What Is Internal Resistance — UL 2580?
The internal resistance test determines the battery's internal resistance from the voltage drop under load or from AC impedance. Two approaches are used: DC-IR and AC-IR.
Purpose of Internal Resistance — UL 2580
The purpose is to assess the battery's power-delivery capability, check production consistency and monitor ageing.
Which Products Is Internal Resistance — UL 2580 Applied To?
- Lithium-ion cells
- Battery modules and packs
- Portable device batteries
- Energy storage cells
In Which Sectors Is Internal Resistance — UL 2580 Used?
Standards Related to Internal Resistance — UL 2580
- UL 2580Safety in electric vehicle batteries test
Internal Resistance — UL 2580 Conditions
- Method
- DC-IR (voltage drop under a pulse load) or AC-IR (1 kHz impedance)
- Pulse current and duration
- Current and duration defined in the standard for DC-IR
- charging status
- Measurement is performed at the defined SOC
- Temperature
- At the reference temperature; temperature markedly affects internal resistance
Equipment for Internal Resistance — UL 2580
- Battery test system (with pulse-load capability)
- AC impedance meter (1 kHz)
- temperature cabinet
- Four-wire measurement connection
Sample Requirements for Internal Resistance — UL 2580
- Measurement points and contact resistance must be checked
- The specimen must be brought to the defined SOC
- Temperature stabilisation must be completed
- A four-wire (Kelvin) connection must be used
Duration of Internal Resistance — UL 2580
The duration per measurement is short; temperature stabilisation determines the total time.
Internal Resistance — UL 2580 Procedure
- 1The specimen is brought to the defined SOC and its temperature is stabilised.
- 2A four-wire connection is set up.
- 3The 1 kHz impedance is measured for AC-IR, or the defined current pulse is applied for DC-IR.
- 4The voltage drop and current are recorded.
- 5The internal resistance is calculated and reported.
Internal Resistance — UL 2580 Acceptance Criteria
The acceptance criterion is given in the specification as a maximum internal resistance value. In ageing monitoring, a maximum increase ratio relative to the initial value may serve as the criterion.
Evaluation of Results
DC-IR and AC-IR values cannot be used interchangeably; the method must always be stated in the report. Temperature and SOC are recorded because they directly affect the measurement.
Internal Resistance — UL 2580 Report
- Applied standard and method (DC-IR / AC-IR)
- Pulse current and duration, or measurement frequency
- SOC and temperature
- Measured internal resistance values
- Connection arrangement
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- EU Battery Regulation
Batarya Testleri — What Does This Testing Field Cover?
The section below describes the field that the Internal Resistance test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Battery testing answers three separate questions, each with its own body of standards: can the battery be transported, is it safe in use, does it deliver the declared performance? These three questions are often confused with one another, and the confusion has commercial consequences — a market cannot be entered with a transport report, and a shipment cannot be made with a product safety report.
On the transport side, UN 38.3 is a mandatory gate; a battery without that evidence cannot be shipped. On the safety side the application determines what applies: IEC 62133-2 for portable products, IEC 62619 and IEC 63056 for industrial and energy storage applications, UNECE R100, UL 2580 and ISO 6469 for electric vehicles. On the performance side, capacity, internal resistance, cycle life, self-discharge, charge acceptance and temperature-dependent behaviour are measured.
The distinction of LEVEL is essential in this family and is the subject that causes the most argument in the supply chain. Cell, module and pack are assessed separately; a certificate obtained for a cell does not demonstrate the conformity of the pack. Alongside the cells, the behaviour of the pack is determined by the battery management system, the cooling design, the mechanical structure, the interconnection arrangement and insulation coordination. Putting the cell supplier's report into the pack file is a common but inadequate approach.
Thermal runaway and its propagation are the most critical subject in the field. A lithium cell may enter a self-sustaining chemical reaction when damaged or overheated; at that point removing the heat from outside is usually not possible. Modern standards therefore treat thermal runaway of a single cell as an UNAVOIDABLE fault scenario and change the question: does the event propagate to neighbouring cells, what does it release outside the pack, and how much time is left for the user to escape?
In this field the battery management system is assessed not as an electronic board but as a SAFETY FUNCTION. It is shown that overcharge, overdischarge, overcurrent and overtemperature protections actually operate, that the system falls to the safe side in a fault, and that its software has been verified. In industrial and vehicle applications this assessment is tied to functional safety frameworks.
The regulatory side is becoming rapidly more demanding. Battery Regulation (EU) 2023/1542 goes beyond safety and introduces obligations for carbon footprint declaration, recovered content ratio, durability and capacity declaration, the battery passport, and removability for portable batteries. This takes the scope of testing beyond classical safety tests.
Method groups in this field
Electrical abuse
Overcharge, overdischarge, external short circuit, forced discharge and unbalanced charging. This is where it is seen whether the protection circuits actually work.
Mechanical abuse
Vibration, shock, crush, penetration, free fall and tipping. It is monitored whether internal short circuit conditions arise.
Thermal tests
Temperature cycling, thermal shock, high temperature storage, fire exposure and thermal runaway propagation.
Environmental tests
Humidity, low pressure, salt spray and, where required, immersion; these come to the fore in vehicle and outdoor applications.
Performance measurements
Capacity, energy and power, internal resistance, efficiency, cycle life, calendar life and temperature-dependent behaviour.
BMS verification
Verification of protection thresholds, the cell balancing function, communications and fault response.
Commonly confused in this field
- UN 38.3 is not a product safety certificate; it only demonstrates transport conformity.
- A cell certificate does not demonstrate pack conformity. The pack is assessed separately with its own architecture.
- Two packs built from the same cell give different results; cooling, interconnection and mechanical structure are decisive.
- A performance test is not a safety test. A cycle life report does not satisfy safety requirements.
- For an electric vehicle battery, a UL 2580 report and UNECE R100 approval are not the same thing; one is a standards assessment, the other a type approval regime.
- A vehicle battery moved into a second-life application enters a new usage profile; the earlier assessment does not carry over directly.
Which decisions these results support
- Transport conformity and the test summary for shipment
- Product safety declaration and market access
- Performance, durability and carbon footprint declarations under the Battery Regulation
- Assessing the impact of a cell supplier or BMS change
- Site acceptance processes for an energy storage system
Related Tests
Frequently Asked Questions About Internal Resistance — UL 2580
Why do DC-IR and AC-IR give different results?
AC-IR is generally measured at 1 kHz and captures the ohmic component. DC-IR also includes polarisation effects depending on the pulse duration, so it is typically higher. The two are reported separately.