How to Calculate Charge/Discharge Internal Resistance with NEWARE Battery Cyclers for Testing

Understanding and measuring internal resistance are among the most important aspects of battery testing. Whether you are working with lithium-ion cells, power batteries, or energy storage systems, knowing how to calculate the charge and discharge internal resistance helps you assess battery quality, performance, and overall health. This guide explains the complete process using NEWARE battery cyclers, following industry standards and simple step-by-step methods.

What is Battery Internal Resistance?

Battery internal resistance refers to the opposition to current flow within a battery cell. It is measured in milliohms (mΩ) or ohms (Ω) and directly affects how well a battery performs during charging and discharging.

Internal resistance consists of two main parts:

Ohmic resistance comes from the physical materials inside the battery, including electrode materials, electrolyte, current collectors, and conductive additives. This type of resistance responds immediately when current flows through the battery.

Polarisation resistance arises from electrochemical reactions during charge and discharge cycles. It includes charge transfer resistance and ion diffusion effects. This resistance becomes more noticeable during high-rate discharge operations.

Lower internal resistance means the battery can deliver higher currents with less voltage drop, better energy efficiency, and less heat generation. Higher internal resistance leads to energy loss, reduced power output, and shorter battery life.

Why Measuring Internal Resistance Matters

Internal resistance serves as a key indicator for several critical assessments:

Battery health monitoring allows you to track how a battery degrades over time. As batteries age, their internal resistance increases due to side reactions, electrode degradation, and SEI (Solid Electrolyte Interphase) film growth.

Quality control during manufacturing helps identify defective cells before they reach customers. Batteries with unusually high resistance may have production faults or material problems.

Performance prediction helps engineers understand how batteries will behave under real-world loads. Batteries with higher resistance show larger voltage drops during discharge, which reduces usable power.

State of charge estimation becomes more accurate when internal resistance is factored into calculations. Real-time resistance tracking can improve SOC accuracy significantly.

Understanding DCIR: Direct Current Internal Resistance

DCIR (Direct Current Internal Resistance) is one of the most commonly used methods for measuring battery internal resistance. It determines resistance by observing the change in voltage when different current levels are applied to the battery.

The basic formula for DCIR calculation is:

DCIR = (V₁ − V₂) / (I₂ − I₁)

where V₁ and V₂ are voltage readings at two different points, and I₁ and I₂ are the corresponding current values.

DCIR testing provides results that closely match real-world battery behaviour because it measures resistance under actual operating conditions. This makes it particularly useful for power batteries used in electric vehicles and other high-drain applications.

For compatible cycler options and advice on selecting the right platform for DCIR workflows, see Battery Cyclers Category.

IEC 61960 Standard Testing Method

The IEC 61960 standard provides a widely accepted method for measuring DCIR. Following this standard helps ensure your results are comparable with those from other laboratories and manufacturers.

According to this standard, the test procedure involves:

• First, discharging the battery at 0.2C (where C is the rated capacity of the battery) for 10 seconds and recording the voltage (V₁) and current (I₁).
• Then, immediately discharging at 1C for 1 second and recording the voltage (V₂) and current (I₂).

DCIR is then calculated using the same formula:

DCIR = (V₁ − V₂) / (I₂ − I₁)

For example, if you test a 2,500 mAh battery:

• 0.2C corresponds to a 500 mA discharge for 10 seconds
• 1C corresponds to a 2,500 mA discharge for 1 second

This method balances measurement accuracy with minimising polarisation effects during testing. Explore IEC-aligned cycler configurations and accessories here: NEWARE Battery Cyclers.

Setting Up DCIR Tests on NEWARE Battery Cyclers

NEWARE battery cyclers offer dedicated functions for DCIR testing through their advanced software capabilities. The system supports both step-based DCIR and pulse DCIR testing methods, making it ideal for research, development, and quality assurance applications.

Understanding NEWARE Cycler Series for DCIR Testing

NEWARE provides several battery cycler series designed for different testing requirements. Understanding which system suits your needs is essential for accurate internal resistance measurements.

The CT-4000 Series represents an excellent choice for laboratory-scale research with coin cells and small-format batteries. With current ranges from 50mA to 12A across triple-range configurations, these cyclers deliver exceptional measurement control. The triple-range design enables automatic switching between current ranges, providing optimal accuracy across the entire testing spectrum without manual intervention. This series features independent constant-current and constant-voltage sources for each channel, with data recording frequencies up to 10Hz and response times as fast as 1ms.

For testing laptop, tablet, and smartphone battery packs, the CT/CTE-5000 Series excels with its SMBUS/I2C communication capability for direct Battery Management System (BMS) integration. These cyclers achieve measurement accuracy reaching 0.02% full scale with response times under 10ms, capturing rapid transient behaviours critical for consumer electronics validation.

The CE-6000 Series provides robust solutions for testing high-power cells, modules, and complete battery packs in automotive and industrial applications. Supporting maximum voltages up to 3000V, this modular platform handles demanding requirements of electric vehicle battery development with regenerative energy technology and high-precision measurement capabilities.

For advanced simulation of real-world usage patterns, the CT/CTE-8000 Series delivers dynamic EV load simulation by replicating actual road-driving loads with dynamic current and power waveform simulation. These cyclers enable effortless implementation of complex drive cycle simulations with 10ms interval capabilities.

The CT-9000 Series represents NEWARE’s pinnacle achievement in battery testing technology, characterised by 1000Hz data recording frequency, four automatic-switch output ranges, 0.005% accuracy, and minimum 400µs pulse width capability. This makes it the preferred choice for cutting-edge electrochemical research and detecting minute differences in battery materials.

Precision Measurement Capabilities

Many NEWARE cyclers can achieve current accuracy up to ±0.02% full scale, depending on model and range selection, with 16-bit AD/DA resolution. This exceptional precision ensures that your DCIR measurements capture genuine battery characteristics without measurement errors interfering with results.

The true bipolar circuitry design enables seamless transitions between charge and discharge modes without switching delays or current spikes. This proves critical for DCIR testing where rapid current direction changes must occur smoothly for accurate readings.

Test Equipment Setup

NEWARE cyclers support multiple charging and discharging modes essential for DCIR testing:

Charging modes include constant current (CC), constant voltage (CV), constant current-constant voltage (CC-CV), and constant power (CP) charging.

Discharging modes include CC, CV, CC-CV, CP, and constant resistance (CR) discharging.

Pulse mode supports CC or CP charging and CC or CP discharging pulses with a minimum pulse width of 500 milliseconds. A single pulse step can include up to 32 distinct pulses.

Creating a DCIR Test Profile

To set up a DCIR test on NEWARE battery cyclers following the IEC standard, create the following test sequence:

Step 1: Rest the battery for 2 minutes to stabilise voltage readings.

Step 2: Charge the battery fully using CCCV (constant current and constant voltage) method.

Step 3: Rest the battery for another 2 minutes.

Step 4: Discharge at 0.2C for 10 seconds (records V₁ and I₁).

Step 5: Discharge at 1C for 1 second (records V₂ and I₂).

Step 6: Repeat steps 4 and 5 until the battery voltage drops below the cut-off voltage (often around 2.75 V for some lithium-ion cells; always follow the cell manufacturer’s specified cut-off voltage.).

You can download pre-configured test profiles or create custom profiles using the dedicated software interfaces that NEWARE systems provide.

Calculating Charge DCIR vs Discharge DCIR

NEWARE software uses specific data points to calculate both charge and discharge internal resistance:

Charge DCIR Calculation

For charge internal resistance: - Use the first second record (V₁, I₁) at the current charge step - Subtract the last second record (V₂, I₂) from the previous charge step - Take absolute values and apply the formula: R = |V₁ - V₂| / |I₁ - I₂|

Discharge DCIR Calculation

For discharge internal resistance: - Use the first second record (V₁, I₁) at the current discharge step - Subtract the last second record (V₂, I₂) from the previous discharge step - Calculate using the same formula: R = |V₁ - V₂| / |I₁ - I₂|

In battery research and applications, discharge internal resistance is generally considered more important than charge resistance because it directly affects how the battery delivers power during use.

Using NEWARE Software for DCIR Analysis

After completing your test, NEWARE software provides powerful tools for analysing DCIR data. The comprehensive software suite includes intuitive programming interfaces for creating complex test profiles with up to 65,535 cycles and 254 steps per program.

Accessing DCIR Calculator

The software includes dedicated DCIR calculation functions that allow you to choose between two calculation methods:

Step DCIR allows you to calculate resistance from standard charge/discharge step sequences. You can select “Calculate All Adjacent Steps” or configure specific step combinations.

Pulse DCIR is used when testing with pulse waveforms. This method follows the IEC standard procedure more precisely.

Configuring Step Combinations

In the DCIR settings, you can configure nine different step types for combination calculations:

• Constant Current (CC) Charge
• CC Discharge
• Constant Voltage (CV) Charge
• Rest
• CC-CV Charge
• Constant Power Discharge
• Constant Power Charge
• Constant Resistance Charge
• Constant Resistance Discharge

To create a valid combination, steps must be adjacent in your test sequence. For example, selecting CC Charge followed by CC Discharge creates a valid combination for DCIR calculation.

Generating Results

After configuring your settings, the software automatically calculates DCIR values and displays them in a data grid. You can:

• Copy data to Excel for further analysis
• Save graphs as JPG, PNG, or TIFF images
• Generate formatted reports
• Export data in CSV and JSON formats for compatibility with external analysis software

Real-time data visualisation helps you monitor test progress, whilst exportable formats streamline your workflow. The ability to display DCIR values in the main data window provides quick reference access during analysis.

Advanced Testing: HPPC and EIS Capabilities

NEWARE systems offer advanced testing capabilities beyond basic DCIR measurement that provide comprehensive battery analysis.

HPPC Testing for Dynamic Internal Resistance Analysis

HPPC (High Power Pulse Characterisation) testing provides a more comprehensive analysis of internal resistance under dynamic conditions. HPPC testing applies high power pulse currents to simulate real-world battery operation, such as acceleration and braking in electric vehicles. This method measures voltage response and internal resistance changes under stress.

The NEWARE systems comply with IEC standards for DCIR testing during HPPC procedures, allowing you to obtain dynamic DCIR values throughout the test.

Key parameters measured during HPPC testing include:

• DC Internal Resistance (DCIR) showing voltage drop under high power conditions
• Pulse power capability (maximum power output in specified time periods)
• Energy density measurements

HPPC test results help with battery design optimisation, cycle life prediction, and quality control for power battery applications.

Integrated Electrochemical Impedance Spectroscopy

The EIS Battery Cycler Series integrates Electrochemical Impedance Spectroscopy directly into the cycling platform, eliminating the need for separate testing stations. This integration enables automated switching between DC charge-discharge and AC impedance measurements without repeatedly mounting and unmounting batteries.

EIS functionality provides detailed battery state-of-health analysis, internal resistance profiling, and predictive diagnostics across frequency ranges that can extend from 10 mHz to 100 kHz. Impedance accuracy and channel counts depend on the model and configuration, and flexible test programming allows simultaneous impedance measurements during DC testing.

EIS measurements reveal critical information about ohmic resistance, solid electrolyte interphase (SEI) layer formation, charge-transfer kinetics, and lithium-ion diffusion processes. By integrating EIS directly into battery cyclers, NEWARE systems eliminate labour-intensive manual transfers between equipment, reduce measurement errors caused by varying electrical contacts, and enable continuous monitoring throughout charge-discharge cycling.

Factors Affecting Internal Resistance Measurements

Several factors influence DCIR measurements and must be controlled for accurate results:

State of Charge (SOC) significantly affects resistance. Batteries typically show higher resistance at very high or very low SOC levels, with the lowest resistance often occurring in mid-SOC ranges, depending on chemistry and test conditions.

Temperature has a major impact on resistance. Cold temperatures increase internal resistance because the electrolyte becomes more viscous, slowing ion movement. Testing should be conducted at controlled temperatures between 20-25°C for consistent results.

Current density affects measurements through polarisation effects. Higher currents intensify polarisation, potentially increasing measured DCIR values.

Battery age causes resistance to increase over time due to chemical degradation, SEI layer growth, and electrode deterioration.

Sampling time influences what components of resistance are captured. Shorter sampling times (around 10ms) primarily measure ohmic resistance, whilst longer times include polarisation effects.

Typical Internal Resistance Values

For reference, typical internal resistance values for different battery types are:

When internal resistance approaches or exceeds around twice the initial value, battery performance may be significantly degraded; confirm end-of-life criteria against your cell specification and application requirements.

Comparing DCIR and ACIR Testing Methods

Whilst this guide focuses on DCIR, understanding the difference between DCIR and ACIR (Alternating Current Internal Resistance) helps you choose the right test for your needs:

Both measurements are valid but reveal different aspects of battery resistance. DCIR provides values closer to actual operating conditions, making it preferred for evaluating power performance.

Practical Tips for Accurate DCIR Testing

For the best results when measuring internal resistance with NEWARE equipment:

Allow proper rest periods between charge and discharge steps to stabilise cell voltage before measurements.

Use appropriate current rates based on your battery specifications. The IEC standard uses 0.2C and 1C, but high-power cells may require different rates (5C-10C for some applications).

Maintain consistent temperature throughout testing. Temperature variations affect resistance readings significantly.

Record measurements at the same SOC when comparing batteries or tracking degradation over time.

Use four-wire connections where possible to eliminate errors from lead and contact resistance, especially for low-resistance measurements.

Verify equipment calibration regularly to ensure measurement accuracy, particularly when testing batteries with very low resistance values in the milliohm range.

Find recommended leads, fixtures, and low-resistance accessories here: Battery Testing Accessories.

Choosing the Right NEWARE System for Your Testing Needs

Selecting the optimal NEWARE battery cycler depends on several key factors including battery format, chemistry, voltage and current requirements, testing objectives, and throughput needs.

For laboratory research with coin cells and small-format batteries, the CT-4000 Series provides excellent precision and value. Consumer electronics manufacturers testing smart battery packs benefit from the CT/CTE-5000 Series’ BMS communication capabilities. Automotive applications requiring high-power testing demand the CE-6000 Series’ voltage and current capacity.

Research institutions pursuing cutting-edge electrochemical studies should consider the CT-9000 Series for its exceptional accuracy and transient measurement capabilities. Organisations requiring comprehensive battery diagnostics gain significant advantages from EIS-integrated models.

FAQs

Q1. What is DCIR testing and why is it important?

DCIR (Direct Current Internal Resistance) measures the battery's internal resistance by applying a current pulse and measuring the resulting voltage change. It indicates the battery's ability to deliver power and is a key degradation indicator. CT/CE-9000 complies with IEC standards for DCIR testing and provides dynamic DCIR values during cycling, helping identify capacity fade mechanisms.

Q2. How are Neware cyclers used in battery material research?

Researchers use CT/CE-9000 for detailed electrochemical analysis: dQ/dV differential capacity curves reveal degradation mechanisms, GITT measurements quantify diffusion coefficients, DCIR evolution tracks resistance growth, and 1000Hz data acquisition captures transient phenomena. These insights guide materials optimisation.

Q3. Can I analyze test results directly in Neware software?

Yes, the software provides curve plotting, capacity/cycle life graphs, DCIR calculation, dQ/dV generation, and statistical analysis. For complex analysis, exported data can be analyzed in MATLAB, Python, or specialized battery analysis software. Many researchers use the cycler's software for quick insights then perform detailed analysis externally.

Q4. What is the difference between DCIR measured by step methods and pulse methods?

Direct current internal resistance (DCIR) can be measured using either current-step or current-pulse methods, and each emphasises slightly different behaviour. In a step method, the current is changed from one steady value to another and the voltage response is recorded over a longer period. DCIR is then calculated from the quasi-steady voltage difference and current difference, making this approach well suited to characterising average polarisation under controlled conditions.

In a pulse method, short current pulses are applied and the immediate and short-term voltage changes are analysed. This is more sensitive to fast dynamic behaviour relevant to power delivery and transient loads. In practice, many laboratories use step methods for fundamental characterisation and pulse methods for application-focused testing and model validation.

Q5. How does test temperature control influence DCIR repeatability and inter-lab comparability?

Internal resistance is strongly temperature-dependent. Even small temperature differences can cause noticeable changes in DCIR, because electrolyte conductivity, reaction kinetics and diffusion processes all vary with temperature. If cell temperature is not tightly controlled and allowed to reach thermal equilibrium before each measurement, repeated DCIR tests on the same cell may give different results.

For inter-lab comparisons, consistent temperature set-points, soak times and measurement sequences are essential. Ideally, both the environment (chamber or room) and the cell surface or core temperature are monitored and recorded. When temperature control is rigorous and well documented, DCIR data become far more repeatable, traceable and suitable for comparing different laboratories, chemistries or test programmes.

Q6. When should I use EIS instead of (or alongside) DCIR for state-of-health studies?

DCIR provides a single resistance value under a given operating condition. It is simple, fast and well suited to quality control, production testing and BMS algorithms that require a compact health indicator. However, DCIR cannot by itself distinguish between ohmic, charge-transfer and diffusion contributions.

Electrochemical impedance spectroscopy (EIS) resolves the cell response over a range of frequencies and can separate different processes such as contact resistance, SEI growth, charge-transfer resistance and mass transport limitations. EIS is therefore more informative for mechanism-level ageing studies, model development and root-cause analysis.

In many programmes, DCIR is used routinely to track state of health over many cycles, while EIS is applied periodically or to selected samples to understand why DCIR and capacity are changing, and to calibrate or refine equivalent-circuit models.

Q7. How do I minimise lead and contact resistance when measuring low-milliohm cells?

To obtain reliable DCIR values for low-resistance cells, the test setup must minimise and stabilise all additional resistances. Use four-wire (Kelvin) connections, with separate current-carrying and voltage-sensing leads placed as close as practical to the cell terminals. Keep cables short, well-organised and mechanically supported to avoid movement during the test.

Contact areas should be clean, flat and free from oxide or contamination. Spring-loaded fixtures, busbars or appropriately torqued bolts can help maintain consistent contact pressure. Where possible, characterise the fixture resistance using a shorting bar or a precision shunt, and apply any correction procedures supported by your cycler software. Consistency in fixturing is just as important as low absolute resistance; changing clamps or tightening force between tests can introduce unwanted scatter in DCIR data.

Q8. What DCIR trends typically indicate ageing or safety risk during cycling?

Over time, most cells show a gradual increase in DCIR as SEI layers thicken, active material is lost and contact interfaces degrade. A smooth, progressive rise in DCIR alongside capacity fade is a normal ageing signature and can often be managed through updated operating limits.

Warning signs include sudden jumps in DCIR, strong divergence between cells in the same pack, or rapid DCIR growth at specific states of charge or temperatures. These behaviours may indicate internal damage, gas generation, loss of electrolyte or lithium plating. When DCIR changes become pronounced, cells may heat more during load, deliver less power and move closer to manufacturer-defined safety limits.

Many standards and manufacturers treat a substantial increase in DCIR as part of an end-of-life criterion, but the exact thresholds should always follow the cell specification, safety guidelines and application requirements rather than a single universal rule.

Conclusion

Measuring charge and discharge internal resistance with NEWARE battery cyclers provides essential insights into battery quality, performance, and health. By following the IEC 61960 standard method and using NEWARE’s dedicated DCIR calculation tools, you can obtain accurate, reproducible results for research, development, and quality control applications.

The key formula to remember is DCIR = (V₁ - V₂) / (I₂ - I₁), using voltage and current readings from two discharge steps. With proper test setup, controlled conditions, and understanding of the factors affecting internal resistance, you can effectively evaluate any battery’s performance characteristics and make informed decisions about battery selection, design, and lifecycle management.

NEWARE battery cyclers deliver the precision, reliability, and versatility required for rigorous battery analysis. Whether evaluating next-generation solid-state batteries, optimising lithium-ion formulations, or validating EV battery pack performance, NEWARE cyclers provide the trusted foundation for internal resistance testing and comprehensive battery development.

Ready to get started with NEWARE battery testing? Contact our expert team to discuss your specific battery testing requirements and find the ideal system for your laboratory, research centre, or manufacturing facility.