In drone/model aircraft propulsion systems, the electrolytic capacitor at the input of the ESC power board, installed at the power input and in front of the power MOSFET, plays a crucial role in absorbing peak current from the battery and stabilizing the bus voltage. For high-performance racing drones, industrial drones, and racing drones, this location is a critical node in the instantaneous high-current transmission path, directly affecting the stability of the ESC operation.

When a drone performs extreme maneuvers such as rapid acceleration, high-speed right-angle turns, and steep climbs, the ESC needs to output extremely large instantaneous currents to the motors within milliseconds. At this time, the input electrolytic capacitor not only has to perform conventional filtering and energy storage functions but also withstands extremely high instantaneous current loads, becoming one of the core components determining the reliability of the ESC under extreme operating conditions.

Why do capacitors fail at the input of drone ESCs?

In practical applications, typical failure scenarios reported by customers are: high-performance racing drones and racing drones often experience sudden ESC stalling and drone crashes during competitions or high-intensity flights, especially when performing rapid acceleration and high-speed right-angle turns. Disassembly revealed that the failure points were highly concentrated on the external solder joints of the electrolytic capacitors at the ESC input terminal, or at the connection points between the capacitor's internal leads and the foil. Specifically, the solder joints melted, and the internal leads overheated and broke, leading to irreversible damage to the ESC hardware. This not only resulted in the competition loss but also posed a safety hazard.

It is worth noting that the core cause of this type of failure is not limited to conventional electrical performance parameters. The customer had previously tried using liquid aluminum electrolytic capacitors with nominal ESR (Equivalent Series Resistance) and ripple current meeting standards, and even tested more expensive solid-state capacitors. However, under high-load maneuvering scenarios, these capacitors still could not meet the instantaneous high current handling requirements of the UAV ESC, and the failure problem remained unresolved.

Root Cause: More Than Just ESR and Ripple Current

Under the impact of extreme instantaneous currents, the physical path of current transmission becomes a performance bottleneck: if the cross-sectional area of ​​the capacitor's internal leads and external wires is insufficient, it will cause a sudden increase in local current density, generating a large amount of heat; if the lead material is of insufficient purity, has excessively high resistance, or the solder joint impedance is too high and mechanical strength is insufficient, these connection points will become weak points in the entire circuit under the combined effects of thermal stress and electromagnetic forces, ultimately leading to melting or breakage failure.

Therefore, for high instantaneous current scenarios such as the input of drone ESCs, capacitor selection should not be limited to the conventional criteria of "low ESR" and "ripple current compliance." It is crucial to focus on the capacitor's current-carrying structure design, internal connection process, and structural reliability under high-pulse conditions, mitigating the failure risk caused by instantaneous high currents from a physical structural perspective.

Yongming's Application Solution for Through-hole Aluminum Electrolytic Capacitors

Addressing the pain point of instantaneous high currents under high-load maneuvering of drone ESCs, Yongming has specifically launched the LKF/LKM series of through-hole aluminum electrolytic capacitors as a dedicated solution for this scenario. This series of capacitors not only boasts a low ESR advantage, with measured ESR as low as below 20mΩ, comparable to leading Japanese brands, but also employs a special lead structure design, enabling a single capacitor to handle a ripple current of up to 5500mA, stably handling the instantaneous ultra-high current demands of drone ESCs. The product is optimized in both electrical performance and physical structural reliability to ensure no structural failure under extreme flight conditions, guaranteeing stable ESC operation.

To further enhance instantaneous current carrying capacity and thermal shock resistance, we have specifically reinforced the capacitor's key current transmission paths; we utilize low-impedance, high-reliability internal connection technology to minimize hotspot temperature rise during current transmission; and combined with overall thermal design and a high-quality material system, we effectively reduce localized heat accumulation under high current surges, fundamentally solving the problem of pin and lead burnout due to overheating.

This solution differs from the selection logic of conventional general-purpose capacitors—conventional selection only focuses on basic electrical performance parameters and is suitable for ordinary filtering and energy storage scenarios; while the Yongming LKF/LKM series is specifically designed for applications involving high-frequency pulsed high current and frequent high-load maneuvers, better meeting the actual operational needs of UAV ESCs.

Application Testing Feedback
We compared the actual operational effects before and after replacing the capacitors with Yongming LKF series capacitors under the same or even more stringent extreme flight test conditions (such as continuous "full throttle-sudden braking" cycles):

Before adjustment (using conventional capacitors): The highest temperature of the capacitor leads reached 237℃, and frequent pin or internal conductor burnout occurred during the test, making it impossible to complete a full test cycle.

After adjustment (using Yongming LKF series): The highest temperature of the capacitor leads dropped to 117℃, a significant decrease of 120℃ in temperature rise, and no further pin or conductor burnout occurred throughout the entire test cycle, indicating stable operation.

Test results show that Yongming LKF/LKM series capacitors significantly reduce the temperature rise of leads under instantaneous high-current surges, completely eliminating physical connection failures caused by overheating. This fully verifies their structural reliability under extreme pulse conditions and makes them perfectly suited to the high-load operation requirements of drone ESCs.

Scenario-Based Q&A

Q1: When a drone accelerates rapidly or makes quick turns, the capacitor leads on the ESC always burn out. I've tried low-ESR capacitors on the market, but the problem persists. What could be the reason?

A: Based on industry application experience, the root cause of this problem is not solely ESR or ripple current; the core issue lies in the physical current-carrying structure design of the capacitor. Under extreme instantaneous current, insufficient lead or internal pin cross-sectional area of ​​conventional capacitors, or excessively high impedance at connection points, can lead to a rapid increase in local temperature, resulting in melting. For this type of scenario, capacitor selection must consider both high-current-resistance structural design and internal connection reliability to fundamentally solve the problem.

Q2: When purchasing capacitors specifically for drone ESCs, besides ripple current and ESR, what other key points should be considered? A: Based on our experience with this solution, three key points require additional attention: First, does it possess a specialized structural design for high-current scenarios? Second, does it employ low-impedance, high-reliability internal connection technology? Third, does it reduce the risk of localized overheating through material optimization and overall thermal design? For applications involving high instantaneous peak currents, such as drones, power tools, and car starters, these factors directly determine the structural reliability and lifespan of the capacitor.

Conclusion

For the input of drone ESCs, electrolytic capacitors not only perform basic functions of input filtering and energy storage but are also critical load-bearing components in the instantaneous high-current transmission path of the battery. When applications involve high-load maneuvers such as rapid acceleration, high-speed turning, and steep climbs, the main failure modes of capacitors are concentrated in the melting of pin solder joints and the overheating and breakage of internal leads, directly affecting drone flight safety and equipment reliability.

Addressing this industry pain point, YMIN's LKF/LKM series plug-in aluminum electrolytic capacitors provide a dedicated application solution, precisely matching the core requirements of drone ESCs for high instantaneous current carrying capacity and structural reliability, ensuring the stable operation of the drone's power system. For further information on relevant model specifications and samples, or to request targeted application selection technical support, please contact us for further matching based on your specific voltage, capacity, and size requirements.

【Abstract】
"Applicable Scenarios": "Drone/model aircraft power systems, ESC power board input terminals, high-load maneuvering instantaneous high-current scenarios",

"Core Advantages": "High-current resistant structural design, low internal resistance, eliminates pin/lead fuse failure",

"Recommended Models": "LKF 35V 1200μF 10×30; LKM 63V 1200μF 12.5×30; LKM 100V 1000μF 18×31.5; LKM 80V 680μF 12.5*30",

"Action Guidelines": "Obtain specifications, obtain samples, and receive technical support"