Samsung says faulty batteries caused Galaxy Note7 to catch fire

After several reported cases of catching fire, Samsung discontinued the Galaxy Note7 and recalled three million shipped units of the handset. Now after several months of in-depth investigation, the South Korean tech giant has finally revealed the reason for Galaxy Note 7 to catch fire.

And as expected, the faulty batteries were blamed for the Galaxy Note7 fiasco. The company used batteries built by two suppliers: Samsung SDI referred to as Battery A and Hong-Kong based Amperex referred as Battery B. Based on detailed analysis of the affected batteries, Samsung found separate issues with both Battery A and Battery B.

Battery A assessment

I. There may be multiple contributing factors relating to battery assembly/manufacturing and design that when combined led to the failure of the Note 7 in the field
A. Battery assembly/manufacturing:
• Deformation at the upper corners
B. Battery design:
• Thinner separator could lead to poorer protection and reduced tolerance to manufacturing defects
• Higher energy density in general can exacerbate the severity of a battery failure
II. One major failure mechanism is likely:
A combination of deformation at the upper corners + thin separator + repeating mechanical stresses due to cycling, causing higher possibility of separator damage leading to an ISC between aluminum and copper foil at the corner
III. Additional investigation is needed to understand the root-cause of the deformations at the upper corners

Battery B assessment

I. No evidence of device-level compatibility issues that may have contributed to the failure of the Note 7 in the field
II. There may be multiple contributing factors relating to production quality and battery design that when combined led to the failure of the Note 7 in the field
A. Production quality:
• Missing insulation tape on tab could result in higher possibility of ISC
• Bigger protrusion of welding points in tab could lead to higher possibility of separator puncture
• Misalignment of insulation tape and/or tab could bring more risk of ISC
B. Battery design:
• Thinner separator could lead to poorer protection and reduced tolerance to manufacturing defects
• Higher energy density in general can exacerbate the severity of a battery failure
III. One major failure mechanism for field incidents is likely:
The combination of (1) missing insulation tape + (2) sharp edged protrusions on tab + (3) thin separator, all leading to a high possibility of an ISC between cathode tab and anode, subsequently resulting in heating and fire
IV. Further analysis is needed to understand the root-cause of the damage to the edge/corner of the battery which results in ISC at that location

For the investigation Samsung utilized around 700 researchers and engineers for testing over 200,000 Galaxy Note7's and over 30,000 batteries. The company also reveled that three million units of Galaxy Note7 were sold and 96 percent of those have been returned so far, while 120,000 units are still being actively used.

The company also announced that it has now implemented strict quality assurance protocals across the development process in order to renew its commitment to safety. Samsung has now designed an eight-point battery safety check to make sure this kind of problem will not affect any Samsung smartphones in the future. The measures include durability test, visual inspection, X-Ray and charge/discharge test.

Kaiser Bey

Kaiser is a tech enthusiast who likes to write, read and talk about tech. He dreams of going to Mars and never come back. We hope that you find his posts on AndroGuider helpful and informative