Arbin News Archives - Page 3 of 4

Category: Arbin News News

Evaluating Battery Test Equipment 5: Accuracy

October 18, 2018

Accuracy represents the trueness of test equipment measurement; the closeness of average sample to its true value. Specifying this metric requires comparison to a known source such as a high-performance meter.

Plot of -200A discharge pulse on two different testers.

Accuracy should not be confused with noise. The relationship between “accuracy” and “precision” relates to the measurement noise. As stated above, accuracy is how close the average measurement is to the true value largely ignoring noise. Precision specifies to the amount of noise that will be present. Therefore, an instrument with good accuracy can still have a noisy measurement if it has poor precision and can be affected by temperature fluctuations.

Translating this into test results...
Note the plot and description above. Many types of battery test equipment will have similar accuracy specifications, and while this is important, it should be evaluated in combination with the instrument’s resolution and precision. The accuracy metric alone can hide the true performance difference of the equipment.

Calibration is another related factor to question during evaluation. Battery test equipment that is sufficient to use a simple hand-held meter during calibration will not produce results any better than the meter. Arbin calibration requires a 6.5 digit or better digital multi-meter and some equipment will require 8.5 digit or better. NIST-traceability is maintained for meters used in all factory calibrations.

Inadequate meter for calibration

6.5 digit (or better) meter should be used for calibration.

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Evaluating Battery Test Equipment 4: Robustness

October 18, 2018

Robustness - the quality of materials and quality of construction have a major impact on how long the test equipment lasts and how long it will hold calibration.

Resistance to corrosion and temperature fluctuations are significant attributes of high-quality test equipment. The instruments duty cycle and the maximum power rating also heavily contribute the usefulness and longevity of the equipment.
Long-term battery testing requires test equipment to run continuously. Modern batteries are designed to run for thousands of cycles at a minimum, while xEV and grid storage applications require batteries to last 10’s or even 100’s of thousands of cycles. High-quality test equipment that can operate without interruption is necessary for such applications. Likewise, the power demands for modern batteries make it important to verify the max power rating of test equipment. Many will not be rated to operate at a maximum calculated power (max voltage x max current), especially with a 100% duty cycle.

Low quality equipment is known to have a high failure rate and may not hold calibration. Frequent calibration checks and re-calibration will be required, which affects the validity of results data. Replacing failed test equipment on a regular basis also affects the validity of test results across this period.

Arbin 96-channel cycler using bipolar circuitry and designed for continuous operation.

Translating this into test results...
Arbin testers have corrosion resistant coatings on all circuitry. The high-quality materials offer better natural resistance to temperature fluctuations and some products have special thermal management technology inside for sensitive components (ask your Arbin sales rep for more information). Arbin test equipment is also engineered to run continuously on a 100% duty cycle and is rated to operate at maximum power (full voltage, full current output).

The true bipolar circuitry used by Arbin eliminates the switching time between charge and discharge. It also increases the longevity of equipment since relays are not switching during test profiles with frequent charge/discharge such as drive profile simulations.

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Evaluating Battery Test Equipment 3: Temperature

October 12, 2018

Temperature variance of the test equipment and the device under test will always affect the measurement. This is a physical property that cannot be escaped, but it can be minimized.

Current -vs- Time plot

Knowing how temperature affects the measurement empowers the researcher when determining the experimental error. When test equipment resolution and precision are sufficient, measurement fluctuation due to temperature will be seen. Gradual temperature changes will gradually skew results data [above], and sudden temperature changes can cause jumps in the data as seen [below]. It is important to use test equipment that is resistant to temperature changes with proper thermal control mechanisms and to control temperature of the test environment.

Translating this into test results...
Arbin defines the affect of temperature on the instrument accuracy as ~0.000185% / 1°C, by using patented shunt designs and high-quality materials that are resistant to temperature fluctuations. Additionally, some of Arbin’s test equipment uses internal thermal control mechanisms that isolate sensitive components and tightly regulate the temperature using techniques developed during a multi-year investigation with partners Ford Motor Company and Sandia National Lab’s metrology department; regarded as one of the best in the world. This technology allows the test equipment to maintain incredibly high precision measurements.

Current -vs- Time plot

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Evaluating Battery Test Equipment 2: Precision

October 12, 2018

Precision determines the level of noise/fluctuation present in the test equipment’s measurement. Precision also indicates the consistency and repeatability of the instrument’s measurement circuitry. A measurement with very little noise/fluctuation is considered to be precise. Measurement precision at “100ppm” indicates it will vary by no more than 0.01% (100/1,000,000).

Many instruments will not specify their precision, which is a warning sign, or will improperly report precision though multiple averaged calculations or very slow frequency data logging that hides the noise. Another common tactic is to report precision of battery coulombic efficiency calculations instead of hardware specification. These practices are misleading and reflect negatively on the company’s reputation. [Ask to learn more.]

The test equipment resolution, quality of materials, and thermal management all play a significant role to provide superior precision. Precision should be specified directly for the voltage, current, time, and sometimes temperature measurement of the test equipment.

Translating this into test results...
Arbin defines the measurement precision for voltage, current, and time for each class of test equipment. These are the three parameters measured by the test equipment that define its performance. Quartz timing crystals are used for measurement and timestamp; representing the state-of-the art method for such measurements.

The benefits of high-precision measurements during battery research have been widely discussed in academia for almost a decade. Coulombic efficiency and differential capacity are two metrics that have been shown to require incredibly high precision test equipment to be meaningful and draw confident conclusions. These analytical techniques can miss or obscure signatures in the data if experiments are conducted with low precision test equipment that will generate noisy and inconsistent (unrepeatable) results.

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Evaluating Battery Test Equipment 1: Resolution

October 12, 2018

Resolution indicates the smallest change in measurement that can be detected by the instrument’s sense and control circuitry. Typically referred to in “bits” of resolution or an absolute unit of measurement such as µV or µA.

For battery test equipment, resolution is determined by the analog to digital and digital to analog conversion, commonly known as ADC and DAC, of the sense circuitry and control system. Analog signals vary at a continuous (near infinite) rate while a digital signal varies by a discrete rate that is measured in bits. When zooming in to look at current/voltage/time measurement data, the bits of resolution are the smallest changes that can be detected, and while capacity, energy, internal resistance, etc. are not direct measurements, they are all calculated from the same data.

Translating this into test results...
Arbin’s 24-bit resolution means its circuitry can sense 1 part in 16,777,216 (2^24). This is a 256x improvement over 16-bit resolution (1 part in 65,526), which is the industry standard. Greater resolution produces greater clarity with more significant digits. Higher resolution test equipment, when combined with high precision measurements, has the sensitivity to detect changes in voltage & current (as well as capacity, energy, IR, etc.) that would otherwise be missed, such as detecting a small spike in resistance as a battery approaches end of life, or a slight dip in coulombic efficiency that indicates end of life. Many academic papers have been published by scientists who look for trends and identifying test metrics that can reduce the test time required during battery material development. An upgraded tool with better resolution and overall performance should expedite this process even more.

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Customer Spotlight – Bureau Veritas

March 21, 2018

Bureau Veritas provides battery testing services on behalf of retailers who need to make confident decisions when selecting a battery manufacturer for their product. Retailers are faced with questions related to battery quality and performance, as well as analyzing how different types of battery may affect the performance of their product. Bureau Veritas provides the data necessary to make these decision by running simulations to compare batteries from different suppliers and different cell formats.

Their Arbin battery tester allows Bureau Veritas to provide the following services:

Testing to NASI C18.1M for different discharge profiles.
Capability to test different sized commercial batteries such as AA, AAA, C, D, 9V, and others.
Compare supplier's battery performance against national brands.
Test results include both numeric data and plots to provide a better understanding of performance and comparison between cells.
Comparison data helps retailers invest in the best battery and supplier for their products.

Contact Bureau Veritas for more information on their Battery Testing services.
Tel: 1-800-277-3300 or +1 716-505-3300
Email: info@us.bureauveritas.com
Bureau Veritas Battery Testing

Marketing Opportunity

February 13, 2018

Arbin invites all of you who use Arbin test equipment to tell us about your recent or upcoming achievements, results, products, and successes! We want to celebrate your success and share across the industry through our e-newsletter, or other possible co-marketing opportunity. These "customer spotlights" are the most commonly requested news item we share.

Place your accomplishments in the inbox of industry professionals around the world. Our e-newsletter reaches an extensive audience across the energy storage industry from academic researchers to large-scale manufacturers. Please contact marketing@arbinmail.com or your sales representative to learn more. We look forward to hearing from you!

Snow!

December 18, 2017

Pardon our excitement, but it snowed in central Texas, y'all! It melted less than 18 hours later, but it was beautiful while it lasted. All of us here at Arbin wish you a Merry Christmas and Happy New Year!

See Arbin at 2017 The Battery Show (Booth 2010)

September 7, 2017

Arbin Instruments is exhibiting at The Battery Show in Novi, Michigan

(Tuesday-Thursday, September 12-14).

Come check out our great demo and visit with us to learn more about our new High Precision testing instruments capable of meaningful coulombic efficiency measurements.

Helpful PDF Event Resources

Download The Battery Show Event Schedule

Download The Battery Show Exhibitor List

Learn More about General Battery Testing
Cells / Modules / Packs

Learn More about High Precision HPC Testing on Cells up to 200A

Request a Quote

High Current Cylindrical Battery Holder

May 23, 2017

Tesla and Panasonic’s recent announcement of the new 2170 format cell has sparked renewed interest for an easy-to-use cell holder intended for high energy density and high capacity cells. Most industry available battery solutions cannot handle the high current delivered from the cylindrical format cells. Arbin’s recently redesigned High Current Cylindrical Battery Holder provides a perfect solution for currents ranging from 5A up to 200A. The battery holders are designed to provide an economic solution, allowing for quick setup and connection to Arbin’s battery test equipment or other testing assemblies. We are now accepting pre-orders for the first round of deliveries by September 2017.

The new 2170 format battery cells are capable of holding more raw materials and providing consumers with longer battery life. In addition to Tesla and Panasonic, Samsung and several other battery manufacturers are already beginning to move towards the new format and will soon begin production. Arbin’s High Current Cylindrical Battery holder is perfectly designed to work with the 2170, or 21700, cell with the dimensions of 21 millimeters in diameter and 70 millimeters long.

Arbin’s High Current Battery Holder allows the user to quickly connect and disconnect the device under test, eliminating the down time associated with previous commonly used connection methods. This specialized holder accommodates testing applications with a maximum current ranging from 5A up to 200A, lengths ranging from 10 mm to 120 mm, and a diameter of 10mm to 35 mm. The reengineered battery holder has adjustable contact probes, along with a single, spring lever mechanism to provide secure contact to the battery resulting in very low contact resistance and no damage to the device being tested. By having low contact resistance, the end user does not have to worry about the destructive high temperatures that usually develop in conjunction with high resistance to the current flow.

Please contact Arbin if you are interested in trying the new High Current Cylindrical Battery Holder. We are now accepting pre-orders for the first round of deliveries by September 2017. Click here for more details on ordering.

Arbin offers a complete collection of individual battery holders, trays, and racks for all types of cell: [LEARN MORE]