Battery Visual Inspection Overview
1. Purpose
To standardise the methods and criteria for inspecting the appearance of our products during production and dispatch.
2. Scope of Application
Applicable to polymer lithium-ion batteries supplied by VTC POWER CO., LTD, unless the customer has specified otherwise.
3. Responsibilities
Quality Management Department: Responsible for formulating and updating visual inspection standards, and for coordinating with other departments to resolve quality issues. OQC/Production Department Visual Inspectors: Responsible for conducting inspections in strict accordance with standards, and for reporting any quality issues identified during inspections.
4. Definition
As there is considerable flexibility in visual inspection, the textual descriptions of visual defects provided in this document are for reference only. During inspection, judgements must be made by referring to physical samples; where necessary, an MRB review must be conducted, and the results of that review shall prevail;
This Battery visual inspection criteria page explains Polymer cell quality control requirements for appearance inspection, OQC inspection, and MRB review decisions.
Use this VTC Power battery quality manual to understand how to inspect lithium polymer batteries, define battery surface defect specifications, and keep battery appearance inspection results consistent during production and outgoing quality checks.
Visual inspection of viewing angle and distance
The viewing angle and distance during inspection shall be determined as follows: (1) The light source shall be positioned directly above or to the side above the product; (2) The line of sight shall be perpendicular to the surface of the product, with the eyes maintained at a distance of 30-45 cm from the product; (3) During inspection, the product may be rotated 10 degrees around a 45-degree tilt axis for observation.
Test method: by eye and touch
There is a slight amount of gas inside the cell; there is a noticeable gap between the packaging film and the cell body, and when pressed flat by hand, the packaging film rises again and does not adhere tightly to the cell body.
AC =0
Test method: Measurement using gauges, visual inspection, manual inspection
Small indentations on the surface of the battery cell packaging film caused by pressure from a hard object; where there are four or more such indentations, the distance between them is less than 5 mm, the depth of the indentations is clearly detectable to the touch, or there are signs of damage to the packaging film.
AC =0 AQL value = 1.0
Test method: Measurement using gauges, visual inspection, manual inspection
The surface of the battery cell packaging film shows distinct indentations caused by pressure from a hard object; the indentations are longer than 10 mm but do not exceed one- third of the battery cell’s width; or the packaging film has been damaged as a result of the pressure.
AC =0 AQL value =1.0
Test method: Measurement using gauges and visual inspection
The area of electrolyte contamination exceeds 10 mm in diameter and covers more than one-tenth of the cell surface; there are two or more contaminated areas (or the packaging film shows obvious signs of blackening and corrosion). The area affected by electrolyte contamination must not exceed 10 mm in diameter and must not cover more than one -tenth of the cell’s surface; there must be fewer than two contaminated areas, and the packaging film must show no obvious signs of blackening or corrosion.
AC =0 AQL value =1.0
Test method: Measurement using gauges, visual inspection, manual inspection
Scratches on the surface of the battery cell packaging film; where the length of a scratch exceeds 5 mm and is greater than one-fifth of the battery cell’s width, the number of scratches is three or more, and the depth of the scratches is clearly detectable to the touch. Scratches on the surface of the battery cell packaging film, provided that the length of each scratch is less than 5 mm and less than one-fifth of the battery cell’s width, and there are fewer than three scratches.
AC =0 AQL value =1.0
Test method: by eye
A burnt tab caused by an external short circuit in the tab.
AC =0
Test method: by eye
The battery cell has undergone significant dimensional changes due to over-discharge, internal micro-short circuits, external short circuits and other factors, resulting in cell swelling.
AC =0
Test method: Visual inspection Measurement using gauges
During cell sealing, the packaging film was not aligned properly, resulting in a discrepancy in the length of the packaging film at the front and rear of the cell after sealing (misalignment of ≥0.5 mm).
AQL value = 1.0
Test method: by eye
During the folding process for the first and second seals, the battery cells may fail to fold properly or suffer damage to the folded edges. (Defective cells may be released after rework has been successfully completed.)
AC =0
Test method: by eye and touch
There are signs that the battery cell packaging film has been punctured or scratched by a hard object.
AC =0
Test method: by eye
Batteries exhibiting severe skewing, distortion, ghosting or incomplete coding during the coding process; instances where the coded content cannot be clearly identified or does not match the order specifications—including cases where the coded content is partially skewed or misaligned—are all classified as defective. (Defective cells must be wiped clean and recoded.)
AC =0 AQL value = 1.0
Test method: by eye
Corrosion or oxidation of the tab caused by issues with the incoming tab material or delamination and leakage of the tab adhesive, rendering it unsuitable for tinning.
AC =0
Test method: Visual inspection Manual inspection Measurement using gauges
The presence of foreign objects inside the battery cell, where the number of foreign objects is three or more, the area of each foreign object exceeds 1×1 mm, the distance between foreign objects is less than 5 mm, or there are signs of damage to the packaging film. furthermore, the objects must not be sharp.
AC =0 AQL value = 1.0
Test method: by sight and smell
A phenomenon whereby electrolyte leaks from the battery cell due to damage to the packaging film or an opening in the seal.
AC =0
Test method: by eye
Fractures in the battery tabs (including cracks in the tabs).
AC =0
Test method: by eye
The exposed length of the tab adhesive is shorter than specified in the technical specifications or process requirements, resulting in direct contact between the aluminium or nickel tab and the packaging film. The exposed length of the tab adhesive is shorter than specified in the technical specifications or process requirements, but the aluminium or nickel strip of the tab has not come into direct contact with the packaging film.
AC =0 AQL value = 1.0
Test method: by eye
The exposed length of the tab adhesive exceeds the specifications or process requirements, thereby affecting processing or dimensional requirements. The exposed length of the tab adhesive exceeds the specifications or process requirements, but this does not affect processing, dimensional requirements or performance.
AC =0 AQL value = 1.0
Test method: Visual inspection Tensile tester test
False welds and cold joints occurring in the cathode tab nickel -plating process due to instability in the laser spot welding machine module.
AC =0
Test method: Visual inspection Tensile tester test
Excessive welding occurring during the nickel-plating process of the positive tab on the battery cell due to instability in the laser spot welding machine module.
AC =0
Test method: by eye
Uneven tabs may affect the welding quality of the battery pack and customer usage. (Tabs that do not affect welding or customer usage following rework may be accepted as special cases.)
AC =0
Test method: Visual inspection and manual checking Measurement with a calliper
The battery cell exhibits an S-shaped deformation, which is clearly detectable to the touch, and its thickness exceeds the specified tolerance. (Defective cells will be re-inspected following rework.) The battery cells exhibit an S-shaped deformation; there is no tactile sensation, and the thickness meets the process requirements. (Defective cells will be re-inspected following rework.)
AC =0 AQL=1.0
Test method: By eye With a calliper
The cell tabs are not centred, but are offset towards the positive or negative terminal; the tabs are crooked, which affects pack assembly and customer use. (Exception: processes involving off-centre tab positioning are excluded.) If the cell tabs are not centred but are offset towards the positive or negative terminal, or if the tabs are crooked, this does not affect pack assembly or customer use. (Exception: processes involving off-centre tab positioning.)
AC =0 AQL=1.0
Test method: by eye
If a battery cell is accidentally dropped during production or transit, causing it to become deformed, this poses a potential safety risk.
AC =0
Test method: by eye
After the cell’s tab has been burnt, the metal strip of the tab has not turned black, but the tab adhesive shows signs of uneven melting due to heat, and there is a risk of electrolyte leakage from the cell.
AC =0
Test method: by eye
Damage to the Teflon on the second seal head, or foreign matter adhering to the Teflon surface, can result in pitting or unevenness along the seal edge; this defect may cause abnormal leakage in the battery cell.
AC =0
Test method: by eye and touch
There is a slight amount of gas inside the cell; there is a noticeable gap between the packaging film and the cell body, and when pressed flat by hand, the packaging film rises again and does not adhere tightly to the cell body.
AC =0
Test method: Measurement using gauges, visual inspection, manual inspection
Small indentations on the surface of the battery cell packaging film caused by pressure from a hard object; where there are four or more such indentations, the distance between them is less than 5 mm, the depth of the indentations is clearly detectable to the touch, or there are signs of damage to the packaging film.
AC =0
Test method: Measurement using gauges, visual inspection, and manual inspection
The surface of the battery cell packaging film shows distinct indentations caused by pressure from a hard object; the indentations are longer than 10 mm but do not exceed one-third of the battery cell’s width; or the packaging film has been damaged as a result of the pressure.
AC =0
Test method: by eye and touch
There are signs that the battery cell packaging film has been punctured or scratched by a hard object.
AC =0
Test method: by eye
20 mm; there are two or more areas of adhesive residue (including two); however, these marks do not affect the dimensions of the battery cell, the area of each mark is less than 4mm × 2mm, there are fewer than two such marks, and the marks are transparent in appearance. Scratches on the surface of the battery cell packaging film, where the length of the scratch exceeds 5 mm and is greater than one-
AC =0
Test method: Measurement using gauges, visual inspection, manual inspection
Scratches on the surface of the battery cell packaging film, where the length of the scratch exceeds 5 mm and is greater than one- fifth of the battery cell’s width, the number of scratches is three or more, and the depth of the scratches is clearly detectable to the touch. Scratches on the surface of the battery cell packaging; the length of each scratch must be less than 5 mm and less than one-fifth of the battery cell’s width, and there must be fewer than three scratches.
AC =0
Test method: Measurement using gauges, visual inspection, manual inspection
by eye A burnt tab caused by an external short circuit in the tab.
AC =0
Test method: by eye
Cell swelling occurs when the volume of the cell changes significantly due to over-discharge, internal micro-short circuits, external short circuits, physical damage or similar issues.
AC =0
Test method: by eye
Any instances where the metal terminals on the protective plate are indented by 0.5 mm or more (inclusive) due to defective incoming materials or poor workmanship, or where such defects affect the customer’s use of the product. A condition where the metal terminals on the protective plate are indented by less than 0.5 mm, or where the defect does not affect the customer’s use, due to defective incoming materials or poor workmanship.
AC =0 AQL value = 1.0
Test method: by eye
During the folding process for the first and second seals, the battery cells may fail to fold properly or suffer damage to the folds. (Defective batteries will be re-inspected following rework.)
AC =0
Test method: Visual inspection Voltage, internal resistance Test
A condition where the protection board becomes detached from the battery cell at the weld point due to an unstable weld or weld spatter during the welding process between the protection board and the battery cell. (Defective batteries are re -inspected following rework.)
AC =0
Test method: by eye
Severe skewing, distortion, ghosting or incomplete printing on battery cells during coding. Instances where the printed content cannot be clearly identified, or where the printed content does not match the order specifications. (Defective battery cells are re-coded after the original print is wiped off.) Battery cells that exhibit slight skewing, distortion or ghosting during coding, provided that the printed text remains clearly legible and matches the order specifications.
AC =0 AOL值=1.0
Test method: Visual inspection Manual inspection Measurement using gauges
The presence of foreign objects inside the battery cell, where the number of foreign objects is three or more, the area of each foreign object exceeds 1×1 mm, the distance between foreign objects is less than 5 mm, or there are signs of damage to the packaging film. furthermore, the objects must not be sharp.
AC =0 AQL value=1.0
Test method: Visual inspection Manual inspection Measurement using gauges
1. Misalignment of spot welds and tab fractures in battery cells (including tab cracks). 2. Tab fractures at the nickel-plated area of the positive terminal caused by poor soldering, excessive soldering or inadequate black resin encapsulation.
AC =0
Test method: Visual inspection Caliper measurement Measurement using measuring instruments
During the application of adhesive tape to battery cells in the PACK assembly process, defects such as missed tape application, tape that is too long or too short by 1/10 or more of the total tape length, tape applied at an angle of 20 degrees or more, or defects affecting product dimensions due to poor tape application; or where the negative electrode trim is not fully covered.
AC =0 AQL value = 1.0
Test method: by eye
The protective plates are misaligned; the left and right protective plates are tilted, and the base plates of the protective plates appear to protrude beyond the main body of the battery.
AQL value = 1.0
Test method: by eye
The nickel strip on the tab extends beyond the pad, posing a risk of puncturing the aluminium-plastic film.
AC =0
Test method: by eye
During the PVC film blowing process, shrinkage of the PVC film causes the main body of the cell or the edges of the rubber moulding to become exposed. (Defective batteries are re-inspected following rework.)
AC =0
Test method: Visual inspection Comprehensive testing
The terminal wires have been inserted in the wrong order or upside down, which does not comply with the process requirements; there is no response during comprehensive testing.
AC =0
Test method: Visual tension gauge
The terminal wire and terminal head are clamped together, but the tensile strength does not meet the process requirements.
AC =0
Test method: Visual inspection Comprehensive testing
Soldering P+ to P- or P- to B- causes the protection board to fail or short-circuit. (May be released after rework has been approved.)
AC =0
Test method: Visual inspection Comprehensive testing
Excessive soldering time or excessive temperature during the soldering of the protection board caused components on the board to detach, resulting in the protection board failing.
AC =0
Test method: by eye
During the tinning process, tin beads adhere to the wires and the PCB. (Defective batteries are re-inspected following rework.)
AC =0
Test method: by eye
During spot welding, damage to the tabs caused by blow- outs resulting from the welding needle not being centred over the pad, or from the welding needles being of different lengths.
AC =0
Test method: by eye
Solder peaks may form during the soldering process, and there is a risk that these peaks may puncture the aluminium- plastic film. (Defective cells will be re-inspected following rework.)
AC =0
Test method: by eye
When securing heat-shrink tubing, the terminal or the tubing may be scorched or torn if the heat gun is set to too high a temperature or if the terminal wire is held too close to the nozzle.
AC =0
Test method: by eye
After the battery cells in the pack have been removed, the surface of the cells becomes wrinkled.
AC =0
Test method: by eye
The insufficient amount of tin applied failed to ensure the required smoothness and coverage of the tab, resulting in solder joint failure. (Defective batteries will be re-inspected following rework.)
AC =0
Test method: Visual inspection Caliper measurement Measurement using measuring instruments
A situation where the length of the positive and negative tabs varies beyond the specified tolerance range due to tab trimming or issues with the incoming tab material, and this has already affected the tinning or spot-welding operations on the battery pack (where the tab length is less than 5 mm).
AC =0 AQL value = 1.0
Test method: Visual inspection Caliper measurement Measurement using measuring instruments
by eye Deformation of the metal terminals affects assembly
AC =0
Test method: Visual inspection Caliper measurement Measurement using measuring instruments
Plug brands by eye Genuine Molex 78172 connectors are marked ‘MXL’; if the marking does not match, it is a counterfeit.
AC =0
Test method: by eye
After the battery tab has burnt, the metal strip of the tab has not turned black, but the tab adhesive shows signs of uneven melting due to heat, and there is a risk of electrolyte leakage from the cell.
AC =0
