Supercapacitor Bank 2.7V 500F: Real Capacity Testing & Applications

ESR (Equivalent Series Resistance) is the inherent resistive property within every capacitor, varying by type (electrolytic, tantalum, ceramic). In high current applications, ESR causes significant problems. Using a 4700μF electrolytic capacitor at 25V with 5A output current dissipates 3W, causing a 60°C temperature rise. Heat dries the internal chemical compound, increasing ESR in a snowball effect that leads to failure. The solution is to use multiple capacitors in parallel, distributing power dissipation and reducing temperature rise in each component.

ESR (Equivalent Series Resistance) is the inherent resistance component in electrolytic capacitors that causes power loss and heat generation when current flows through it, following the formula P = I² × ESR; this heating can cause electrolyte evaporation, increased ESR, accelerated aging, and eventual failure, making low-ESR capacitors or parallel connections essential for reliable power supply design.

ESR (Equivalent Series Resistance) is the total parasitic resistance inherent in real capacitors, including lead resistance, dielectric resistance, and electrode resistance. Unlike ideal capacitors that only store charge, real capacitors behave as a combination of capacitance in parallel with resistance. High ESR causes capacitor heating, reduced filtering effectiveness, and can lead to bulging or explosion. The formula for capacitor reactance shows that higher frequencies result in lower opposition to current flow, making ESR particularly critical in switching power supplies and high-frequency circuits.

The Equivalent Series Resistance (ESR) is a parasitic parameter that causes capacitor heating through power dissipation (P = I² × ESR). Higher currents result in more significant heating. For electrolytic capacitors, ESR is inversely proportional to voltage rating and capacitance—higher voltage and capacitance yield lower ESR. Marco's replacement of a 25V capacitor with a 400V unit reduced ESR from 6.2mΩ to 2.4mΩ, eliminating overheating. Low ESR is essential for reliable operation in high-current applications.

Equivalent Series Resistance (ESR) is a non-ideal property of batteries, capacitors, and other electronic components that represents their internal resistance. AA alkaline batteries have approximately 120 milliohms ESR, causing significant voltage drop and heat generation under high current loads. In contrast, ultracapacitors have extremely low ESR (0.7 milliohms), allowing them to deliver hundreds of amperes without substantial voltage loss or heating.

This video teaches how to design buck, boost, and buck-boost DC-DC converters by calculating inductor values using the formula L = (V × t) / ΔI, where V is the voltage across the inductor, t is the time the voltage is applied, and ΔI is the peak-to-peak current ripple; calculating capacitor values for continuous current mode using C = (I_ripple × T) / ΔV, where I_ripple is the current ripple and T is the switching period; and selecting components based on key datasheet parameters including saturation current, RMS current, voltage ratings, ESR, and thermal resistance, while emphasizing that PCB layout is critical for minimizing high dv/dt and high di/dt effects to reduce electromagnetic interference and improve efficiency.

This comprehensive section covers the full capabilities of a bidirectional buck-boost converter. The presenter demonstrates that the same circuit can operate as a buck (step-down) when input voltage exceeds output, or as a boost (step-up) when input voltage is lower than output. Crucially, the complete symmetry of the four-MOSFET H-bridge allows energy transfer in both directions between any side. The presenter outlines practical applications including solar panel to battery charging (lead-acid or lithium), super capacitor energy transfer between banks, and bidirectional energy management between different storage technologies. The section emphasizes that this versatility eliminates the need for separate converters for each application direction, representing a fundamental shift from unidirectional to truly flexible power conversion systems.

The buck-boost converter is a fundamental power electronics topology that generates a negative output voltage from a positive DC input voltage, with the output voltage magnitude being controllable through the duty cycle D (V_out = -V_in × D/(1-D)). The converter operates in continuous conduction mode with two alternating states: during on-time T_on, the input voltage charges the inductor linearly; during off-time T_off, the inductor discharges through the diode to the output, creating a negative polarity. The inductor current ripple ΔI_L = (V_in × D) / (L × f_sw) and capacitor voltage ripple ΔV_C = (V_out × D × (1-D)) / (f_sw × C × R_L) are critical design parameters that determine component sizing. A design example demonstrates how to calculate the required inductor value (24 μH) and capacitor value (69 μF) for a 24V to -12V conversion at 100 kHz switching frequency with specified ripple constraints.

A functional solar-powered energy storage system integrates three core components: a solar panel (2.4W at 17.5V), a super capacitor bank (six 120F capacitors in series providing ~16.8V), and a buck-boost converter (LTC3780). The system requires proper sunlight exposure for effective charging. Protection circuits use resistor pairs to dissipate excess power and prevent overvoltage. The buck-boost converter requires a minimum input voltage of 5V to activate output. Potentiometers control output voltage, current limit, and low-voltage lockout thresholds. Supercapacitors exhibit linear voltage drop proportional to state of charge, unlike batteries which maintain constant voltage during discharge. This fundamental difference necessitates using a buck-boost converter to maintain constant output voltage regardless of charge level.

Hybrid energy storage systems combine lithium-ion batteries with supercapacitors to optimize energy management by leveraging their complementary characteristics—batteries provide high energy density for sustained operation while supercapacitors deliver high power density for handling peak loads and reverse currents, thereby extending battery lifetime and improving overall system efficiency in applications like electric vehicles and industrial equipment.

Hybrid energy storage systems that combine batteries (high energy density) with supercapacitors (high power density) can simultaneously provide multiple grid services—such as frequency regulation, peak shaving, and solar smoothing—without oversizing the system, resulting in 25% cost reduction and 25-30% improvement in effective cycle utilization compared to single-technology solutions.

A Hybrid Energy Storage System (HESS) combines two or more energy storage technologies with complementary characteristics, such as batteries (lithium-ion, lead-acid) and supercapacitors, to provide optimal solutions that single technologies cannot achieve; this approach addresses the increased electrical load demands in modern transport vehicles by improving acceleration, drive efficiency, driving range, battery lifespan, and energy/power density while reducing lifecycle costs.

Lithium-Ion Capacitors (LICs) are hybrid energy storage devices that combine the high-power characteristics of supercapacitors with the higher energy density of lithium-ion batteries, featuring a cathode similar to supercapacitors and an anode similar to lithium-ion batteries; while LICs offer improved energy density (approximately double that of conventional supercapacitors) and faster charge/discharge capabilities (internal resistance of 50-100mΩ), they still cannot replace traditional batteries for general energy storage due to lower overall energy density, but excel as buffer components in applications requiring quick charge/discharge cycles such as electric vehicle regenerative braking systems, uninterruptible power supplies, IoT devices requiring long operational life, and harsh environment applications where safety is a priority.

This section introduces the research context of hybrid energy storage systems (HESS) for electric vehicles. It explains why lithium-ion batteries alone are insufficient due to limited life cycles affected by discharge rate, temperature, and voltage fluctuations. The solution involves coupling batteries with super capacitors, which offer higher specific energy than electrolytic capacitors but less than batteries, along with much higher life cycles and ability to handle fluctuating loads. The presentation covers four main HESS topologies: passive parallel connection (simplest, least expensive), semi-active super capacitor-battery topology, semi-active battery-super capacitor topology, and full active topology with two converters. The research focuses on converting internal combustion engine vehicles to electric vehicles using these hybrid systems.