Battery testing on a universal testing machine (UTM)
Every lithium-ion cell depends on thin materials behaving mechanically the way the datasheet promises. A universal testing machine (UTM) qualifies that behaviour - separator tensile and puncture, copper and aluminium current-collector foil strength, electrode coating adhesion, and tab and busbar weld strength - so material is safe to wind, coat and cycle.
What is battery testing via UTM?
A universal testing machine applies a precisely controlled load - pulling, peeling, puncturing or compressing - while measuring force and displacement. In a battery, the parts that fail mechanically are thin and unforgiving: a 9-25 micrometre separator, a 6-20 micrometre current-collector foil, a brittle coated electrode, a welded tab. UTM testing converts "does this material hold up?" into numbers a QC team can sign off against.
Why mechanical data decides safety and yield
Mechanical weakness shows up in three expensive ways. Safety: a separator that punctures or tears too easily risks an internal short. Yield: a foil that breaks during high-speed coating or winding stops the line and scraps material. Reliability: an electrode coating that peels, or a tab weld that pulls apart, fails in the field. A UTM is how each of these is caught before scale-up.
The same frame, with different grips and fixtures, covers the whole bill of materials - which is why a UTM is the workhorse of battery incoming-inspection and R&D labs.
Where a UTM fits across the cell
One machine, six recurring jobs. Each card is a real test request from a cell, electrode or material manufacturer.
Separator film
Tensile strength and elongation in MD and TD, plus needle puncture resistance.
Aluminium foil (cathode)
Break load, tensile strength and elongation of the cathode current collector.
Copper foil (anode)
Tensile and elongation of thin, handling-sensitive anode current collector.
Coated electrode
180°/90° peel to measure active-coating adhesion to the foil.
Tabs & busbars
Tensile / peel pull testing of ultrasonic and laser-welded joints.
Pouch seal
Heat-seal strength and peel of pouch-cell laminate seals.
Battery separator testing, explained
The separator is the thin porous film that keeps the cathode and anode apart while letting ions pass. It is typically 9-25 micrometre polyolefin (PE/PP), often ceramic-coated. Because it is the cell's last line of defence against an internal short, its mechanical properties are safety-critical - and highly sensitive to direction, handling and fixture details.
Why separators are tested mechanically
During cell build the separator is unwound, tensioned and wound at speed. Too little tensile strength and it tears on the line; too little puncture resistance and an electrode burr or particle can pierce it; uneven MD/TD behaviour and it distorts the electrode stack. UTM testing quantifies all three so incoming rolls can be compared lot-to-lot and supplier-to-supplier.
Separators are also where a small change - a new coating, a thinner gauge, a new supplier - must be re-qualified before it reaches production. That is exactly the repeatable, low-force tensile and puncture work a UTM is built for.
| Separator property | UTM test | Primary reference |
|---|---|---|
| Tensile strength & modulus (MD/TD) | Strip tensile, film grips | ASTM D882, ISO 527-3 |
| Elongation at break (MD/TD) | Strip tensile to rupture | ASTM D882, ISO 527-3 |
| Puncture resistance | Needle puncture fixture | Customer-specified probe & speed |
| Mix penetration / handling strength | Compression / penetration setup | Confirm method per material |
Who builds battery materials in India - and what they test
Under the PLI scheme for Advanced Chemistry Cells, India is localising the lithium-ion value chain. As cells, foils and separators are made or finished domestically, the mechanical QC that used to sit overseas now sits in Indian labs. Below is the public ecosystem by role, with the UTM test each role needs.
Companies are listed as public industry context to illustrate the value chain - not as FITCO customers.
Cell & gigafactory makers
Examples: Ola Electric (cylindrical cells, Krishnagiri), Exide Energy Solutions, Amara Raja Advanced Cell Technologies (Telangana), Tata Agratas, Reliance New Energy, Cygni Energy.
What they test: incoming separators (tensile & puncture), current-collector foils (tensile), electrode coating peel, and tab/busbar weld pull - to protect line yield and cell safety.
Current-collector foil makers
Example: Hindalco - commissioned battery-grade aluminium foil capacity in Odisha for cathode current collectors; copper foil for anodes is an emerging area in India.
What they test: foil break load, tensile strength and elongation (ASTM E345) on thin, fragile foil that must survive high-speed coating and winding.
Separator makers & suppliers
Examples: Daramic (Asahi Kasei group) makes PE separators in India with stated lithium-ion separator plans; Li-ion separators are still largely imported from Asahi Kasei, Toray, SK and Sumitomo.
What they test: separator film tensile & elongation (ASTM D882 / ISO 527-3) and needle puncture resistance for QC and supplier comparison.
Electrode & active-material makers
Examples: Himadri Speciality Chemicals and Epsilon Advanced Materials (anode / specialty carbon and graphite).
What they test: coated-electrode adhesion via 180°/90° peel - confirming binder and coating bond to the current-collector foil.
How each material is tested on a Testometric UTM
Testometric (UK) universal testing machines - benchtop frames to around 5 kN with interchangeable low-force load cells and the right grips - cover the full battery-material menu. FITCO supplies, installs, calibrates and supports them across India.
| Maker / role | Product | Testometric UTM test | Reference | Fixture & load cell |
|---|---|---|---|---|
| Cell / gigafactory makers | Incoming separator film | MD/TD tensile + elongation; needle puncture | ASTM D882 / ISO 527-3 + customer probe | Film grips + 1 mm needle fixture, low-force load cell |
| Foil makers (e.g. Hindalco) | Aluminium & copper current-collector foil | Break load, tensile strength, elongation | ASTM E345 | Pneumatic / foil-friendly grips, low-force load cell |
| Separator makers (e.g. Daramic) | PE / coated separator film | Tensile, elongation, puncture | ASTM D882 / ISO 527-3 | Film grips, fine load cell, needle fixture |
| Electrode / material makers | Coated electrode (foil + active layer) | 180°/90° coating peel / adhesion | Customer / internal peel method | Peel fixture + roller/sled, low-force load cell |
| Pack / module makers | Welded tabs & busbars | Tensile / peel weld pull | Internal weld-strength method | Tab grips, alignment fixture |
Low force is a precision problem, not a power problem
Separators and foils break at tens of newtons. The hard part is resolving small forces cleanly, gripping fragile film without crushing it, and keeping alignment perfect. Testometric's UK-built frames take interchangeable low-force load cells and battery-specific grips and fixtures, so one system reads a 9 micrometre separator and a copper foil with the same confidence.
Standards: a starting point, confirmed per material
For separator films, ASTM D882 and ISO 527-3 are the first tensile references. For aluminium and copper foils, ASTM E345 is the most direct metallic-foil reference. Puncture is usually defined by the customer's probe, speed and report format. Final selection always depends on material, specimen geometry, speed and fixture.
Battery testing via UTM - common questions
Can a UTM test lithium-ion separators?
Yes - a low-force frame with film grips measures MD/TD tensile and elongation (ASTM D882 / ISO 527-3), and with a needle fixture, puncture resistance.
What force capacity do I need?
Battery work is low-force. A benchtop frame to ~5 kN with small load cells covers separators, copper/aluminium foils and coating peel. Load-cell resolution and fixtures matter more than max capacity.
Which standards apply?
ASTM D882 / ISO 527-3 for separator film; ASTM E345 for metallic foils; customer-defined methods for puncture, peel and weld pull.
Copper and aluminium foil too?
Yes - with pneumatic/foil grips and a fine load cell, a Testometric UTM measures break load, tensile strength and elongation per ASTM E345.
How are electrode coatings tested?
A 180°/90° peel test measures the force to lift the active coating from the current-collector foil - the standard adhesion check.
Can you supply the fixtures?
Yes - film grips, foil grips, peel sleds and needle puncture fixtures, matched to your material and confirmed method, supported in India by FITCO.
Related battery testing pages
Qualifying separators, foils or electrodes in India?
Tell us the material, thickness, direction, required standard and fixture expectation. FITCO will shortlist the right Testometric UTM, load cells and battery fixtures - and support installation, training and calibration.
Talk to a FITCO testing expert