and quickly judging whether a single battery or a detecting line has a fault. The battery pack fault detecting device according to an embodiment of the present disclosure comprises: N diodes which constitute a diode group2, N+1 switches which constitute a switch group3, a switch control circuit4, an analog-to-digital conversion circuit6, a voltage collecting circuit5and a detecting control circuit7. Each battery is connected with one of the N diodes in anti-parallel via the detecting line, and two adjacent batteries share one detecting line. Therefore, the number of the diodes of the diode group2is the same as the number of batteries of the battery pack1, the number of the switches of the switch group3is greater than the number of the batteries of the battery pack1by 1. Each switch is connected between one diode and the switch control circuit, that is, one end of each diode is connected with the switch control circuit4via one switch of the switch group3. The switch control circuit4is for switching on or switching off each switch of the switch group3and is electrically connected with the voltage collecting circuit5, the analog-to-digital conversion circuit6and the detection control circuit7in sequence. The diode of the diode group2may prevent the detecting line from floating when the detecting line is disconnected, so that the voltage collecting circuit5is connected with one end of the adjacent battery via the diode. And when there is a peak pulse of a relatively high voltage applied on the detecting line, the diode may be reversely conducted to release a peak voltage. The detecting control circuit7controls the switch control circuit4to send a signal to switch one or two switches on or off. After the one or two switches are switched on by the switch control circuit4, one or two batteries are connected with the voltage collecting circuit5via the one or two switches and the switch control circuit4. In this way, the voltage collecting circuit5collects a voltage of the battery, the analog-to-digital conversion circuit performs an analog-digital conversion on the voltage of the battery to obtain a digital voltage and then sends the digital voltage to the detecting control circuit7. The detection control circuit7compares the digital voltage with a preset value to judge a fault of the battery pack.

FIG. 2is a schematic diagram of a battery-pack fault detecting device according to an embodiment of the present disclosure. As shown inFIG. 2, a battery pack comprises N+2 batteries connected in series, a diode group2comprises N+2 diodes, and a switch group3comprises N+3 switches denoted from K0to Kn+2. Each battery is connected with one diode in anti-parallel via a detecting line, two adjacent batteries share one detecting line, and each diode is connected with a switch control circuit4via one switch. Therefore, one or two switches are switched off by the switch control circuit4when receiving a signal from the detection control circuit7. For example, a switch Kn−1 and a switch Kn are switched on so that the Nth battery is connected with the voltage collecting circuit5via the switches and the switch control circuit4, and thus the voltage collecting circuit5collects a voltage of the Nth battery. The analog-to-digital conversion circuit performs an analog-digital conversion on the voltage of the Nth battery to obtain a digital voltage, and sends the digital voltage to the detection control circuit7to be compared with a preset value and thus judging a fault of the battery pack. In order to improve an accuracy of the collected voltage, preferably, a filtering circuit8is connected between the voltage collecting circuit5and the analog-to-digital conversion circuit6, so as to filter the voltage collected by the voltage collecting circuit5before performing the analog-to-digital conversion on the collected voltage. By comparing the digital voltage with the preset value by the detection control circuit7, it is judged whether a branch comprising one or two batteries has a fault and whether the fault occurs to the one or two batteries or to the detecting line. In order to inform a user of a detecting result promptly, an output end of the detection control circuit7is electrically connected with an alarm circuit9for alarming the fault distinguishingly. Preferably, the battery pack fault detecting device further comprises a diode connected between the first battery and the ground. A cathode of the diode is connected with a negative electrode of the first battery, and an anode of the diode is grounded so as to absorb a surge close-by the battery. Structures of the switch control circuit4, the analog-to-digital conversion circuit6, the filtering circuit8and the alarm circuit9are well known by those skilled in the art.

According to embodiments of the present disclosure, a method for detecting a fault of a battery pack1is provided. As shown inFIG. 1toFIG. 3, the method comprises following steps.

In step 1, a voltage of each battery is detected in a preset sequence, that is, only two switches at both ends of an Nth battery are switched on each time, a voltage of the Nth battery is collected, and an analog-digital conversion is performed on the voltage of the Nth battery to obtain a digital voltage. For example, the switch control circuit4switches on a switch Kn−1 and a switch Kn, thus collecting the voltage of the Nth battery.

In step 2, it is judged whether the digital voltage reaches a preset value A, if yes, step 3 is followed; if no, step 5 is followed. That is, by comparing the digital voltage Vn of the Nth battery with the preset value A, it is judged whether the digital voltage reaches the preset value A, if yes, it is indicated that a branch comprising the battery has a fault, step 3 is followed to detect two batteries, so as to further judge whether the battery or the detecting line has a fault; if no, step 5 is followed.

In step 3, only two switches at both ends of the Nth and an (N−1)th batteries are switched on, a voltage V′n of the Nth and the (N−1)th batteries is collected, and the analog-to-digital conversion is performed on the voltage V′n to obtain a digital voltage V″n; only two switches at both ends of the Nth and the (N+1)th batteries are switched on, a voltage V′n+1 of the Nth and the (N+1)th batteries is collected, and the analog-to-digital conversion is performed on the voltage V′n+1 to obtain a digital voltage V″n+1. In this step, a first double-battery group (i.e., the Nth and the (N−1)th batteries) and a second double-battery group (i.e., the Nth and the (N−1)th batteries) are detected respectively. The detection control circuit7sends a signal to only switch on the two switches Kn and Kn+2 at both ends of the Nth and the (N−1)th batteries to detect the voltage of the first double-battery group, and sends a signal to only switch on the two switches Kn−1 and Kn+1 at both ends of the Nth and the (N+1)th batteries to detect the voltage of the second double-battery group. It should be noted that a detecting sequence of the voltage V′n and V′n+1 may be exchanged.

In step 4, it is judged whether an average value of V″n and V″n+1 reaches a preset value B, if yes, it is judged that the Nth battery has a fault; if no, it is judged that detecting lines at both ends of the Nth battery have a fault.

In step 5, it is judged whether voltages of all batteries have been collected, if yes, a fault detecting is terminated; if no, step 1 is followed. A method for judging whether the voltages of all batteries are collected or not is well known by those skilled in the art, for example, it may be realized by judging whether all adjacent switches have been switched on simultaneously.

As shown inFIG. 1, if it is found that a branch comprising the Nth battery has a fault, no matter the Nth battery or the detecting line has a fault, the diode is connected with the voltage collecting circuit4via switches at both ends of the diode and the switch control circuit4, therefore the preset value A is a forward voltage drop of the diode connected with the Nth battery in anti-parallel. The forward voltage drop of a common diode is 0.7 V, but because the battery pack fault detecting device is usually influenced by an environmental electromagnetic interference, the preset value A preferably ranges from 90% to 110% of the forward voltage drop of the diode. For example, when the voltage Vn of a single battery approximates zero, it may be judged that the branch comprising the single battery has a fault. The batteries of the battery pack1are usually of a same type, so the diodes of the diode pack2are usually of a same type.

Further, the Nth battery is judged to have a fault when the average value of V″n and V″n+1 reaches the preset value B. The preset value B may be a sum of a rated voltage of the Nth battery and the forward voltage drop of the diode. A reason may be illustrated as follows. As shown inFIG. 1, given that the voltage of single batteries with the same type is U, the forward voltage drop of each diode is V, when the Nth battery has a fault, V′n=U+V, V′n+1=U+V, so the average value of V′n and V′n+1 is U+V. When a detecting line connected with a positive electrode of the Nth battery (i.e., the detecting line connected with a negative electrode of the (N+1)th battery) has a fault, V′n=U+V, V′n+1=2 U, so the average value of V′n and V′n+1 is 1.5 U+0.5V. A value of V is usually very small, and the battery-pack fault detecting device is usually influenced by the environmental electromagnetic interference, so the preset value B may range from 95% to 105% of the rated voltage of the Nth battery. Each battery is connected with one diode in anti-parallel via the detecting line, which may prevent the detecting line from floating when the detecting line is disconnected, so that the voltage collecting circuit5is connected with one end of the adjacent battery via the diode. And when there is a peak pulse of a relatively high voltage applied on the detecting line, the diode may be reversely conducted to release a peak voltage. Preferably, the step 10 further comprises filtering the voltage of the Nth battery before performing the analog-to-digital conversion on the voltage of the Nth battery, so as to reduce an influence of external interference on the detected voltage. Moreover, because a branch fault judged by the detection control circuit7may be a fault of the battery or a fault of the detecting line connected with both ends of the battery, preferably, the step 4 further comprises alarming that the Nth battery has the fault or the detecting lines at both ends of the Nth battery have the fault so as to allow the user to get the fault in details and on time.

With the battery-pack fault detecting device and the method for detecting the fault of the battery pack according to embodiments of the present disclosure, it is judged quickly which branch has a fault and whether the fault is caused by the battery or by the detecting line. The method is not only accurate and reliable but also may be implemented automatically and quickly. Moreover, the battery pack may be controlled selectively by using the device and the method.