Summary
- Custom designed battery test system for production line quality assurance.
- User-friendly operator interface.
- Improved product conformity, traceability and reporting.
- Increased operational efficiency and reduced cost of quality assurance.
- Extensible solution to accommodate future requirements.
Background
Powervault is a British company, headquartered in London. It develops and manufactures the UK’s first fully-integrated solar energy storage system for the home, which stores free renewable energy from solar panels during the day and releases it in the evening when household energy demand peaks.
The Challenge
Powervault stores electricity in customers’ homes using either Lithium-ion Phosphate cells or Lead Acid batteries. The Lithium-ion Phosphate cells can store 2kWh – 6kWh of usable (AC) energy and the Lead Acid batteries can store 2.5kWh – 4kWh of usable (AC) energy.
As part of its quality assurance process, Powervault wished to create a test rig integral to its production facility to ensure all units perform as required – charging, discharging and storing charge within the specified parameters.
Austin Consultants were asked to provide an Automated Test System capable of being able to charge, discharge and monitor tests on six battery packs simultaneously. Each test involved sending RS232 commands to a Charger/Inverter unit to tell the system what the desired charge/discharge value was. Whilst doing this I2C commands would be sent directly to the battery pack to query the Voltage, Current and Temperature within the battery pack itself.
Finally, the Voltage coming out of the physical battery also needed to be monitored.
Each test needed to be configured by an operator and left to run whilst the values recorded and current test steps are displayed on a User Interface and logged to file.
The Solution
The Austin Consultants team chose to use National Instruments (NI) TestStand to provide the flexibility required to meet Powervault’s need to run multiple simultaneous test sequences. TestStand was chosen for this project as it provides a modular environment that is adaptable and easy to configure. Each test has its own dedicated sequence and can cycle through each charge/discharge phase independently without the need of any operator interaction.
By designing a state handler in LabVIEW each test sequence can call its own dedicatedLabVIEW clone. This enables multiple individual test panels to be displayed to the operator at any one time – displaying measurements of the particular unit under test (UUT), the duration of the test and what test state it is in.
The LabVIEW environment is in charge of sending down the commands and receiving the responses from devices being communicated with. The LabVIEW code is architected in such a way that each element of the test is modular. There is a separate software module for RS232 comms, I2C comms, USB DAQ, user Interface etc.
Results
Powervault now operates an efficient Automated Test System capable running simultaneous tests on up to six batteries at any time. The operator is able to quickly see the measurement values of the test, the stage at which that test is at and if it has breached any error limits set by the operator. As all data is saved to a Test specified log file, therefore, anything missed at the time can be reviewed at the end of the test.
All of this is made possible by using a combination of NI Software and Hardware. We were able to utilise the ability to structure a test using the power of TestStand merged with the data acquisition and data handling capabilities of LabVIEW and DAQmx.
As a cycle can last up 24 hours, the new automated rig allows tests to be configured, left to run and all data captured, without the need for any manual intervention, reducing both the cost of testing and potential for operator error.
