Problem Type: High-Temperature Lifespan Bottleneck
Q: How can we ensure that the lifespan of key filtering components in OBC modules operating under the harsh 85°C core temperature environment commonly faced in automotive electronics truly matches the lifespan of the vehicle?
A: High-temperature lifespan is a system-level challenge that requires comprehensive evaluation, not just for individual components.
After selection confirmation, the capacitor core temperature (not surface temperature) must be measured during the prototype stage to ensure it does not exceed the limit. It is recommended to establish a supplier lifespan data traceability mechanism.
Problem Type: PCB and Structural Layout Adaptation
Q: What are the main challenges encountered when using film capacitors in PCB and structural layout?
A: Layout challenges need to be included in the review during the conceptual design stage to avoid high costs for later modifications. The main challenges are heat dissipation, space, and mechanical stress.
The Conflict Between Heat Dissipation and Space: Capacitors require ventilation and heat dissipation, but compact layouts limit space, requiring precise balancing through thermal simulation.
Mechanical Stress: The uneven expansion of the leads of pin-type capacitors and the PCB during temperature changes can easily lead to fatigue cracking of the solder joints.
Vibration Risk: Vehicle vibration may loosen large capacitors, making soldering alone unreliable.
Solutions: Optimize the layout using thermal simulation, incorporate stress-relief holes in the PCB design, and add mechanical fixation such as clamps or adhesives for large capacitors. In addition to the above countermeasures, it is recommended to use a thermal imager to conduct actual thermal distribution measurements on the prototype and verify the simulation. For pin-type capacitors, temperature cycling (-40°C to 125°C) solder joint reliability testing is mandatory.
Problem Type: Long Lifespan Design of OBC Capacitors
Q: The customer requires that the OBC capacitors do not need to be replaced during the entire vehicle lifespan (15 years / 300,000 km). How can this requirement be met through design, selection, and testing?
A: The customer’s “no replacement” requirement is a hard requirement and must be addressed from the design stage and written into the technical agreement. Selection: Select metallized polypropylene film capacitors with a lifespan ≥100,000 hours (approximately 11.5 years) at 85°C and exceeding 15 years under low-temperature conditions, covering the entire vehicle lifecycle;
Design Redundancy: Reserve ≥30% capacity and ripple current margin, control capacitor temperature rise ≤15°C, reduce working stress, and delay degradation;
Testing and Verification: Accelerate aging at 125°C/1000 hours, and calculate actual lifespan using the lifespan-temperature curve; conduct environmental tests including high and low temperature cycling, damp heat, and vibration to ensure stable performance.
The testing and verification process should include “actual operating condition simulation aging test,” applying a target ripple current at 85°C for >3000 hours of testing, using data to support the results. The margin design must be reflected in circuit simulation.
Problem Type: High-Frequency Filtering Challenge
Q: In the OBC PFC circuit, as the switching frequency increases, how can we ensure that the DC-Link capacitor can still effectively suppress high-frequency ripple and prevent drastic bus voltage fluctuations that could trigger the system protection circuit to interrupt charging?
A: High-frequency filter failure is a systemic problem that needs to be addressed from three dimensions: capacitor design, layout, and control.
Prioritize obtaining impedance curves for capacitors above 100kHz. On the PCB, the input and output loop area of the capacitor must be minimized; multilayer busbars should be used if necessary.
Problem Type:800V Platform Withstand Voltage
Q: For the 800V high-voltage platform in new energy vehicles, how can the long-term reliability of the capacitor’s withstand voltage be guaranteed when subjected to high-voltage, high-ripple current surges to avoid failure due to insufficient withstand voltage?
A: 800V withstand voltage reliability must be guaranteed by a triple approach: design margin + process control + test coverage.
When selecting capacitors, a rated voltage of 1000V or higher is recommended. Production batches should be sampled and subjected to high-voltage steady-state load testing (e.g., 1.2 times the rated voltage, 85°C, 96 hours).
Problem Type: Cost and Performance
Q: How to balance the cost and performance of film capacitors in the design?
A: Balancing cost and performance is crucial for project success, requiring a clear cost model and performance baseline.
Implement a “tiered selection” strategy: Use high-performance film capacitors for Tier A (critical path); use hybrid or optimized electrolytic capacitors for Tier B (non-critical). Negotiate annual price reduction plans with suppliers.
Problem Type: PFC Circuit Failure
Q: How exactly does the failure of the DC-Link capacitor in the PFC circuit of the OBC module (capacitance degradation, increased ESR) trigger the system protection mechanism and interrupt charging?
A: A deep understanding of how the failure propagates to the system level is needed to set effective early warnings. It is recommended to add a ripple voltage detection circuit in the hardware and set an early warning threshold based on the effective value of the ripple in the software, earlier than the hardware protection action, providing users with a buffer time.
Problem Type: Replacement Cost Considerations
Q: Compared to mature and lower-cost electrolytic capacitors, how can we reasonably assess and accept the initial bill of materials (BOM) cost premium of high-performance film capacitors in the OBC under the drive of high reliability requirements?
A: The BOM cost premium needs to be explained internally and to customers using “value engineering,” rather than simply comparing unit prices. Create a clear TCO analysis template to quantify potential after-sales costs and brand reputation loss. For high-end models, “long-life capacitors” are marketed as a product highlight.
Problem Type: Failure Mode Avoidance
Q: How can we design to avoid frequent after-sales failures in the OBC due to capacitor issues?
A: Avoiding after-sales failures is one of the core design goals, requiring a systematic checklist of preventative measures.
In DFMEA, the Risk Priority Number (RPN) of electrolytic capacitor-related failure modes is set as a mandatory improvement item, forcing the adoption of solid-state solutions such as film capacitors. A quality profile for key component suppliers is established.
Problem Type: Miniaturization and Performance Balance
Q: New energy vehicles are pursuing miniaturization. How can sufficient performance and lifespan be guaranteed when capacitors in the OBC become smaller?
A: Miniaturization and long lifespan are a contradictory yet unified concept, testing system integration and material innovation capabilities. Custom sizes are developed in collaboration with capacitor suppliers. Structurally, the capacitor mounting surface is directly in contact with the heat sink, achieving “integrated structural heat dissipation” to offset the temperature rise caused by the reduced size.
Problem Type: Charging Performance Degradation
Q: My car uses an 800V high-voltage platform. Why does the charging speed seem to slow down after a few years of use, and sometimes it doesn’t even fully charge?
A: Slower charging is a common problem. First, external factors such as charging station power and battery capacity should be ruled out. This problem is very likely due to a key component inside the on-board charger (OBC)—the capacitor. It’s recommended to make it a habit to request the after-sales service to read the OBC data during annual maintenance and check for any “capacitor performance warning” logs. Choosing a model that supports battery health management and OBC status monitoring is more convenient.
Problem Type: Capacitor Physical Failure
Q: The after-sales service said my OBC module is faulty. Upon disassembly, they found a bulging capacitor inside. What caused this?
A: A bulging capacitor is a typical physical phenomenon of traditional electrolytic capacitor failure. The root cause is that when the OBC operates at high temperature and high frequency for a long time, the electrolyte inside the capacitor generates gas due to heat, leading to increased internal pressure, which eventually deforms the outer casing. Seeing a bulging capacitor is a major concern for users regarding safety and repair availability. If bulging is detected, immediately stop using the OBC for charging and switch to slow charging or take the vehicle to a repair shop, as the bulging capacitor may fail completely at any time, causing more serious malfunctions.
Problem Type: High Voltage Withstand Voltage Protection
Q: I heard that the 800V platform has higher requirements for components. How do the capacitors in the OBC avoid being damaged by excessive voltage?
A: “High voltage breakdown” is a safety concern and requires a clear explanation and reassurance. Check the vehicle’s specifications or ask the salesperson if the OBC indicates the use of “film capacitors” or “reinforced insulation design.” These types of vehicles have better high voltage safety.
Problem Typee: High Temperature Environment Adaptability
Q: Will the heat generated by the OBC during operation affect its lifespan? How do capacitors cope with high temperatures?
A: Car owners are concerned about the “hidden damage” of high temperatures to vehicle components. In summer, avoid high-power fast charging immediately after the vehicle has been exposed to direct sunlight; allow the vehicle to cool down for a while. This significantly reduces the internal starting temperature of the OBC, which is beneficial for any capacitor.
Problem Type: Charging System Aging
Q: Are vehicles with 800V fast charging platforms more prone to charging system aging issues?
A: The misconception that “new technology = more delicate” needs to be corrected.
Pay attention to clauses in automakers’ advertising regarding “lifetime warranty on core components” or “long-life design,” as these are often directly related to the use of high-performance components such as film capacitors.
Problem Type: High-Frequency Operating Condition Adaptation
Q: To pursue charging efficiency, the OBC operates at a very high frequency. Will this affect the capacitor?
A: High-frequency operation is a “silent burden” for car owners and needs to be linked to a perceptible experience. When using the same fast charging station, if the vehicle’s charging efficiency (kW) is significantly lower than other similar models, or if the OBC area is abnormally hot, it may be a sign of poor high-frequency capacitor performance.
Problem Type: System and Reliability
Q: Can simply replacing a capacitor really improve the overall reliability of the vehicle so much?
A: The logic of “small parts, big impact” needs a vivid analogy. The capacitor is like the “voltage regulator” and “firefighter” of the charging system. A reliable, long-lasting “firefighter” can prevent the entire “workshop” (OBC) from needing major repairs due to minor sparks (voltage fluctuations).
Problem Type: Intermittent Fault Troubleshooting
Q: My 800V platform vehicle occasionally displays “Charging System Fault” on the dashboard during fast charging, but it charges normally again after restarting the vehicle. What could be causing this intermittent problem?
A: This intermittent fault is most likely caused by the unstable high-temperature performance of the capacitors in the OBC. During continuous high-current fast charging, the internal temperature of the OBC rises sharply. The ESR of traditional electrolytic capacitors changes drastically with temperature, causing the DC-Link voltage to fluctuate instantaneously beyond the threshold, triggering system protection. Intermittent faults are the most frustrating for car owners and are difficult to reproduce with after-sales service. It is recommended that car owners take photos of the dashboard, the charging pile screen displaying power, and the ambient temperature when the fault message appears. This information can greatly help after-sales engineers quickly pinpoint whether the problem is due to high capacitor temperature.
Problem Type: Low Temperature Environment Adaptation
Q: Why is the OBC failure rate of the same 800V model significantly higher in colder regions than in warmer regions?
A: This reveals the temperature adaptability defects of traditional electrolytic capacitors. In cold environments, electrolyte viscosity increases and conductivity decreases, leading to a sharp increase in capacitor ESR. Simultaneously, frequent hot and cold cycles accelerate electrolyte evaporation and material aging. Regional differences in failure rates are a significant factor influencing owner feedback. For owners in northern regions, it is recommended to charge in underground garages or indoors during winter and preheat the battery and vehicle via the app before traveling; this is beneficial for protecting all high-voltage components, including the OBC.
Problem Type: Repair Cost Control
Q: We have found that the OBC repair cost of 800V models is much higher than that of 400V models. Which components are the main contributors to the higher cost? How can it be reduced?
A: The core reason for the high OBC repair cost on the 800V platform is the cascading damage to high-voltage components. When a critical filter capacitor fails, it generates severe voltage and current fluctuations, damaging expensive power switching devices (such as SiC MOSFETs). You can proactively ask “whether the damage is caused by a capacitor problem” and find out if the replaced capacitor is a long-life model to avoid failure again in the short term, which will save you money in the long run.
Post time: Dec-16-2025