Supercapacitor Bank Product

Overview

A Supercapacitor Bank is an ultracapacitor energy storage system designed for bridging power gaps and stabilizing voltage on distribution networks. Unlike battery systems, supercapacitors deliver exceptional power density (100+ kW/kg cell material) but lower energy density (40–60 Wh/kg), making them ideal for frequent charge–discharge cycling and burst power applications.

This module stacks eight 3.3V cells in series to reach 26.4V nominal, with integrated Balancing Board circuits that actively prevent individual cell overvoltage. Voltage imbalance typically occurs in series-connected ultracapacitors because cell leakage currents differ by 5–10%, causing some cells to charge faster than others. The active balancing topology uses shunt resistors and MOSFET Switch Module to reroute charge from higher cells to lower ones, keeping all cells within 0.1V of each other.

How it works

When the Supercapacitor Bank charges, current flows through the Cell Stack Assembly, which consists of cylindrical 3.3V 3000F modules connected in series by copper interconnect bars. Each cell stores energy as an electrostatic field in a double-layer capacitor interface. The Balancing Board monitors voltages across four parallel groups (two cells per group) via precision sensing inputs. If one group drifts above nominal (say, 3.5V), the Microcontroller fires a MOSFET Switch Module gate pulse, allowing that group's charge to bleed through a Shunt Resistor to the lowest group.

Power flows through the Bus Bars and Terminals, which consist of oxygen-free copper rails rated for 1000A peak. The Enclosure and Frame houses all subassemblies and provides thermal management via Thermal Management: two Blower Motor fans and aluminum Heatsink Assembly units that dissipate heat from the shunt resistor losses during balancing. A Monitoring Module module displays real-time voltage, current, and temperature on a touchscreen and logs all fault events.

The Disconnect Switches section includes a remotely-operated main Main Contactor and a manual Manual Disconnect Switch safety switch for maintenance isolation.

Charging and Discharging Curves

Charging is exponential: voltage rises from 0V to 26.4V following V(t) = 26.4(1 − e^(−t/RC)), where the RC time constant is 20–30 seconds at moderate charge currents (500A). Full charge to 99% takes roughly 90 seconds. Discharging is nearly linear due to constant-power loads: a 50 kW load draws the bank from 26.4V to ~13V in 10 seconds.

Balancing and Cell Safety

Cell voltage limits are 3.65V absolute maximum (beyond which the electrolyte begins to decompose). The Balancing Board uses a simple feedback loop: every 100 ms, the Microcontroller samples all four group voltages; if any exceeds 3.6V, it gates on that group's MOSFET Switch Module to shunt current through the resistor string. This drains the high group and raises the low group's voltage through resistive coupling, converging to equilibrium in 5–10 cycles. Continuous operation with this circuit adds <5% power loss.

Applications

Supercapacitor banks are used in three main domains: (1) grid-tied renewable buffers that store excess wind or solar for 5–20 second smoothing; (2) UPS and data-center ride-through, where they bridge the gap until a diesel generator spins up; (3) industrial regenerative braking, capturing kinetic energy from conveyor or elevator loads. Because supercapacitors do not age chemically like batteries, they tolerate millions of shallow cycles without degradation, making them superior for high-frequency micro-cycling.

Thermal Considerations

During a 100 kW discharge pulse lasting 10 seconds, the shunt resistor network dissipates approximately 200 W (assuming 5% internal losses). If the bank sits idle at 26.4V, leakage current through each cell (typically 1 mA per 1000F) causes passive thermal drift. The Thermal Management system is sized to maintain cell temperature below 60°C; in typical indoor environments (20°C ambient), passive convection alone is sufficient, but the fans activate if internal temperature sensors on the Balancing Board exceed 50°C.

Maintenance and Lifecycle

Supercapacitors exhibit virtually zero capacity fade over 1 million cycles if operated within voltage and temperature ratings. The main wear-out mechanism is electrolyte evaporation, which is negligible in sealed cylindrical cells. Annual maintenance consists of: (1) verifying Monitoring Module logs show no voltage imbalance trend; (2) checking Thermal Management fan operation; (3) visual inspection of Bus Bars and Terminals and Compression Lug Terminal for corrosion (unlikely with tin-plated copper, but verify).

Integration

The module connects to external circuits via a single Disconnect Switches pair of posts: positive and negative. A 500 µH series inductor (external) protects against fault transients. The Monitoring Module module includes a Modbus RTU or Ethernet gateway option for remote status integration with energy management systems.