With the worldwide move toward electrification, battery performance is being taken to its extreme. Whether it is a micro-cell in a wearable devices or a huge high-voltage pack in an electric car, the data used to test the battery is only as good as the data used to test it. To engineers and manufacturers, the choice of battery testing equipment is a life-or-death situation in which the margin for error is non-existent.
Accuracy, Precision and Stability are three basic measurements used to define the quality of the testing hardware used in the field of power electronics and electrochemical analysis. Although these two terms are used interchangeably in everyday speech, they represent different technical terms that are essential in maintaining the reliability of data and maximizing the cycles of battery life.
Defining the Core Metrics
In order to be able to develop a professional system of battery testing, we must initially define our main measurements in a technically rigorous manner.
Accuracy: The Approximation of Truth
The approximation of the measurement to the true value is accuracy. In battery testing, it is the closeness of a reported voltage or current of equipment to the actual physical condition of the battery. When you have a cell at exactly 3.700 V, and your tester shows exactly 3.700 V, then the system is very accurate.
Accuracy is normally given as a percentage of full scale (FS) or percentage of reading. In systems such as State of Charge (SoC) and State of Health (SoH) estimation, there can be no compromise on the high accuracy, since even a small voltage offset can cause major errors in the calculation of the energy density.
Accuracy makes sure that whatever you have is physical reality, and that you are not in an over-discharge situation or an over-charge situation, which interferes with safety.
Precision: The Strength of Consistency
Precision is associated with repeatability and consistency. The capacity of a measurement system to give identical results under identical circumstances is known as its ability. A system may be accurate but not precise; an example is a tester that reads 3.705 V each time a 3.700 V cell is connected to it is precise but inaccurate.
Precision is also very important in battery R&D, where one needs to determine minor degradation trends. An engineer cannot differentiate between true variation in the behavior of a battery and typical signal noise unless there is high precision.
Precision enables it to identify the small electrochemical shifts with time, and this is crucial in comparative aging experiments.
Stability: The Power to be Consistent
Stability is the capability of ensuring consistency of measurements over a long duration of time. Such a measure takes into consideration the drift that is experienced with the aging of components or the change of environmental conditions. Where accuracy and precision refer to the picture at a point in time, stability refers to the reliability of the system in terms of weeks, months, or years.
Since the battery cycle-life test is an endurance sport, the stability is necessary to make sure that the data that is obtained on Day 1 can be directly compared with the data that will be obtained on Day 500.
High stability not only removes the frequent re-calibration process but the long-term data trends do not occur due to equipment, but rather the battery causes the trends.
A Comparative Explanation: The Target Analogy
As a more graphic representation of these differences, we can consider an analogy of target shooting, which is a typical standard in metrology.
- High Accuracy, High Precision:Measures are all centred around the true value.
- Low Accuracy, High Precision:Measurements are close to each other (consistent), even though they are quite distant (systematic error).
- High Accuracy, Low Precision: The means of the measurements are close to the center, whereas the specific points are scattered about (random error).
- Stability:It would be expressed as the shooter would maintain the same cluster in one position on the target over the course of a full day of shooting, despite becoming tired or when there was a change in the wind.
The Significance of Stability in Long-term Testing
Stability is a very neglected but important measure in the context of power electronics. Testing of batteries cannot be a one-time test; they have thousands of hours of operation.
Short vs. Long-term Stability
Short-term stability tends to be the ability of the system to resist noise and immediate variations in temperature in a single test cycle. Stability over the long term also includes the inception of internal shunts, voltage dividers, and Analog-to-Digital Converters (ADCs).
The measurement is drifted in case a battery tester is not stable. To scientists looking into new solid-state chemistries, the capacity loss of 2 percent per 1,000 cycles needs to be explained by the battery itself. From the departure of the equipment by 1 percent in the identical span, the research has been invalidated.
R&D is all about stability; accuracy is a position; stability will give you the precise location of the battery at this moment, but stability will give you the exact direction that the battery is taking as it advances.
Application Scenario Analysis
The accuracy, precision, and stability requirements vary with the magnitude and the intention of the test.
Scenario A: Consumer Electronics (milliampere-scale)
In the case of small cells, utilized in wearables or smartphones, the most important issues are resolution and precision. At the milliampere scale, the apparatus should be in a position to detect minute steps in change to determine self-discharge rates.
Focus: Finding small energy leaks referring to high-end cell quality.
Scenario B: EVs and High-Voltage Battery
At very high voltages (1000 V and above), accuracy and synchronization are of importance. One percent error in a high-power system does not merely lead to poor data; it can cost megawatts of power or worse, cause a safety failure that causes thermal runaway.
Focus: Allow simultaneous measurement of hundreds of channels to verify that the Battery Management System (BMS) is balancing cells properly.
Scenario C: Production and Quality in Industry
In a production system, the repeatability (precision) of multiple channels is king. When Channel 1 and Channel 100 on a large-scale test rig have different readings of the same cells, the manufacturer will not be able to ensure consistency in quality.
Focus: Interchannel consistency and high availability.
Eliminating Technical Problems in Measurement Reliability
These metrics cannot be achieved without advanced engineering to fight against the enemies of good data, signal noise, and thermal drift.
Signal Noise and Resolution
All electronic systems create noise, and in most cases, the source of noise is the switching power supplies that are being used to charge and discharge the battery. In high-performance systems, the advanced filtering and high-resolution ADCs are also utilized to ensure that the actual signal of the battery is not hidden by the power ripple.
The suppression of noise is needed to resolve the fine-grained reactions in electrochemical reactions during the end-of-charge process.
Thermal Effect and Drift of Measures
The greatest foe to consistency is temperature. During high-current tests, the electric properties of internal components change as they become hot. The equipment will experience thermal drift without effective thermal management, i.e., the high-level cooling designs in industry models such as Sinexcel-RE. Low-temperature-coefficient component-based systems are constructed with the zero point held fixed so that it does not get lost in the severe industrial environment.
Data integrity is not possible without thermal stability because when the temperature of the equipment is not regulated, the data is not reliable.
Equipment Choice: More Than The Spec Sheet
Engineers must not just choose a battery test system based on a single accuracy percentage in a brochure. The system architecture provides true data reliability.
- Calibration Periods:A system that is very stable will have a longer time before its specifications are compromised. This saves on the downtime and manual labor costs that come up due to the frequency of manual calibrations.
- Environmental Compensation: Sophisticated testers usually have onboard sensors that monitor ambient temperature changes in real-time and adjust the temperature before it occurs.
- Data Synchronization:In a multi-channel arrangement, the communication bus speed is critical. The high-speed ADCs should be able to transmit data without lags so that voltage and current sets are perfectly synchronized in time.
- Redundancy:In high voltage testing, redundant sensing (a sanity check) is used to make sure that the failure of one component does not cause erroneous data or dangerous overcharging.
The topmost engineering strengths, including the ones that were exhibited by Sinexcel-RE, focus on these architectural strengths to offer a set-and-forget (stability) level that is essential in the battery laboratories today.
Investment in long-term data security is the choice of equipment with installed thermal compensation and high-speed data buses.
Conclusion
Data is the most important asset in the competitive world of production and research of batteries. Making accuracy, precision, and stability the priority is not only a matter of adhering to a protocol, but it is a matter of providing the safety and efficiency of the energy transition.
Knowing the technical specifics of these measures, which include the accuracy giving the truth, the consistency giving the precision, and the time test giving the stability, engineers are able to choose those tools needed to design better and safer batteries. Good hardware minimizes signal noise, controls thermal effects, and offers the synchronized measurements needed in complex modern testing.
Frequently Asked Questions (FAQ)
Battery Tester Accuracy vs. Precision: What is the difference?
Accuracy is the ability of a measurement to be near the actual voltage or current value. Precision implies the form of consistency of such measurements when they are repeated under identical conditions. You can have an accurate tester (gives the same answer each time), though inaccurate (the result is always 10mV out ).
What is the importance of stability in battery cycle life testing?
The cycle life tests may take months. Stability makes sure that there is no drift of equipment during that period. Lack of stability will fail to provide you with an awareness of whether the reduction in the measured capacity is caused by the battery degrading or the equipment that loses its calibration.
What is the temperature sensitivity of the battery measurements?
Resistance varies with the temperature of the internal components in the tester. This thermal drift may lead to the equipment displaying varying values when it is warming up. Quality systems contain thermal compensation and sophisticated cooling to counter this.
What is the measurement drift of power electronics?
Measurement drift refers to the gradual variation in the output of a system when the input to the system is held fixed. During battery testing, aging components typically cause it, or temperature changes in the environment, which is the most significant risk to long-term stability.
What are the needs of testing high-voltage battery packs?
Extreme precision is needed to ensure safety in high-voltage testing (typically 1000 V and higher) and to coordinate the measurement of all cells. This is to guarantee that the BMS is filling the pack properly, and it does not result in dangerous overcharging conditions.
What is the reason signal noise occurs in battery testers?
Noise in the signal is usually brought in through the switching power supplies that are used to charge and discharge. Unless well filtered, this noise may cause the data to be “jittered,” making it hard to observe the actual electrochemical behaviour of the battery.
