How To Select Film Capacitors For Charging Stations: A Selection Guide Based On Market Research And Technical Specifications

 

I. Industry Background: The Boom in the Charging Station Market Drives Demand for Core Components
In 2026, China's charging station industry is experiencing a period of synergy between policy-driven growth and technological innovation. According to data from the China Electric Vehicle Charging Infrastructure Promotion Alliance, by the end of 2025, the national inventory of charging infrastructure had surpassed 20 million units, reaching 20.092 million, with the vehicle-to-charger ratio optimized to 2.2:1. The "Three-Year Doubling Action Plan for Electric Vehicle Charging Facility Service Capacity (2025–2027)," jointly issued by the National Development and Reform Commission and multiple government departments, explicitly requires the construction of 28 million charging facilities nationwide by the end of 2027, providing over 300 million kilowatts of public charging capacity.

The rapid expansion of the charging station market has directly driven demand for upstream core components-thin-film capacitors. According to data from the China Research and Consulting Institute, the market size for thin-film capacitors in China's electric vehicle sector is projected to reach 6.98 billion yuan in 2025, representing a year-on-year growth of 57.1%. This growth rate is significantly higher than the average growth rate of approximately 18.3% for the overall domestic automotive electronics market during the same period. Among these, DC-Link thin-film capacitors-as key components in charging station power modules that provide voltage support and ripple suppression-have become a top priority in product selection and design.

II. The Role of Film Capacitors in Charging Stations
In the power electronics systems of charging stations, film capacitors primarily serve the following three functions:

1. DC-Link Support (DC-Link Capacitors)

Smooth and filter the rectifier output voltage to provide a stable DC voltage
Absorb high-amplitude ripple currents drawn by the inverter from the DC bus, preventing them from generating high-amplitude ripple voltages across the bus impedance
Prevent bus voltage overshoot and transient overvoltages from damaging power devices such as IGBTs
2. Electromagnetic Interference Suppression (EMI/X-Y Safety Capacitors)

Suppresses electromagnetic interference (EMI) conducted through power cables to meet electromagnetic compatibility (EMC) standards
Provides safety isolation to ensure personal safety
3. Snubber Capacitors

Absorbs the voltage spikes generated when power switching devices turn off
Reduces switching losses and protects power devices
In the above applications, DC-link capacitors-due to their high capacitance and significant cost-are a key consideration in the selection of film capacitors for charging stations.

 

III. Selecting Dielectric Materials for Film Capacitors: Why Polypropylene Film Is the Top Choice for Charging Stations
The core characteristics of film capacitors depend largely on their dielectric materials. Currently, the two mainstream dielectric materials are polypropylene (PP) and polyester (PET). In charging station applications, metallized polypropylene film capacitors (MKP type) dominate the market.

Key Advantages of Polypropylene Film Capacitors (MKP/PP):

Extremely low tangent delta (tan δ), making them one of the lowest-loss types among all film capacitors; excellent high-frequency performance; high current-carrying capacity; and minimal temperature rise
Excellent temperature and frequency stability, with minimal variation in capacitance values with temperature and frequency
Excellent self-healing capability-when microscopic defects in the film dielectric cause localized breakdown, the metal layers surrounding the breakdown point evaporate to isolate the fault, restoring capacitance functionality
Outstanding insulation resistance and extremely low leakage current
Non-polar, compatible with both AC and DC, and capable of withstanding reverse voltage

 

Limitations of polyester film capacitors (MKT/PET):

They have a relatively high tangent delta, resulting in significant losses and temperature rise in high-frequency or high-current applications.
Their capacitance varies considerably with temperature and frequency, and they are less stable than polypropylene capacitors.
Therefore, in high-voltage, high-current applications with a wide temperature range-such as charging stations-metallized polypropylene film capacitors are the optimal choice in engineering practice.

IV. Detailed Explanation of Key Selection Parameters
4.1 Rated Voltage (Vr)
Select a voltage rating that is at least 1.5 to 2 times the circuit's operating voltage to ensure a safety margin. The mainstream bus voltage levels for current charging stations range from 750 VDC to 1000 VDC. Taking a 120 kW fast-charging station as an example, its DC bus is typically configured with film capacitors rated at 630 VDC to 1100 VDC. The typical rated voltage range for DC-Link film capacitors is 600 VDC to 3600 VDC.
 

4.2 Capacitance (C)
The selection of capacitance must satisfy both energy storage buffering and ripple filtering requirements:

Energy storage buffering: C ≥ 2 × P × t / ΔV², where P is the rated power (W), t is the allowable duration of power fluctuations (s), and ΔV is the allowable amplitude of voltage fluctuations (V)
Ripple filtering: C ≥ I_ripple / (2π × f × ΔU), where the switching ripple frequency of the PFC/inverter (typically 10 to 100 kHz) must be verified
Industry experience indicates that the DC bus of a 120 kW fast-charging station is typically configured with 3 to 6 10,000 µF/630 V screw-type capacitors connected in parallel, with the exact number determined by the ripple current rating. The typical capacitance range for DC-Link film capacitors is 100 µF to 7,200 µF (per unit).

4.3 Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL)
Thin-film capacitors offer significant advantages over aluminum electrolytic capacitors in terms of ESR and ESL: ESR is as low as the milliohm range, with a minimum of 0.2 to 0.5 mΩ; ESL is extremely low, meeting the low-inductance design requirements of inverters. Low ESR and low ESL directly impact the efficiency and thermal management design of charging station power modules.

4.4 Peak Current and dV/dt
The peak current capability of a film capacitor is determined by the following formula:

I (A) = C (µF) × dV/dt (V/µs)

The dV/dt value and the pulse characteristic parameter K0 are provided in each product datasheet. For continuous pulse conditions, thermal evaluation must also be performed in accordance with thermal analysis requirements.

4.5 Operating Temperature Range and Service Life
Outdoor charging stations are exposed to harsh environmental conditions:

Operating temperature range: Typically required to be -40°C to +85°C (outdoor environment); some high-end products require -55°C to +105°C
Actual internal cabinet temperatures in summer can reach 65°C to 75°C
Film capacitors have an expected service life of up to 100,000 hours, with some products achieving a service life of up to 200,000 hours (under +105°C conditions)
Based on industry experience, selecting specifications rated for 105°C with a lifespan of ≥50,000 hours, and applying the "10-degree rule" to a 65°C operating environment, results in a calculated lifespan of approximately 20,000 hours (about 10 years), which meets the design lifespan requirement of ≥10 years for charging stations.

4.6 Self-healing Properties
Self-healing is one of the core advantages of metallized film capacitors. When microscopic defects in the film dielectric cause localized breakdown, the metal coating surrounding the breakdown point instantly vaporizes, thereby isolating the fault and restoring capacitive function (with only a slight decrease in capacitance). The quality of the film dielectric, the quality of the metallized coating, the capacitor design, and the manufacturing process collectively determine the effectiveness of the self-healing capability.

 

 

 

V. Film Capacitors vs. Aluminum Electrolytic Capacitors: A Comparison of Technical Approaches
Currently, there are two primary technical approaches for DC-link capacitors: film capacitors and aluminum electrolytic capacitors. With advancements in metallization and coating technologies, as well as film capacitor technology, the use of film capacitors in DC-link applications has become an industry trend.

Comparison Criteria	Metallized Polypropylene Film Capacitors	Aluminum electrolytic capacitors
Polarity	Non-polar; can withstand reverse voltage	Polarized; reverse connection will cause damage
ESR	Extremely low (0.2–0.5 mΩ)	Relatively high
Ripple Current Handling Capability	High	Limited by heat generated by ESR
Self-healing Capability	Self-healing capability	No self-healing capability
Lifespan	Up to 100,000 hours or more	Highly temperature-sensitive; relatively short lifespan
Temperature Characteristics	Excellent; minimal capacitance drift	Temperature-sensitive; capacitance decreases at low temperatures
Dielectric Strength	Up to 3,600 VDC	Typically low
Dimensions	Larger size for the same capacitance	Compact size

In charging station applications, film capacitors are rapidly replacing aluminum electrolytic capacitors due to their comprehensive advantages, including long service life, high reliability, and low loss; they have become the mainstream choice, particularly in high-power fast-charging and ultra-fast-charging scenarios.

 

 

VI. Key Certifications and Standards
Film capacitors used in charging stations must comply with a series of industry standards and certification requirements:

GB/T 17702: General Specifications for Power Electronics Capacitors
NB/T 11388-2023: Technical Specifications for DC Support Capacitors
IEC 61071: Standard for Capacitors for Power Electronics
AEC-Q200: Automotive-Grade Passive Component Certification (Applicable to On-Board Charger (OBC) applications)
UL 94 V-0: Flame Retardant Rating Requirements for Enclosures
GB 39752-2024 "Safety Requirements for Electric Vehicle Power Supply Equipment" (Effective August 1, 2025)
GB 44263-2024 "Safety Requirements for Electric Vehicle Conductive Charging Systems" (Effective August 1, 2025)
For On-Board Charger (OBC) applications, special attention must be paid to AEC-Q200 certification, which sets clear reliability requirements for harsh operating conditions such as high temperatures (125°C), high humidity, and vibration.

 

VII. Market Landscape and Major Suppliers
Global Market Overview
According to QYResearch data, the global market for capacitor films used in new energy vehicles is projected to reach $283 million in 2025 and is expected to exceed $585 million by 2032, with a compound annual growth rate (CAGR) of 11.0% from 2026 to 2032. As the world's largest market, China is expected to account for 45% of global production capacity in 2025.

 

VIII. Selection Process and Practical Recommendations
Systematic Selection Steps
1. Determine Electrical Parameters

Identify the busbar rated voltage and peak voltage, and select a voltage withstand rating of ≥1.5 times the operating voltage
Calculate the required capacitance based on the power rating and ripple requirements
Verify the RMS value of the ripple current to ensure it does not exceed the capacitor's rated ripple current
2. Evaluate Environmental Conditions

Determine the operating temperature range (outdoor charging stations require special attention to high-temperature and high-humidity environments)
Evaluate the impact of altitude on voltage withstand derating
Consider special environmental factors such as salt fog and corrosive gases
3. Mechanical Structure Compatibility

Select an installation method, such as bolt-on, PCB-mounted, or stacked busbar
Verify that the dimensions match the cabinet space
Assess thermal design requirements
4. Certification and Reliability Validation

Confirm that the product has passed the required industry standard certifications
Request third-party test reports from the supplier
Conduct in-system testing and validation of samples

Common Selection Mistakes
Focusing solely on capacitance and voltage rating while ignoring ESR and ESL parameters
Failing to account for voltage derating in high-temperature environments
Underestimating the impact of ripple current on capacitor temperature rise
Failing to perform thermal analysis for continuous pulsed operating conditions
Ignoring the requirements for moisture resistance and corrosion protection in outdoor environments

 

IX. Technological Trends
High-Temperature Resistance Technology: With the widespread adoption of silicon carbide (SiC) power devices, inverter operating temperatures have risen, placing higher demands on the temperature resistance of film capacitors. High-temperature-resistant modified polypropylene film and products rated for 125°C are becoming the mainstream.

Miniaturization and High Capacitance: Through improvements in metallization processes and multilayer structure design, film capacitors are evolving toward smaller sizes and higher capacitance density.

Integration with Bus Bars: Integrating DC-link capacitors with bus bars can further reduce loop parasitic inductance and improve system efficiency.

Intelligent Monitoring: Some high-end products are beginning to integrate temperature and voltage monitoring functions to enable real-time monitoring of the capacitor's health status.

 

X. Conclusion
Selecting film capacitors for charging stations is a systematic process that requires comprehensive consideration of multiple factors, including electrical parameters, environmental adaptability, mechanical structure, certification compliance, and cost control. Metallized polypropylene film capacitors have become the mainstream technology for DC-Link applications in charging stations due to their low loss, high reliability, long service life, and self-healing properties.

As the construction of charging stations enters a critical phase in 2026 and new technologies such as silicon carbide accelerate their penetration, the film capacitor industry is poised for a new round of technological upgrades and market expansion. It is recommended that procurement engineers and R&D personnel base their selection on systematic parameter matching and validation under actual operating conditions, making informed decisions after thoroughly evaluating suppliers' technical capabilities and product certification systems.