Have you ever wondered “why” your battery stops working? All batteries fail at one point or another and more importantly all batteries fail – due to different reasons. Specifically, two identical batteries that come from the same manufacturing batch, with the same identical voltage, capacity, and chemistry fail (or stop working) at different times. Why? To understand why batteries fail I will walk through the steps of a battery mode and effects analysis to discover modes of battery failure and the effects of the battery failure.
A battery mode and effects analysis is a procedure for identifying and understanding potential failure modes in a battery system. A battery mode and effects analysis contains four main steps or phases:
- Battery Mode Pre-work
- Battery Failure Severity
- Battery Failure Occurrence
- Battery Failure Detection
Battery Mode Pre-work
The Battery Mode Pre-work is an essential preliminary component to a battery mode and effects analysis and often times the one component that gets the least attention. It is a way of “starting smart” in the identification of battery failures. As an example, battery failures are often caused by shared interfaces. If an engineer, focused on a single facet of the battery’s micro or macro system, glosses over the effectiveness and efficiency of interfacing components when designing, compiling and assembling a battery’s system, then the failure rate and severity could dramatically increase regardless of how “correct” the engineer’s portion of the system is working. A really good case study on shared interface failures is the battery interface with the device’s operating system. The inefficiency of the operating system’s software in a device can under or over utilize the maximum capacity and voltage of a battery and thus subsequently degrade the battery faster then normal. At the consumer level they would just say the battery is bad or “sucks” when in fact it is the device’s software that is the culprit of faster than normal battery degradation.
Thus careful attention to a battery’s mode pre-work is well advised. Battery mode pre-work includes a complete and detailed description of the battery’s system, the battery’s function, the battery’s intended uses, and the probable unintended uses.
Battery Failure Severity
Identifying battery failure severity includes an assessment and subsequent severity rating or score of all failed modes and their effects – both direct and indirect. To assess all potential malfunctioning modes in a battery system it is important to notate the battery’s designed performance specifications. Knowing upfront how the battery should perform under designed specifications proves to be extremely helpful when determining every potential botched mode.
Potential mode malfunctions could include degradation, warping, incompatibility, misuse or abuse, erroneous algorithms, excessive voltage, improper operating conditions, faulty or weak internal system hardware etc. In addition failing modes have a direct and indirect relationship with an effect. For example the causality of a failed mode could be an electrical short-circuiting, corrosion or deformation.
The causality thus is what needs to be rated with regard to severity. More to the point, each failed mode has a failing effect on the function of the battery system. The effect is user perceived. If the battery user experiences “x” failure effect then the severity of the effect can be rated from 1 to 10 (a severity rating of 10 is the most extreme and is typically reserved for injury to a user).
One note on severity ratings is that there could be a consequential effect of the failed battery on interfacing systems. In another words an improperly performing battery may or may not be wholly contained within its own system. Depending on the severity of the malfunction the effect may go well beyond the battery’s system. Conversely and just as important in identifying the cause of the failed battery is the direct and indirect effect of the interfacing system – whereas the interfacing system could be the root cause of a malfunctioning battery.
Battery Failure Mode Occurrence
The next phase of a mode and effects analysis is the occurrence pattern of the failed battery. Simply enough – the occurrence pattern assesses how frequent a failure occurs. Since batteries that fail are looked upon as weak design it is important to know the type, effect, and frequency of a failed battery. This way a design change can be made and money can be saved.
To measure a frequency of a failing mode you can review similar product failure occurrences, processes, or datasheet (if previous examples are available) can be used. Or if previous examples are not available then a trial and error process could be conducted. Why is this important – because if a failed battery is ever rated in the 8-10 zone then you can bet someone is losing life, limb, and or property somewhere. And obviously you would not want to many occurrences at that level of severity.
Battery Failure Detection
Battery failure detection is method of inspection that is used when examining failure modes within a battery system. The method of detecting a battery failure begins with a review of existing system controls that are designed to prevent failure modes. Next comes testing, analysis, and monitoring failures. The purpose of which is to understand why a particular mode is failing. When a failure mode occurs, a detection number that represents the likelihood of detecting a failure mode, is subsequently assigned, and after a series of detections the total number of detection numbers are collected and added together to give a total score of battery failure modes; the lower the detection number is the better the overall battery system design schema.
Remember that the purpose of a battery failure mode and effects analysis is to identify and understand potential failure modes in a battery system. The reason why this is so important is that customers, who provide cash-flow (the lifeblood of a company), must be satisfied. Satisfaction as it relates to batteries is the lowest possible cost while still maintaining the best possible battery product. Thus insuring the lowest possible detection number is critically important to insuring the maximum potential of a company involved in battery design, manufacturing and sales.
Battery Failure Mode and Effects Analysis Summary
We looked a battery failure mode and effects analysis and learned how helpful this procedure is for analyzing potential failure modes in a battery system. Discovering potential defects in a battery design or manufacturing process is extremely helpful in controlling business expenses and losses as well helping to make more efficient the overall battery development project. A battery failure mode and effects analysis is also closely associated with six sigma methodologies and is a proactive tool for reducing errors, reducing expenses, and increasing profits. Now you could probably find a failure mode and analysis software online or you can build a custom template (that would be my preference) to suit your individual needs. Regardless, simply integrating a battery failure mode and effects analysis into your battery design process, battery manufacturing process, and battery sales process is a valuable tool in helping providing the best possible product to customers.