Electric Battery Quick Connect Fixture for Thermal Chamber Battery Testing

The Challenge

A global company was ramping up its electrification program and needed an easier way to test the lifespan of their electric batteries. They had been welding the tabs to the battery terminals that connected to the cycler. However, the process proved time-consuming and costly. The welding rendered the batteries useless for any future testing or use, contributing to the cost of the test program.

Before coming to ACS, the company had been working through a new design concept to resolve these test issues. The design concept was to design and build a fixture that held the batteries and could get easily inserted into the test rack. However, using a fixture to hold the batteries in place during testing created a new problem – increased contact resistance, which interfered with accurate voltage readings and artificially degraded battery performance.

Unable to resolve the issue, the company came to ACS for help with the design. The complete test unit had to fit within a small thermal chamber, maintain low contact resistance, and provide consistent performance. The process of switching out units under test also had to be easy and efficient.

The Solution

With the company’s design concept for an electric battery quick connect fixture, we conducted an iterative design process creating fixture prototypes.

Our ultimate design was a fixture that contains a holder and spring-loaded terminals. The holder design is battery specific, which allows the fixture to secure the battery into a flat, optimal position, ensuring smooth contact with the terminals that link to the cycler via cables. It also allows the fixture to work with holders designed for other batteries within a certain size range.

Batteries expand under testing, which affects their performance. To prevent expansion, we added metal plates to the holders to compress the battery under testing. The metal compression plates sit in the plastic cradle that isolates the battery and the electrical connection points to the terminals.

To minimize the impact of contact resistance, we designed the fixture so the voltage-sensing terminals connect directly to the battery as a separate electrical circuit, minimizing the current flow and its related interference. By separating the voltage measurement system from the current measurement, we minimized contact resistance and lowered induced errors in voltage measurements, achieving superior accuracy in test results.

Our design also had to accommodate the limited space within the thermal chamber for battery testing. The electric battery testing system uses thick cables that don’t bend well in the small space. The tension from the thick cables makes it difficult to maintain flat surface contact with the terminals. We moved the connection point of those cables to a fixed point on the fixture that could stay in place, causing no interference with the optimum positioning of the fixture terminals when connecting to the unit under test.

The Outcome

Through collaboration between our team and the company, we refined the design until it minimized contact resistance so testing met the desired performance standards and fit into the compressed space.

The ultimate electric battery testing system design produced a framework where each battery is easily slipped into the quick connect fixture, which gets inserted into the holder. By turning one lever approximately 90 degrees, the fixture is raised putting the battery into contact with the free-floating terminals, creating a flat, level surface for best possible contact.

We delivered six electric battery quick connect fixtures for testing and development, each able to hold two batteries for concurrent testing.

With ACS expertise and creativity, the team engineered an innovative solution that lowered testing costs, while speeding up the testing process and improving the accuracy of the test results.

Key Features

• Designed a battery-specific electric battery quick connect fixture in order to secure the battery into the optimal testing position
• Minimized contact resistance and lowered induced errors in voltage measurements so testing met the desired performance standards
• Accommodated to the limited space within the thermal chamber for battery testing

ACS Services

• Engineered, designed, and manufactured electric battery quick connect fixtures
• Engineered a solution to lower testing costs and speed up the testing process
• Integrated equipment into current test facility