Today, advanced batteries are widely used in transportation, commercial industries, aerospace, and defense industries, as well as in portable electronic devices. They must be tested with high accuracy to ensure they operate properly. To perform these tests, some companies are using the AMETEK VTI Instruments EX1401 Isolated Thermocouple and Voltage Measurement Instrument. The EX1401's accuracy, isolation, and sampling rate make it an ideal choice for battery testing.

Isolation protects against common mode voltages

To increase battery life-cycle test throughput, multiple cells are connected in series during the charge and discharge cycles, and during the test, a voltage DAQ instrument measures the voltage across each battery. This process can create a high common mode voltage, and this voltage, combined with common mode noise, can cause the acquired data to become unreliable. Because the common mode voltage is high relative to the actual voltage of the batteries, it is difficult to distinguish between the noise and the actual battery voltage.

The EX1401 Isolated Thermocouple and Voltage Measurement Instrument provides up to 500V of channel- to-ground isolation in order to safeguard against high common mode noise. Each individual channel of the EX1401 is isolated and has exceptional input protection across a wide range of operating conditions. Not only does this ensure accurate measurements, it protects the instrument from harmful voltages.

High samples rates and temperature measurements

Slew rate is one of the most important performance specifications. To measure the slew rate, batteries under test are charged and discharged repeatedly while a voltage DAQ instrument measures the battery voltage. Using this data, engineers plot the battery discharge curve and calculate the expected battery life and number of charge/discharge cycles.

To create an accurate battery discharge curve, a battery test must measure battery voltage data at a high sample rate (at least 1 kSa/s) over a long period of time. In addition to measuring the battery voltage, the test must monitor the battery temperature to ensure the batteries do not overheat and cause damage when discharged quickly. Because temperature instruments generally do not support high voltage ranges and high sampling speed, however, voltage and temperature instruments generally have to be set up separately.

The EX1401 supports sampling rates up to 20 kSa/s, so capturing the voltage changes every millisecond is easy, and the batteries' slew rates can be calculated accurately. Each channel of the EX1401 is independent and software configurable. Each of the 16 channels can be configured to measure voltage on different ranges or temperature independently. It allows the engineer to use the same instrument to measure both required measurement types. As a result, it can increase the flexibility of the test, reduce the total cost of ownership of the whole system and save storage space. Furthermore, each channel is equipped with an individual 24-bit ADC. During the data acquisition process, data from all channels are synchronized. The EX1401 allows the engineer to connect and test multiple batteries at the same time, increasing the test throughput.

Free, turn-key software aids analysis

To analyze the data, AMETEK VTI Instruments supplies EXLab Express, a free, turn-key software package. EXLab Express provides a Microsoft® Excel-like channel configuration table that allows users to easily configure channels for voltage and temperature measurements. Once the channels are set up and the data acquisition process begins, the data can be monitored in various intuitive ways. Once a test is complete, users can play back the data using EXLab Express or export the data to another software package for further data analysis.

When combined with EXLab Express software, the EX1401 offers everything needed for battery testing. It provides 500V isolation to safeguard against common mode noise. It supports sampling rates up to 20 kSa/s to capture batteries' voltage changes on the millisecond level. It is also a flexible instrument that supports 16 software-configurable voltage and temperature channels, increasing the flexibility and throughput of battery testing, as well as decreasing total cost and storage requirements.