Product Oct. 24, 2022

Prevents latent defective battery leakage that can cause fires. Battery insulation tester BT5525 Released.

HIOKI E.E. Corporation will release the Battery insulation tester BT5525 for battery production lines on October 24, 2022. The Battery insulation tester BT5525 is often used in production lines for LIB (lithium-ion battery) battery cells. It is a device to detect insulation defects that cause battery ignition or reduce longevity. Until now, it has been difficult to detect latent defects in battery cells, such as the presence of metallic foreign matter or small short circuits. The BT5525 solves these problems by introducing new functions and improving measurement performance.


EVs (electric vehicles) are currently being developed by automobile manufacturers around the world with the aim of achieving carbon neutrality. LIBs are widely used in the batteries that power EVs. To protect limited resources and reduce environmental impact, batteries are required to create new value in a circular economy. To work towards a recycling-oriented society, it is necessary to consider the entire life cycle of batteries. In the production of batteries, it is very important to maintain safe, reliable, and long-life qualities.

LIBs can store a large amount of electricity. However, once an internal short circuit occurs due to poor quality or deterioration, the high energy density of the LIB can lead to hazards such as ignition or abnormally high temperatures. Insulation resistance testing is essential for safe and long-life battery production to prevent internal short circuits by electrical measurement. To improve inspection quality in battery production lines, HIOKI has now released the BT5525 Battery insulation tester.


The insulation resistance test checks the hardness of electric current flow. The insulation resistance value is confirmed by applying a DC voltage to the measured object. If a battery cell is damaged or there is a work process error, the insulation resistance will be low, and the battery cell will be excluded as defective in the production line inspection.

However, if metallic foreign matter (small foreign matter such as electrode fragments) is present in the manufacturing process, the insulation resistance may not drop immediately and cannot be detected. Undetected contaminants are latent defects that can cause degradation and internal short circuits when the finished battery is in use for an extended period of time. It can even be a potential fire hazard.

The Battery insulation tester BT5525 reliably and quickly measures insulation resistance in battery cell production lines. Detecting latent defects contributes to improving LIB safety and assuring quality.

Product website


1. Unique detection method that does not miss metallic foreign matters - BDD function (Break Down Detect)

When measuring the insulation resistance of battery cells, the BDD function checks not only the value but also high-speed small changes in voltage and current. High-speed sampling at 5 MS/s (5 million times per second) and analog peak hold circuitry capture small changes in voltage and current to detect potential defects.

2. Contact check function to prevent false negatives

Defects in equipment or wiring can prevent the measurement terminals from making proper contact with the battery cells. Improper contact interferes with accurate insulation resistance testing and may result in defectives products falsely reading as good quality. The floating capacitance detection contact check function correctly determines contact with the test object, preventing defective products from escaping detection.

3. Optimal Cost Increases Productivity

The BT5525 offers high inspection quality at an optimal cost for battery production lines. It reduces time costs through high-speed inspections with 25 times the measured current compared to conventional systems. It also reduces space costs due to its compact form factor that allows for space-saving expansion. The cost reduction helps improve battery productivity, which is in increasing demand.

Main Applications

- Insulation resistance testing of battery cell production lines for LIBs
- Insulation resistance testing of finished battery modules