9th April 2020
Quality Assurance and Testing for ION’s BMS
The Design Phase
A Battery Management System (BMS) has two broad functional blocks namely – the hardware & the firmware (or the software) that work in unison to keep the battery safe and extend its life. When the hardware is designed and manufactured, the firmware makes the board functional as per the applications and requirements. Quality Assurance (QA) and Testing are the most important phases in the product lifecycle since the success of this phase dictates the level of safety and the management of the battery’s life.
The Hardware is designed as per the requirements of the customer’s application – Electric Mobility and/or Energy Storage Systems. Based on the requirements, a prototype is designed.
Once the design is finalized, it is sent to the vendor and the prototypes are validated for their basic functionalities. The prototypes are further optimized based on the functionality and additional features that develop the hardware.
When all the modifications are completed, the BMS is validated for its functionalities at different environmental conditions. Based on the data collected in the previous step an ‘operating range’ is defined.
The Firmware follows a similar sequence. Software is developed for the essential functionalities of the BMS. The requirements of the customer/system/hardware are built over the essential functionalities.
The software is tested on the prototype BMS hardware. Based on the outcomes and new requirements, the iterations are made to tailor the firmware for its optimum performance and management of battery life and safety.
Once the desired results are obtained, the firmware is finalized and deployed in the BMS.
As soon as the hardware prototypes and the firmware are ready the boards are sent for EMI/EMC testing to external independent laboratories. Once the boards are tested, they may need further modifications based on the outcomes of this stage. Once the EMI/EMC test is cleared, the hardware and the firmware are again validated, and the design is finalized.
Quality Assurance & Testing for BMS PCB Fabrication
The first stage of the manufacturing process is the fabrication of the PCB (without any components). The priority is to ensure that the layout remains true to the design while working with the restrictions for board edge clearance, drill holes and the space between the pads, traces, and other elements. To ensure these issues are addressed, ION performs the following tests:
- Design for Manufacturing (DFM) – ION ensures that the DFM released to the vendors is accurate concerning the board design. Any violation that takes place is rectified before the board is manufactured.
- Automated Optical Inspection (AOI) testing is more reliable than manual visual inspection. AOI testing helps identify the following problems:
- Line width
- Excess copper
- Missing elements
- Shorts circuits
- Cut traces or pads
- Drill hole breakage
The Manufacturing & Operations Phase
The next phase of the product lifecycle is the Operations and Manufacturing phase. While the PCBs are being designed and fabricated, components for the BMSes are procured. Once the components are shipped by our verified manufacturing partners the BMS goes in for manufacturing.
Quality Assurance & Testing for BMS Component Procurement
Component procurement quality assurance begins with component selection. Our team hand-picks the components depending on the BMS requirements.
Generally, the quality of components guides the selection process. The components are procured from verified global suppliers and are RoHS (Restriction of Hazardous Substances) compliant. This stage of the BMS lifecycle requires good QA checks since delays can stall the manufacturing process. Hence, we keep optimizing the process to procure the right components as fast as possible.
To minimize such problems ION strictly follows the following testing and validation processes:
- Bills of Materials (BOM) Validation – These checks are done to ensure the components in the BOM match the BMS design.
- Manufacturer Part Number (MPN) Verification – At ION we take extra care while verifying the MPNs. If the MPN is incorrect it can result in the procurement of the wrong component. A single incorrect digit can result in a drastically wrong component. Such an error will result in the loss of time and potentially add extra cost.
- Component Reference Designator Verification – This is the unique identifier for the number of components to be acquired in the BOM.
- Component Manufacture Status Checking – This ensures that the component will be available for future production.
- MPN-Footprint Match – This step ensures that the footprint of the BMS design should match the MPN since an error here will result in a mismatch for the solder relief and component spacing and will result in the pausing of the assembly line.
- Partner with Reliable Suppliers – All our manufacturing partners have a strong supply chain process, are highly reliable and are verified by ION
- Documentation Review – Documentation of the components shipped is scanned thoroughly for review and potential errors.
- Visual Inspection – This helps ensure that the component matches your order and documentation.
- Component Tolerance Check – This is one of the most important checks as we test the BMS components to match the threshold that ION had set in the datasheets for a specific application.
These tests are performed during the prototyping stage as well.
Quality Assurance & Testing for BMS Assembly
In the final stage of the manufacturing process, the Design for Manufacturing (DFM) files are used for the component assembly process. Testing is necessary to avoid any incorrect component placement issues. Testing during this stage is typically more intensive than during the fabrication phase.
Some quality assurance techniques that are performed after the BMS is assembled include:
- Visual Inspections – As performed earlier, these are also done at this stage of the product lifecycle to check for excess solder, issues in components and other problems that require modifications.
- X-ray Inspection – Provides non-invasive, high-quality imaging of the BMS’s internal quality thereby unearthing any shorts between the pins of the ICs.
- AOI – During assembly, higher quality imaging is used to thoroughly check the connections and solder quality. It also verifies the component orientation.
After the boards are ready, they also go through a process of Conformal Coating. Conformal coating is a protective coating or polymer film 25-75 µm thick (typically 50 µm) that ‘conforms’ to the circuit board topology. Its purpose is to protect electronic circuits from harsh environments that may contain high humidity, airborne contaminants, and varying temperatures. The boards are then sent to ION for quality checking & functional testing.
Once the boards arrive, every single board is visually inspected for any manufacturing defects. After the initial inspection, the BMSes are tested for their functionalities by a process called End-of-Line (EoL) testing.
End-of-Line Testing (EOL)
End-of-Line Testing measures and checks the functionality of ION’s battery management systems. The key factors taken into consideration at ION are high test quantity, test completion and low system with upgrade costs. At ION, we have built an automated testing platform called the ION Testmaster.
The homegrown ION Testmaster is built specifically for performing automated Functional Circuit Test (FCT) on ION’s BMSes.
Function Circuit Test (FCT) checks the performance and the functionality of the BMS board for every function at the hardware level, and also ensures that a fully operational BMS has reached the customer. It is generally performed in the final step of testing, under the End-of-Line testing, before shipping it to our customers. The Testmaster benefits ION’s BMSes by simulating the operating environment of the Device Under Testing (DUT) and by providing automatically generated reports for each BMS tested.
In the latest update, the ION Testmaster is interfaced with Edison Analytics for accurate and real-time inventory management using the MNP/serial number of the DUT, in this case, the BMS.
The Testmaster increases the number of boards tested in a given time frame, resulting in the reduction of efforts and the time-to-ship to an OEM for testing and debugging.
BMS Assembly – Ready to Deliver
After every EoL, a report is generated for every BMS tested. The ION Testmaster accelerates high volume testing to help the BMSes reach our customers faster. Once the boards have gone through EoL Testing they are packed in anti-static bags and shipped to the customer with the relevant reports.
ION ensures that the highest quality of materials is used for our BMS boards. The quality assurance measures taken during the complete lifecycle of all our products help meet the functional criteria of the BMS boards.
Edison Analytics: Battery Intelligence & Analytics Platform2nd December 2020/